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Colorado Blue Columbine

Scientific Name: Aquilegia coerulea; synonym Aquilegia caerulea

Short-lived perennial; 12-24”; shade, part shade, full sun at high elevation; well-drained sandy soil, loam, or light clay; tolerates dry shade.

Description: Colorado Blue Columbine, the Colorado state flower, is an upright herbaceous perennial in the Buttercup Family (Ranunculaceae) with large, showy flowers (2-4” across) and delicate divided leaves. It is native to the Rocky Mountains and is often called Rocky Mountain Columbine. Flowers most often have five creamy white petals surrounded by five blue petal-like sepals, but can actually be various shades of blue and white, lavender blue and white, or all creamy white. The five petals are elongated into graceful spurs that serve to hold the nectar. 

Colorado school children spearheaded a campaign in the late-19th century that resulted in the designation of this columbine as the official state flower in 1899. In its official role, the Colorado Blue Columbine symbolizes the state through its colors: the blue sepals represent the state’s clear blue skies, the center white petals signify the state’s snow-capped mountains, and the yellow stamens symbolize the state’s gold mining history. Aquilegia coerulea is protected by law that makes it illegal to dig out plants from public lands.

Height: 12-24″

Spread/Spacing: 8-24” / plant 12” apart

Exposure: Shade, part shade, full sun (Full sun best reserved for locations above 8000′, where it’s cooler.)

Soil Tolerances: Nearly any texture as long as it’s well-drained: sandy, loamy, light clay. Dislikes heavy clay. Any fertility: grows equally well in poor sandy soils or rich organic garden soils.

Soil Moisture: Any, depending on exposure. In general, likes it moist, but not wet. Less water is needed if planted in shady area; more water required if planted in full sun. (Best to not plant in full sun unless at high elevations.) Does fine in a dry, shady area, but will need watering in periods of drought or when soil 2-3″ below the surface becomes dry.

Water: Low to high, depending on sun exposure. Do not overwater.

Bloom: June - August, with repeat bloom throughout the season. 

Value to Pollinators: Nectar held in the flower’s slender spurs attract hawkmoths (hummingbird moths) and native long-tongued bees.

Deer & Rabbit Resistance: Yes. Also useful to know: all plant parts are poisonous if ingested by humans.

Where they like to grow: Beneath aspens or among red-twig dogwoods. Edges of forests; open meadows in the mountains.

Cultivation Notes: Easy to grow, reliable, and rewarding. Mulch is helpful for conserving soil moisture, but keep plant base clear so it does not rot. Remove spent flowers and water regularly to encourage repeat bloom. Avoid irrigation water on leaves to prevent powdery mildew. Can easily hybridize. To prevent crossing, plant only one species in the garden. Specimens are usually short-lived (2-3 years), but will often self-sow replacements. New generations’ flowers may have different colors due to hybridizing. Easily propagated by seed or not-so-easily by plant division. 

Photos: Magarete Steinhauer

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Golden Currant

Scientific Name: Ribes aureum

Shrub; 5-8’; full sun or part shade; well-drained sandy, loamy, or clay soil; drought tolerant

Description: Golden Currant (also called Clove Currant, Buffalo Currant, and Spicebush) is an attractive deciduous shrub valued for its beautiful foliage, clove-scented lemon-yellow flowers, and edible fruit. The shrub, which can live for 15 years or more, grows 5-8 feet in height and nearly as broad. The tubular flowers appear in clustered abundance in early spring, along with large, shallow-lobed, spring-green leaves. Later in the season the flowers are followed by orange, red, or reddish-black edible sweet-tart berries. The stems of Ribes aureum are smooth and without spines (unarmed). The genus name Ribes is derived from the Arabic ribes (acid tasting), alluding to the tart edible fruit. Aureum is Latin for “gold,” a reference to the flower color or possibly also the fall color of the leaves. Golden Currant is in the Gooseberry Family (Grossulariaceae).

Height: 5-8’

Spread/Spacing: Mature spread is 4-6’; plant 4-6’’ apart.

Exposure: Full sun to part shade

Soil Tolerances: Prefers well-drained, slightly acidic, organic-enriched soil, but tolerates poor-fertility soils and soils of neutral or slightly basic pH; tolerates a variety of textures: sandy, loamy, clayey. 

Soil Moisture: Low to moderate. Mature plants are very drought tolerant.

Water: Low, but will also tolerate periods of excessive water.

Bloom: April - May; lemon yellow

Pollinator value: Nectar and pollen for butterflies and bees.

Deer & Rabbit Resistance: Numerous reports suggest deer and rabbit resistance. 

Where they like to grow: Commonly found on dry slopes, in ditches or near streams, and sometimes along roadsides in the foothills and plains at elevations between 3500’ and and 8500’.

Cultivation Notes: Although this shrub prefers a slightly acidic, well-drained soil, and afternoon shade in hot summer conditions, it tolerates a wide variety of environmental conditions, from drought to excess rain, and can withstand a deficit of soil fertility. However, if summer temperatures exceed 85 degrees F for an extended period, the shrub may drop its leaves. Annual pruning is helpful to maintain a good shape and to encourage a healthy fruit harvest. 

A newly planted golden currant should be watered regularly, keeping the soil evenly moist. Mulching will help conserve moisture. Once a plant is established and reveals healthy new growth, decrease watering gradually, as a mature golden currant requires little moisture. After it is established, water only when the soil is dry, providing enough moisture to saturate the root zone. 

Photos: Margarete Steinhauer

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Indian Ricegrass

Scientific Name: Achnatherum hymenoides; (previously, Oryzopsis hymenoides)

12-24″; full sun; sandy, rocky, gravelly soils or dry loam; drought tolerant

Description: Perennial bunchgrass. This is a cool-season grass (growth cycle peaking in spring rather than summer) that grows in airy, vibrantly green clumps that are 12-24” tall. It develops delicate tan seedheads in summer that flutter in breezes and make for a lovely haze amidst other grasses and flowering plants. These seedheads persist through the fall and add interest to the winter landscape. Despite its delicate appearance, this grass weathers prolonged cold, high winds, intense heat, and drought exceptionally well. Its fibrous root system and adaptation to dry, coarse soils make it a top performer in erosion control and reclamation arenas, though this grass might be chosen for its beautification powers alone. In the wild, it often teams with needle-and-thread grass (Hesperostipa comata) to revegetate recently disturbed sandy sites.

Height: 12-24”

Spread/Spacing: 12”

Exposure: Full sun

Soil Tolerances: Prefers deep sandy or rocky soils. Also does well in well-draining silt loams and clay loams. Does not tolerate dense clay, consistently wet, or poorly draining soil.

Soil Moisture: Dry

Water: Low; good drought tolerance.

Bloom: Flowers insignificant. Foliage and seedheads of main interest. Medium-green foliage, tan in winter.

Pollinator value: Seeds and cover for birds, host plant for Skipper larvae.

Deer & Rabbit Resistance: No; leaves and seeds are a favorite of rodents and deer. Protect from grazing until fall of second growing season to increase likelihood that crowns will sprout new growth in spring.

Where they like to grow: Dry grasslands, semi-deserts, deserts. Often seen in Northern Colorado growing among fringed sage (Artemisia frigida), buffalograss (Buchloe dactyloides), needle-and-thread grass (Hesperostipa comata), bush sunflower (Helianthus pumilus), mountain mahogany (Cercocarpus montanus), and soapweed yucca (Yucca glauca).

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Harebell; Bluebells of Scotland

Scientific Name: Campanula rotundifolia

6-24″; full sun or part shade; rocky, gravelly, sandy or clayey soil; drought tolerant

Description: Harebell is a delicate-looking plant that has nodding, bell-shaped lavender-blue blossoms arranged like bluebells on slender, graceful stems that carry narrow, 1-2” leaves. The scientific name refers to the plant’s bell-shaped flowers (Campanula = “little bell”) and round basal leaves (rotundifolia). You might not see the round basal leaves, because they often wither away by the time the plant flowers. It blooms throughout the growing season from spring to frost. In the wild, you may see single specimens, small clusters of a few plants, or large colonies that give meadows a purplish cast. It spreads and naturalizes when planted in conditions it likes. Perennial.

Height: 6-24” (usually about 12”)

Spread/Spacing: 12-15”

Exposure: full sun or partial shade (grow best with morning sun and afternoon shade)

Soil Tolerances: rocky, gravelly, sandy, well-drained;  most soils, even clay

Soil Moisture: medium-dry to dry

Water: low to medium; excellent drought tolerance

Bloom: June-September, purple or lavender-blue; Dead-heading spent flowers spurs more bloom.

Pollinator value: nectar and pollen for bees and butterflies; attracts hummingbirds

Deer & Rabbit Resistance: Rabbits leave it alone; Tolerates the rare browsing by deer.

Where they like to grow: rocky slopes, grassy slopes, crevices, open woods, meadows, rock gardens; foothills to alpine.

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Blue Grama

Scientific Name: Bouteloua gracilis

4-16”; full sun or light shade; variety of well-drained soils; drought tolerant

Description: This hardy warm-season bunch grass called “blue grama” is Colorado’s official state grass and a wonderful native plant for garden interest nearly all year long. The simple, slender leaves are bright green to bluish green in summer with noticeable and numerous seedheads that resemble eyelashes and later eyebrows as they dry and curl in the fall.  The shape of the seedheads gave rise to common names such as “eyelash grass” and “lamb’s eyelashes.” The plant turns tan in dormancy and the seedheads remain into fall and winter, giving structure and texture to the landscape and forage for wildlife. (See picture of appearance in fall below.) Blue grama is a treat for many creatures, providing shelter and seeds for birds and small mammals and nutritious forage for wild and domestic grazing animals. This native grass is also a host plant for satyr and skipper butterflies, and bees have been spotted on the purplish flower spikelets in late summer, when many other flowers have disappeared and gone to seed. People often call this “plant blue grama grass,” but it is more correctly called simply blue grama, as adding “grass” can be seen as redundant. “Grama” itself is an American-Spanish word (derived from Latin) meaning “grass,” specifically, a type of grass of the genus Bouteloua.

Blue grama tolerates some foot traffic and even a little shade, so it can provide a low-water, low-maintenance native alternative to typical turfgrass. Though it is a bunchgrass and, therefore, has a clumping habit, it combines nicely with buffalograss (Buchloe dactyloides) for an interesting native lawn. This pairing is common in the Northern Colorado wild and, therefore, looks natural and supports local insects and wildlife. This versatile plant is also pleasing as an ornamental grass (particularly the larger, cultivated variety known as ‘Blonde Ambition’), or as part of a wildflower prairie garden or native pasture.  Blue grama grows at elevations from 3,200 to 9,700 and has a huge root system that helps control erosion and benefit soil health.  Good for naturalizing, it spreads readily and can be divided. As this is a warm-season grass, it greens up in late spring. If you like tidier plants, the brown previous year’s growth can be cut off by hand or with an electric hedge trimmer in mid- to late-spring before the new shoots put on much growth. Cut back to 4-6″ above the base of the plant, or just above any new shoots you see.

Height:  Much variation here; 4-16” for naturally occurring varieties, or up to 36” in the case of the popular, taller-growing nursery selection called ‘Blonde Ambition.’  For wild varieties, the grass blades rise to only about 4″, with stalks bearing seedheads accounting for an additional 6″ to 12″ in height.

Spread/Spacing: Plants spread 10-18” in the wild. Plants grown from native seed should be planted 18” apart. The common nursery offering ‘Blonde Ambition’ (a cultivated variety, or “cultivar”) grows taller and wider, and has a spread of 30-36.” Specimens of this cultivar should be planted 24-36” apart. 

Exposure:  Sun to light shade

Soil Tolerances:  Prefers low-fertility, gravelly, sandy loams or clay-loams. Must be well-drained soil. Tolerates some clay or sandy soil but not pure clay or sand.

Soil Moisture:  Dry

Water: Low to moderate; may go dormant and turn tan in drought. Very good drought tolerance.

Bloom: June-August; tiny reddish-purple florets that can give a field or patch a purplish cast. Late summer brings small, decorative seedheads resembling eyelashes; they curl as they mature to look more like eyebrows and remain on plant as it goes dormant in fall.

Pollinator value:  Blue grama provides shelter and forage for insects, birds, and mammals.  The grass is a host plant for satyr and skipper butterflies. Bees are attracted to flower spikes for pollen in late summer, although the plant is pollinated by wind.

Deer & Rabbit Resistance:  No, but blue grama may be grazed after the growing season without damage to the plant. The grass retains high nutrient value even after drying and is a boon to both wild and domestic grazing animals.

Where they like to grow:  Found on the Great Plains of the U.S. and Canada, blue grama is a great native plant for sunny gardens or landscapes located in areas that were once short-grass prairie.

Cultivation Notes: Lower-growing varieties of blue grama can be planted by seed or small plugs to fill in larger spaces. It combines well with low-growing native wildflowers and buffalograss. The larger blue grama cultivar ‘Blonde Ambition’ mixes nicely with taller native wildflowers and is offered by garden centers in pots of different sizes for transplanting. Moisture and sun conditions may also influence the mature size of blue grama; the largest plants benefit from being cut back in late spring, just as new green shoots are beginning to emerge.

Photo credit (top): Flowering specimen at River’s Edge gardens by Kathy Maher

Photo credit (bottom): Patrick Alexander from Las Cruces, NM - Bouteloua gracilis, CC0, https://commons.wikimedia.org/w/index.php?curid=94220967

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Curlycup Gumweed; Rosinweed

Scientific Name:  Grindelia squarrosa

Biennial or short-lived perennial; 12-36”; full sun or part shade; wide range of soils; drought tolerant

Description: Curlycup gumweed and its look-alike close relative subalpine gumweed (Grindelia subalpina) are cheerful, yellow-flowering biennial or short-lived perennial plants native to Northern Colorado and throughout the Rocky Mountain range. The subalpine species sticks to the western foothills and mountains, but curlycup’s distribution extends to most of North America. These gumweeds (also called rosinweed and tarweed) are attractive “weeds” that offer plenty of ecological and medicinal benefits. They are prolific reseeders, however, and their progeny sometimes needs to be edited from kept gardens. Specimens in the Demonstration Gardens at River’s Edge Natural Area in Loveland occur there naturally; none were deliberately seeded there or planted. Curlycup gumweed’s growth habit is quite shrubby, but it is a herbaceous plant, meaning its stems remain fleshy and don’t become woody. All above-ground plant parts are aromatic and covered with glands that ooze sap. Leaves are often found glistening in the ooze and the plant’s upright stems exude a sticky, milky sap when cut open. Beads of the gummy sap also accumulate on flower heads before they open. So it’s clear why it’s called gumweed. The “curlycup” part of the common name refers to the curling bracts all over the “cups” (involucres) enclosing the flower buds. These numerous, small, thin, curling bracts make the buds resemble burdock, but gumweed buds are not prickly at all. 

As a biennial, this plant normally has a two-year life cycle, but it sometimes lives only 1 year or, conversely, 3 or more years. Leaves of a plant in its first year are all basal (arising from the lowest part of the stem close to the ground). These basal leaves are simple and mostly oblong, 2”-4+” long and 0.25”-0.50” wide, with margins (edges) that can be smooth, deeply lobed, scalloped, or coarsely toothed with glandular tips. Leaves along later-developing upright stems are oblong to oblanceolate, 0.5”-3” long and <0.75” wide, with coarsely toothed margins, clasping leaf bases and no leaf stalks. These leaves are covered with glandular hairs on both surfaces, and arranged alternately on the stem. Leaves on flower-bearing stems are smaller than basal leaves. All leaves are aromatic and contain glands that secrete a sticky substance.

Sunshine-yellow flowers start opening in July for a lengthy bloom period that usually winds down in September, but can continue through October. The 1”-1.5” blooms are actually “composite” flowers, made up of a cluster of tiny yellow disc flowers and the yellow petalled ray flowers that surround them. Numerous tiny tubular disc florets form the flower’s compact circular “button” center, with the 0.5”-long petals of 20-40 ray florets encircling the center and radiating outward. The sepals are reduced to awned pappus. The ovary of each floret is inferior and is positioned below the point of sepal and petal attachment.  Each flower head is supported and enveloped by a hemispherical involucre “cup” composed of numerous green, reflexed (bending backward), glandular, imbricate (overlapping) bracts that secrete a sticky substance; involucres (cups) are 0.25”-0.50” in diameter. The receptacle of the involucre is naked and smooth. Several flower heads are arranged in clusters at the ends of branches. 

Fruits are smooth, cream to gray-colored, oblong, four-sided, and deeply ridged small achenes, approximately 0.125” in length.

Height:  1’ - 3’

Spread/Spacing:  18-24”; space or thin to 3 feet apart

Exposure: Full sun to partial sun for several hours each day.

Soil Tolerance: Grows in a wide range of soils in open sunny areas. Common in disturbed areas with sandy, rocky, or gravelly soils, but also grows well in silty clay loam or sandy loam.

Soil Moisture: Moderately dry to very dry. Plant will tolerate periods of drought.

Water: Low. Rarely requires irrigation. Established plants will tolerate prolonged drought.

Bloom:  July-October; bright sunshine yellow 

Value to Pollinators:  Highly attractive to many native bee species, catering to some 40 genera, according to a 2016 ARS Bee Research Laboratory report. For example, this plant provides nectar and pollen to native Agapostemon species (green metallic sweat bees), Megachile species (leafcutter bees), and Melissodes species (long-horned bees). It also serves the non-native Apis mellifera (honey bee), though it’s felt it yields inferior-tasting honey. Many species of butterflies are also attracted to gumweed.

Deer & Rabbit Resistance: Yes

Where they like to Grow: Disturbed areas, alluvial grounds, overgrazed prairies, pastures, rangelands, roadsides, sometimes forming large patches. Very common in dry open places at elevations ranging from 3,500’ to 8,500’. Disturbed ground is their favorite territory. Often joins cheatgrass in vegetating disturbed areas. (It’s no wonder gumweed took up residence in the demonstration gardens at River’s Edge Natural Area as we were digging up and replanting those areas.) 

Other Interesting Notes: Throughout the ages, people have reportedly chewed the resinous sap collected from leaves and flowerheads like gum. Fruits are consumed by some birds; this plant has been observed to be a minor source of forage for sage-grouse chicks. It is otherwise considered undesirable forage and is unpalatable to livestock. The people of many Native American nations used this plant to make healing solutions, ointments, and poultices; tea for relief from asthma, cough, and tuberculosis; and brooms fashioned from stems stripped of their leaves. These peoples knew the medicinal value of this plant. Teas were made from the resinous flowerheads and from the leaves. The flowerhead tea was taken to relieve indigestion, colic, and stomachaches. The leaf tea was a useful antispasmodic for dry, hacking coughs, and was therefore used to treat throat and lung problems such as coughs, bronchitis, and asthma. They used a tincture made from flowerheads in treating bladder and urethra infections, and applied gumweed-based teas and tinctures topically to heal minor cuts, abrasions, and pimples. Flowerhead tinctures or crushed-flowerhead poultices were used to soothe and heal skin irritations such as those caused by poison ivy and poison oak.

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Lewis Flax; Native Blue Flax

Scientific Name: Linum lewisii

18”; full sun to part shade; sandy soil, rocky soil, loam, light clay; very drought tolerant

Description: Lewis flax, also called native blue flax, is native throughout the western United States and Canada and is found growing wild as far east as Louisiana, Minnesota, and Ontario. It is named after Captain Meriwether Lewis, whose expedition (1803-1806) with Second Lieutenant William Clark had documenting plant species among its objectives. Lewis flax is a common wildflower in Northern Colorado and can be easily grown in residential landscapes. It is usually available at local nurseries that stock native plants, but try to confirm the scientific name of the species sold is Linum lewisii and not Linum perenne (perennial flax), which is a nearly identical species native to Europe. (Since its introduction to North America hundreds of years ago, Linum perenne (perennial flax) has naturalized itself across most of the continent and is difficult to distinguish from Lewis flax.)

This is an attractive early bloomer that grows to 18” or so with vase-shaped habit. It is considered semi-evergreen because some leaves at the base of the plant remain green through the winter. 

Its slightly arching stems appear delicate, but are remarkably tough. (A close relative is the flax* that produces the fibers that linen is made from.) Stems become semi-woody with age. They are covered with short, narrow, deep-green leaves from top to bottom and their tips nod at the ends where the flower buds form. Flowers range in color from an ethereal pale blue to a strikingly rich sky blue and, when plants are in bloom, a patch of them in a distant meadow will give the area a distinctly blue cast. Individual flowers only last a day, but mature plants bloom profusely over a long period. Plants can bloom on and off all season, but more commonly will have their main bloom in May and a second, lighter bloom in July. 

Lewis flax is a low-maintenance, low-water plant that does exceptionally well in dry, poor, non-irrigated soils. Transplants won’t need supplemental water after about 8 weeks in the ground, unless the season has prolonged dry spells (more than a month without rain). Self-sown and direct-sown seedlings do amazingly well without supplemental water. 

This is a short-lived perennial. Individual plants may last only 2-3 years, but they tend to self-sow prolifically, so there are always new generations coming up. If a specimen hasn’t sent new green shoots up by the end of April, it’s dead and can be removed. There will likely be volunteer seedlings to take its place. If you don’t particularly like where the volunteers have chosen to take root, you can transplant them to better locations after they’ve grown to be 2-3” tall. Do your transplanting on a cool, cloudy day to make the transition easier on the seedlings. Transplanted seedlings will need to be watered regularly until they are established in their new location.

Lewis flax plants and seeds contain cyanogenic compounds that can produce cyanide as they are broken down through digestive processes. This makes them toxic to cattle, sheep, and goats. Deer and rabbits largely ignore this plant. The seeds can be eaten by people, but only after they’re cooked to reduce toxicity. 

*Lewis flax is also a close relative of the Eurasian native Linum usitatissimum, which is an annual species known as “common flax” that has been cultivated for thousands of years for its fiber (linen), seeds (nutrient-rich flaxseed), and seed oil (linseed oil). Small wonder the Latin word usitatissimum was chosen to name that species: it means “most useful.”

Height: 18”

Spread/Spacing: 12” / plant 12-24” apart

Exposure: Full sun or part shade

Soil Tolerances: Prefers infertile, dry soils. Soil textures can be sandy, rocky, loamy, or clayey. Tolerates light clays, but some sources report that the plant does not do well in dense clay. 

Soil Moisture: Dry

Water: Low; Excellent drought tolerance.

Bloom: May-July; various shades of blue

Value to Pollinators: Pollination ecologists report that this species is of special value to native bees, attracting large numbers of them.

Deer & Rabbit Resistance: Yes. Deer and rabbits usually leave this plant alone, but mice and voles sometimes go after shoots of very young plants, especially seedlings transplanted from nursery pots. These plants are tough and can withstand considerable abuse, but you may want to protect young transplants for a few weeks with a ring of hardware cloth or similar until they reach about 8” in height. 

Where they like to grow: Open areas, disturbed areas, meadows, rocky prairies, rocky woods, dry hillsides. Often found in plant communities with mixed grass, sagebrush, mountain brush, and aspen trees.

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Showy Milkweed; Common Milkweed

Photo by Matt Lavin* (more information below)

Scientific Name: Asclepias speciosa

18-48”; full sun; gravelly clay, loamy or sandy soil; drought tolerant

Description: Showy (or common) milkweed is an herbaceous, upright, coarse-textured perennial plant that develops showy, fragrant pinkish or purplish ball-shaped flower clusters in May and June. The plant’s stout stems grow rather tall (to about 30”), rarely form branches, and carry a milky latex sap. Leaves are 4”-7” long, oblong or oval, with prominent veins, smooth edges, and covered soft woolly hairs on both top and bottom surfaces. The leaves are often almost twice as long as wide and will also leak milky sap if cut. 

Flowers of milkweed species are some of nature’s most complex, and showy milkweed offers a good example of this complexity. Its pom-pom-like clusters spanning 3-4 inches in diameter appear greenish-pink or greenish-purple from a short distance, with each cluster comprising numerous half-inch flowers. Each delightfully fragrant flower is composed of 5 reflexed (bending downward) sepals, 5 reflexed petals, 5 stamens united to the petals and to the 2 united pistils to form a gynostegium which forms “pinch-trap flowers.” The ovary is superior and is positioned above the point of sepal and petal attachment. The 2 club-shaped anthers of the united stamens produce sticky grains of pollen that clump together in masses called pollinia. These pollinia are connected to each other by a thread-like structure called a translator, which connects to a membranous disc-shaped gland with a slit in it. The connected pollinia are tucked within the gynostegium, such that the slit of the gland is easily accessible to visiting pollinators. The reflexed sepals are usually purplish-green to pinkish-purple in color. The reflexed petals are usually purple to pink, but are sometimes white in color. Between the petals and the stamens there are pink- to cream-colored petal-like appendages called coronas, which arch upward and form a hood over the adjacent stamens. “Horns” extend from the bases of the hoods and this hood-and-horn structure makes the upper part of the flowers look like tiny crowns or stars. 

The fruit (seed pod) is an elongated spindle-shaped, pod-like follicle, that grows to 3”-4” long, has soft spiny projections, and is covered with soft woolly hairs. The seed pods become leathery and split open when mature. Each pod contains numerous reddish-brown flat, oval seeds with winged margins. A tuft of silky hairs is attached to each seed.

All plant parts exude milky latex sap when cut. The raw sap contains cardiotoxic compounds which can be harmful to grazing/browsing mammals. However, there are numerous references to milkweeds being consumed for food by indigenous peoples, early settlers, and modern-day wild food foragers. Because heat deconstructs or destroys the toxic compounds, it is essential to cook any part of a milkweed plant before eating it.

Height: 18-48”

Spread/Spacing: 30-48”

Exposure: Full sun or strong sun for at least a few hours a day.

Soil Tolerances: Grows in a wide range of soils ranging from gravelly-clay to loamy and sandy soils.

Soil Moisture: Moist to moderately dry.  After establishment, plant will tolerate periodic drought.

Water: Low to Moderate. Requires occasional irrigation in dry spells. Established plants will tolerate periodic drought.

Bloom: May-June; Greenish-pink or greenish-purple 

Value to Pollinators: Provides nectar and pollen to numerous species of bees, including Apis mellifera (honey bee); wasps; flies; butterflies, including fritillaries and swallowtails; beetles, especially Tetraopes spp. (milkweed beetles); and hummingbirds. This and other species of Asclepias are host plants for larvae of the Danaus plexippus (monarch butterfly), Danaus gilippus (queen butterfly), and Danaus eresimus (soldier butterfly), as well as Cycnia inopinatus (unexpected cycnia moth), Cycnia tenera (dogbane tiger moth), and Euchaetes egle (milkweed tussock moth).

Potential risk to some pollinators…the pollinia!  When an insect attempts to obtain a foothold on a smooth flower it is likely to put an antenna, leg, or tongue through the slit of the connected pollinia. When the insect moves it is likely that the pollinia will become clamped onto that part of the insect. If the insect successfully pulls away from the flower, it will carry the masses of pollen with it. Then when the insect alights on another milkweed flower, the pollinia are thrust into the gynostegium, where the masses of pollen come into contact with the stigma. However, once inserted into the gynostegium and pulled upwards, the pollinia cannot be withdrawn. At that point, the insect can only be liberated when then the connecting translator is broken. If that connection is not broken, the insect remains trapped on the flower, eventually perishing from exhaustion and starvation. Sometimes honey bees can be found in the hive with pollinia attached to their antenna, legs, or tongue!

Deer & Rabbit Resistance: Yes

Where they like to grow: Prairies, plains, foothills, and mountains at elevations ranging from 3,400’ – 8,600’. Common along roadsides, ditchbanks, pastures that have not been over-grazed, fencerows, edges of cultivated fields, open coniferous forests. Large patches form by spreading rootstocks when plants are not disturbed by tillage practices.

Additional Interesting Notes:  This is the most abundant species of milkweed in Colorado. Plants provide nesting sites and cover for birds. Small mammals line their nests with the silky hairs attached to the seeds. Silky hairs have been and can be used to stuff comforters, mattresses, and pillows; and can be woven with other fibers into cloth.  All RAW parts of the plant are poisonous due to the presence of cardiotoxic compounds. Young shoots, flower buds, and young fruits are edible, but MUST BE COOKED prior to consuming. Peoples of several Native American nations as well as modern-day wild plant foragers prepare young plants like asparagus and the young firm pods like okra. The flower buds and newly opened flowers were and can be boiled down to make a thick sweet syrup or brown sugar; they have also been made into preserves. Seeds were also eaten.

Flowers secrete nectar over numerous weeks. Honey made from milkweed flower nectar is thick, mild in flavor, and almost white in color (frequently with a yellowish tinge). The beeswax honeycomb is pearly white. The flavor is excellent, with a slight tinge that becomes milder with age.

Peoples of several Native American nations used this milkweed for several medicinal purposes, including treatments for skin problems such as moles, ringworm (a fungal infection), and warts; making ointments and salves for healing burns and other wounds, and for soothing rash caused by poison ivy. Infusions or teas were made from various parts of the milkweed plant for treatment of arthritis, asthma, congested lungs, digestive tract disorders, intestinal worms, and venereal diseases.

*Photo Credits: Top photo by Matt Lavin from Bozeman, Montana, USA - Asclepias speciosa  Uploaded by Tim1357, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=22756394

Bottom photo: Madeline Maher

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Tansyleaf Tansy-Aster; Tansy Aster; Tahoka Daisy

Scientific Name: Machaeranthera tanacetifolia

Annual or Biennial; 10-28”; full sun or light shade; sandy or rocky soil; drought tolerant

Description: Tansyleaf tansy-aster is an annual or biennial wildflower that is native to northern Mexico, the southwestern U.S., and dry, sandy soils and rocky areas of Colorado, Wyoming and Montana. Its lovely flowers have bright purple petals surrounding a central yellow disc. The Greek word Machaeranthera identifying the genus refers to the flower’s sword-shaped and sharp-pointed anthers (the parts of a flower containing pollen). Its Latin species name tanacetifolia means “fern-like leaves.” Individual leaves are deeply divided into many narrow segments. Their spiny tips make it easy to distinguish tansyleaf tansy-asters from other asters. Mature plants have a bushy appearance. 

Tansyleaf tansy-aster’s bright purple flowers make a great addition to the late summer or fall garden. Like other purple asters, it is particularly effective when planted with yellow flowering plants that bloom at the same time, such as yellow asters and other members of the sunflower family, Senecio spp., rabbitbrush and snakeweed.

This beautiful wildflower is also known as Tahoka Daisy, because it was discovered growing near Lake Tahoka, Texas in 1898. Seed packets have been carried by members of the Tahoka Rotary Club to conventions all over the US and overseas. To this day, the City of Tahoka will provide one seed packet without charge when requested by e-mail.

Height: 10- 28”

Spread/Spacing: Plants sprawl up to 3 feet or more when mature.

Exposure: Full sun, light shade

Soil Tolerance: Sandy, gravelly, or rocky soil in dry open areas.

Soil Moisture: Dry to moist, excellent drought tolerance.

Water: Low to medium

Bloom: May - September

Pollinator Value: Butterflies, bees and other insects

Deer & Rabbit Resistance: Resistant to deer because of prickly foliage.

Where they like to grow: Deserts, sandy or rocky plains, dry open areas, well-drained areas in valleys.

Cultivation Notes:  Plants are not widely available and are usually started by seed. Seeds can be planted in either spring or fall. They should be scattered directly on the surface and covered lightly (1/16″ of light cover). Keep seeded areas moist until seeds sprout. Seed may be harvested when ripe in the fall and planted where desired. Successive generations of this annual/biennial may sprout in scattered, nearby areas from wind-blown seed. 

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Sticky Purple Geranium; Cranesbill

Scientific Name: Geranium viscosissimum [G. nervosum]

18-30”; full sun, part shade; loam, sandy loam, clayey loam; drought tolerant

Description: Sticky purple geranium is a mounding perennial plant with one or more stout, upright, branching stems that sport pinkish-white to deep-magenta blooms in spring and summer. The stems have a clear sap. This is an herbaceous plant, meaning its above-ground stems remain fleshy and don’t turn woody. All plant parts are covered with sticky yellow-tipped glandular hairs. 

Leaves are hairy on top and bottom, thick-textured, mostly basal (arising from the base of the plant), 2”-6” long and wide, and have 3, 5, or 7 palmate lobes (radiating outward from a central point on the leaf like fingers of a hand). The lobes are pointed and deeply toothed. Leaf stalks are long, with small triangular leaf-like appendages at the petiole base (where leaf stalk attaches to plant stem). Leaves on stems that bear flowers are smaller than basal leaves. Leaves turn reddish in late summer or early fall.

Each attractive flower is 0.75”-1.5” in diameter; and composed of 5 sepals with pointed tips, 5 petals, 10 stamens, and a stylar column composed of 5 united styles, 5 stigmas, and a 5-lobed ovary. The stylar column provides the path through which pollen moves to fertilize the 5 ovules in the ovary; these ovules then develop into 5 seeds. The ovary is superior and is positioned above the point of sepal and petal attachment. After fertilization, as the fruit matures, the stylar column elongates, so as to resemble the bill of a crane, with the ovary being the head. It is this characteristic that gave rise to the plant’s common name “cranesbill.” The sepals are green in color and covered with glandular hairs. The petals can be pale pink, pale purple, or deep magenta in color, with dark pink or dark purple longitudinal stripes that function as nectar guides for visiting pollinators. Each flower is attached to a 0.5”-1.5” stalk, and few to several flowers are arranged in loose clusters at the tips of long branched stalks and in upper leaf axils.

The unique elongated, “crane’s bill” fruit is a distinguishing characteristic of plants in the Geranium (Geraniceae) family. Sticky geranium’s fruit is an elongated schizocarp that lengthens as it matures. (A schizocarp is a fruit that splits into separate seed compartments as it matures.) At maturity, the sepals subtending the fruit bend backward, and the dry elongated fruit splits longitudinally into 5 sections, such that each section coils the length of the style, with a single seed attached at the basal end. Each dried, coiled style remnant resembles a small corkscrew, which functions as a drill to embed the seed into the soil. The drilling action is triggered by changes in atmospheric humidity. 

Height:  18” - 30”

Spread/Spacing:  18” - 24”

Exposure: Full sun to part shade. Does best in diffused sunlight, especially when planted in hot areas or drier soils. Too much shade (or water) causes sprawling spread.

Soil Tolerance: Grows in a wide range of soils, ranging from moist, loamy soils to dry clayey alkaline soils. Prefers loam, sandy loam, or clayey loam. Tolerates gravelly soils, but will probably require supplemental water. 

Soil Moisture: Moist to moderately dry.  After establishment, plant will tolerate periodic drought.

Water: Low to Moderate. Requires occasional irrigation during dry spells. Established plants will tolerate periodic drought.

Bloom: May-August; pinkish-white, pink, pale-purple, or deep magenta-purple; petals of all colors have darker pink or darker purplish veining.

Pollinator Value: Provides nectar and pollen to numerous species of bees, including Andrena spp. (mining bees), Apis mellifera (honey bees), Augochlora spp. (wood-nesting green metallic sweat bees), and Bombus spp. (bumble bees), as well as many species of butterflies. Also visited and pollinated by various species of flies.

Deer & Rabbit Resistance: No. Expect damage, but specimens usually recover, even from being grazed to the ground. This plant is sought after by several species of animals which eagerly consume the tasty leaves and flowers; elk and moose are reported to be especially fond of eating the flowers.

Where they like to grow: Native to mesic prairies, scattered throughout open woodlands, in meadows, on mountain slopes, and along streams. Common in middle to subalpine elevations ranging from 6,500’ to 10,000’, but also grows at elevations as low as 1000′.

Additional Interesting Notes: Considered to be good forage for sheep. Leaves and roots are used as herbal remedies to reduce inflammation. Fun fact: Like many sticky plants, sticky geranium is “protocarnivorous,” meaning it is able to partially “digest” insects that get stuck on plant surfaces, breaking down protein in bug bodies and absorbing nitrogen derived from the process. 

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Great Plains Yucca; Soapweed

Scientific Name: Yucca glauca

16-24”; full sun or part shade; any well-drained soil; drought tolerant

Description: This native, perennial, evergreen shrub is an icon of Western landscapes and is immediately recognizable by its dense clump of sword-like, grayish-green leaves radiating from a central rosette. In northern Colorado, it’s as common as the rabbitbrush it grows beside -- and, if you have the space, that’s an archetypal northern-Colorado pairing worth replicating in your northern-Colorado yard or garden! Soapweed yucca’s leaves are stiff and dangerously sharp, but installed at a distance from play areas and set back somewhat from walkways, they make a striking architectural statement in the landscape. These shrubs are particularly stunning in bloom, with flower stalks covered in huge creamy-pinkish-white or creamy-greenish-white bell-shaped blooms rising 3-4 feet or more. Once established, this plant is a star performer needing little to no supplemental water and little to no maintenance. Short rhizomes (underground horizontal stems) often sprout offsets (side shoots that start new plants) close to the base of the mother plant, creating dense clusters of 2-5 specimens. The offsets can be removed when small and planted elsewhere, or they can be left in place for a more natural appearance. After several years the mother plant will die off and one or more offsets will remain to continue the circle of life. The species name “glauca” zeros in on the plant’s notably grayish leaves. The English word ”glaucous” (meaning “of a dull grayish-green or -blue color” or “covered with a powdery film”) comes via Latin from a Greek word meaning “gleaming” or “gray.” In botany, “glauca” refers to the characteristically grayish or bluish cast of a plant, owing to a fine, whitish, waxy or powdery coating on its leaves or stems. And if you’re wondering why this shrub is commonly called soapweed: This yucca’s thick, tuberous roots contain a high concentration of saponin, which is a compound used in soaps and detergents that foams when agitated in water. A natural DIY soap or shampoo can be made by cleaning, peeling, chopping, and crushing the roots of this yucca and mixing with water. Some people enjoy eating the raw or cooked flowers, fruit, seeds, and the innermost part of the flower stalks of this plant, but the roots are not eaten, due to the high (toxic) saponin content. (The “yucca root” you find in stores is not true yucca.)

Height: 16-24”

Spread/Spacing: 24-36”; plant 3’ apart.

Exposure: Full sun or part shade. (Also, seriously windy spots are fine; this plant can take it.)

Soil Tolerances: Prefers dry, low-fertility, rocky soils, but adapts well to any sandy, loamy, or clay soil that drains well. Not fussy about pH level, adapting to acid, neutral, or basic soils.

Soil Moisture: Dry

Water: Low; excellent drought tolerance.

Bloom: June-July; creamy pinkish- or greenish-white.

Value to Pollinators: Provides cover, food, and nesting material for birds and has a symbiotic relationship with the yucca moth. The yucca plant and yucca moths need each other to survive. According to the U.S. Forest Service, the yucca moth is the only insect that successfully pollinates yucca flowers, and the yucca fruit is the sole food source for yucca moth larvae.

Deer & Rabbit Resistance: Fair; flowers require protection. The sharp-tipped blades are largely ignored spring through fall, but deer can’t resist the flower buds and open blossoms. (Case in point: Bitten-off buds in picture above.) As soon as buds begin to appear, you may want to start spraying the flower stalks with an eco-friendly repellent to prevent deer from devouring every last blossom. Leaves have low palatability, but, when other food is scarce in winter, mule deer and other mammals will eat the them, sometimes gnawing every single leaf-spear right down to its base. The denuded central stems will sprout new growth the following spring.

Where they like to grow: Dry plains, short-grass prairies, sandy hills, desert grasslands, rocky foothill shrublands. Common in northern-Colorado plant communities with rabbitbrush, prickly pear cactus, mountain mahogany, snakeweed, buffalograss, blue grama, and little bluestem.

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Golden Columbine

Scientific Name:  Aquilegia chrysantha

18-36”; full sun, part shade, full shade; loam, sandy, or rocky soil; drought tolerant

Description:  Golden columbine is one of many species in the Aquilegia genus of the Buttercup family (Ranunculaceae).  The yellow flowers of Aquilegia chrysantha are quite large and numerous and have yellow sepals and spurred yellow petals. The long spurs, which are part of the modified petals, developed in response to their main pollinators, hawkmoths. The name columbine comes from the Latin word for dove, and refers to the flower’s spurs, which were thought to resemble a cluster of five doves. Golden columbine’s leaves are bright green and divided. Its flowers appear both strikingly unusual and delicately pretty, with a fairy-garden look about them. The shade of yellow may vary, with some golden columbine varieties having greenish yellow blooms and others creamy yellow, two-toned, or lemon-yellow flowers. Plants are bushy and about 1-1/2 to 3 feet in height and about 18 inches wide. They will reseed to form colonies if they are happy with conditions. Gardeners will find them to be tough and adaptable to many locations, including full shade, and even drought-tolerant when protected from extreme heat and sun and planted in well-draining soil. Although not native to Larimer County, golden columbine is found in El Paso County in Colorado. In the home landscape, golden columbine adds lightness and colorful bloom to a shade garden, helps naturalize areas, can provide a meadow effect underneath a tree, and beckons pollinators to the location. This plant is a great choice for shady, dry areas under trees where little else wants to grow.

Height:  18-36”

Spread/Spacing:  18” spread; plant 18-24” apart

Exposure:  Golden columbine grows in shade, partial shade and full sun, but does best with at least some afternoon shade or dappled sun. Stress from extreme heat and sun makes it vulnerable to insect infestation.

Soil Tolerances:  Prefers loam, but can adapt to sandy or rocky soil or even clay if amended with compost. Well-draining soil is essential; susceptible to crown rot in poorly draining sites.

Soil Moisture:  Varies with sun exposure, but prefers moist soil (not wet).

Water:  Water needs are low, but vary depending on sun exposure.  Golden columbine is tolerant of heat and very low water but may go dormant in drought. Additional water in extreme heat may help prevent this. Too much water makes stems floppy.

Bloom:  Blooms from April into September, with charming yellow flowers.  A little extra water during heat waves encourages repeat blooming.

Pollinator value:  Golden columbine is an attractive food source for bumblebees, butterflies, hawkmoths, and hummingbirds. 

Deer & Rabbit Resistance:  Resistant to both.  All parts of the plant are poisonous.

Where they like to grow:  Moist canyon and streamside locations and in the understory of aspen and conifer groves in parts of Arizona, New Mexico, Texas, Utah, and El Paso County, Colorado. Thrives at elevations from 3,000 to 11,000 feet. Adaptable to many spots in the home garden.  

Cultivation Notes:  Considered by some to be the easiest to grow and most long-lived of the Columbines for Colorado.  Prefers soil to be moist in spring, dryer in summer…but not too dry. Available in pots at garden centers for transplanting; pure seed can be hard to find.

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Cutleaf Daisy

Scientific Name: Erigeron compositus

3-10”; full sun to part shade; dry, rocky to sandy soil; drought tolerant

Description: There are many kinds of daisies that grow in Colorado, and some can be hard to identify. This one is the exception. While all daisies have those distinctive buttons or clusters of tiny flowers in the center and strap-like or petal-like ray flowers spread all around in a circle, you can usually tell species apart by looking more carefully at the leaves. The cutleaf daisy is quite distinctive, mostly due to its finely divided leaves and the fact that it is one of few daisies that starts flowering in the spring. Most daisies flower only in the summer. This one is hard to miss with its flash of white on otherwise brown prairies and roadsides in the spring. It is called cutleaf daisy because of its unique finely divided leaves. Each leaf is divided into three narrow leaflets at the tip. Leaves are often divided in threes 2-3 times. The whole plant often forms a distinctive bunch with a ground-hugging tuft of crowded leaves at the base and several flower stems rising above them sporting white petal-like ray flowers, and yellow button-like disks in the center (the disk flowers). Rays (petals) can also be light blue or pink. Flowers are often tinged with purple when they first come out in spring, and before they fully open. These pigments help protect them before they are fully acclimated  to our often highly variable spring weather. If you look closely you can see the leaves have small, shiny glands on them and short, stiff hairs. These are adaptations for retaining water on the tough, dry sites where the plant often grows. Another daisy you might confuse with this one is the wandering daisy (Erigeron flagellaris), which may also flower in the spring. Like the cutleaf daisy, the wandering daisy also has small white to blue flowers, but its leaves are mostly long and narrow or rounded, not divided in threes at tip. Its growth habit is noticeably different too. Instead of being a small, compact clump, it can have long, taller flower stems and tends to spread out along the ground, hence the “wandering“ moniker. 

Height: Up to 10” tall, but typically 5” or less; grows in compact clumps.

Spread/Spacing: 4-6″; plant 6″ apart.

Soil Tolerances:  Prefers dry, rocky to sandy, well-drained soil. Can tolerate slightly alkaline soils.

Soil Moisture: Dry. Good waterwise plant.

Bloom: White to blue or with a purplish cast. Look for it from mid-April and May all the way through summer.

Value to Pollinators: Great pollinator host, especially for a wide variety of native bees as well as honeybees and butterflies. 

Deer & Rabbit Resistance: Resistant

Where they like to grow: Open rocky areas, grassy areas, alpine meadows, shrublands, and sometimes even along roadsides. 5,000’ to alpine. Common in mountains throughout the West.

Cultivation Notes: Can benefit from partial shade in high-heat areas. Tolerant of slightly alkaline soils. Needs well-drained rocky or sandy soils. Can propagate by division, or by cuttings, or seed. Perennial, dying back each winter and sending up new growth each spring.

Photo Credit: Paul Alaback

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Delicious Raspberry; Boulder Raspberry

Scientific Name: Rubus deliciosus; also known as Oreobatus deliciosus

Perennial; 3-5’; full sun, part shade; clay, loam, or sandy soil; drought tolerant

Description: Delicious raspberry (also frequently called boulder raspberry) is a mid-sized shrub native to Colorado and parts of New Mexico, Oklahoma and Wyoming. It prefers rocky areas and is often found growing near streams. In spring and summer, its fragrant, showy white flowers make it a beautiful addition to the landscape. Flowers are up to 3” wide with 5 petals and numerous stamens. Arching stems have a sprawling habit and older plants develop shredded bark. Leaves are large and bright green and are generally three-lobed. Unlike most other raspberry species, its stems do not have thorns. It may be hard to distinguish in the wild from thimbleberry, Rubus parviflorus, which has similar flowers and leaves. However, thimbleberry flowers are smaller and leaves are hairy on both upper and lower surfaces. (You may find nurseries selling both Rubus deliciosus and Rubus parviflorus as “thimbleberry.”) 

Delicious (or boulder) raspberry is a member of the bramble family. Its species name, deliciosus, is a bit of a misnomer. Unlike other raspberries, its berries are actually small, dry, and contain lots of seeds. Although they are not very appealing to humans, they are loved by birds and small mammals. This raspberry is a hardy native of northern Colorado and it grows well in both xeric and watered gardens. Good companion plants are artemisia species, yarrow, lavender, and other feathery grey plants. With its beautiful white flowers and large green leaves, boulder raspberry would make a lovely backdrop in a rock garden with boulders that resemble its native habitat. It also is a good choice for a specimen plant (to create a focal point) in more formal native gardens.

Height: 3 – 5’

Spread/Spacing: 5’ spread, 5 – 6’ spacing

Exposure: full sun to part shade; will not grow well in full shade

Soil Tolerances: clay, loam or sandy soil

Soil Moisture: dry to moist, well drained

Water: low to medium; good drought tolerance

Bloom: May - July; bright white with yellow center

Pollinator value: Pollinated by bees. Berries are food for birds.

Deer & Rabbit Resistance:  Unattractive to browsers, though deer have been reported to eat the berries.

Where they like to grow: Rocky areas, along streams, cracks in boulders.

Cultivation Notes: Plants are best started from nursery stock. They should be watered well until established, followed by occasional deep watering. Pruning out 1/3 of the older canes each year is recommended for specimen plants.

Photo Credit: Hilary Thomson (header); Jane Thomson (footer)

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Purple Prairie Clover

Scientific Name: Dalea purpurea

12-24″; full sun; loam, clay, gravelly, or sandy soil; drought tolerant

Description: This is a striking prairie wildflower with fine-textured leaves and show-stopping cylindrical, bright (neon-like) orchid-purple flower spikes on stiff stalks. Flower spikes are 1-2” long. Blooming begins at the bottom of the spike, progressing upward and filling out the cylinder over a flowering period that lasts 4-6 weeks. With a tough, thick taproot that can penetrate soil to a depth of 6 feet (!), it tolerates a wide variety of soil types, including clay. Young plants’ top-growth may be slow as energy is focused on developing the taproot. Because seeds are enjoyed by songbirds, spent flowers should not be deadheaded. Perennial.

Height: 12-24”

Spread/Spacing: 12″/12-18”

Exposure: full sun

Soil Tolerances: well-drained; adapts to loam, sandy, clay, gravelly, or alkaline soils

Soil Moisture: dry, medium

Water: low; excellent drought tolerance

Bloom: June-August, bright orchid-purple

Pollinator value: nectar and pollen for bees, butterflies; seeds for birds

Deer & Rabbit Resistance: moderately resistant; sometimes browsed by herbivores

Where they like to grow: Prairies, rock gardens, gravel, sand hills and dunes; In the picture above, purple prairie clover (foreground) in a naturally occurring community with orange/yellow blanketflower (Gaillardia aristata) in mid-ground, yellow flowerheads of Navajo-tea greenthread (Thelesperma megapotamicum) further back, and the wispy tan seed heads of needle-and-thread grass (Hesperostipa comata) in background.

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Smooth Blue Aster

Scientific Name: Symphyotrichum laeve 

1-3 feet; full sun or part shade; loam, clay, or sandy soil; drought tolerant

Description: Smooth blue aster is a North American native found in a wide variety of habitats, both moist and dry, across much of the United States, including Colorado. In our area, you might find it in some light shade near aspen trees or growing among needle-and-thread grass (Hesperostipa comata), blue grama (Bouteloua gracilis), and Western wheatgrass (Pascopyrum smithii) in an open mixed prairie. Its flowers, bracts, and leaves are usually hairless, but may be covered in whitish bloom (a film or waxy powder). Flowers are slightly less than an inch across and form broad, open clusters typically containing 10 to 20 heads branching out from stout main stems. (Plants normally have many more flowers than that pictured above. The specimen pictured was cut back for transplanting into the demonstration gardens.) The involucres are cylindrical or bell-shaped and lined by several series of small, non-overlapping phyllaries, often with dark tip, and not glandular (nor sticky). The purple-lavender ray florets (outer petals) usually number from 13 to 23, while the yellowish disc florets that make up the “button” center number 19 to 33. Leaves are alternate, thick and fleshy, 8-18 cm long, and range in shape from lance- to egg-shaped. Lower leaves have winged stalks, which are often withered. The upper leaves are smaller, stalkless, and often grasping the stem.

Plants develop an underground stem (caudex) and spread by rhizomes. These sub-surface structures are tough and fleshy enough to sprout after plant tops are killed by wildfires, browsed by deer, or otherwise damaged.

This plant will tolerate light shade, but not full shade. It is a late-season bloomer and the lovely blue-purple color of its showy, abundant flowers makes for welcome variety when it seems like everything else in the yard is only offering yellows and tans. The flowers attract butterflies and the plant blends well with mixed grasses and other wildflowers, making this plant a good choice for native wildflower and pollinator-focused gardens, or for re-vegetating meadows. 

Height: 1 – 3 feet

Spread/Spacing: 12-24”/ plant 18” apart

Exposure: Full to part-sun; won’t tolerate deep shade.

Soil Tolerances: Adaptable to a wide variety of soil types: chalk, clay, loam, or sandy soil. Medium CaCO3 tolerance. 

Soil Moisture: Dry

Water: Medium water use; may need supplemental water during long dry spells.

Bloom: July - October; Pale blue or purple with yellow center. Long, later-season bloom period.  

Value to Pollinators: Attracts butterflies and is the larval host for the Pearl Crescent butterfly (Phyciodes tharos).

Deer & Rabbit Resistance: Will likely be nibbled, but will likely survive to bloom again. Once established, plants can withstand grazing, as long as only stem tips are removed. Grazing often results in more vigorous growth. Some (not all) reports say deer and rabbits find the leaves unpalatable and will leave this plant alone. 

Where they like to grow: Open woods; dry to mesic prairies.

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Prairie Spiderwort; Western Spiderwort

Scientific Name: Tradescantia occidentalis

Perennial; 12-24”; full sun or part shade; any well-drained soil; drought tolerant

Description: Prairie spiderwort is an attractive, long-blooming perennial that, as its name suggests, is native to prairies, plains, and other open, sunny sites on the drier side. Plants may have pale lavender-blue, deep blue-purple, or magenta three-petaled blooms with six purple stamens flashing high-contrast, bright yellow anthers (the pollen-covered bits). Each flower lasts only a day, but clusters of buds keep the colorful show going from May to July. Foliage is somewhat sparse, long, slender, pointed, and a pretty bluish green. The plant generally has an upright, clumping habit, but stems may flop or lie prostate as the growing season progresses. Fallen stems can be propped up, staked, or cut back to keep things tidy. This plant is commonly found in dry and moderately moist sites, and is well adapted to any kind of soil as long as it drains well and does not stay wet for long periods. Prolonged wet leads to disease and root rot with this plant. Spiderwort stands up to intense heat and has good drought tolerance. A solitary plant won’t produce any seed, but when there are two or more specimens present, this species self-sows well. This is usually a bonus and not a problem in average, dry, low-fertility northern Colorado soils, but in more fertile soils the plant could have an aggressive habit. Prairie spiderwort belongs to a group of plants that can announce the presence of radiation in their environment. Under normal conditions, the hairs on the stamen of this plant are bluish purple, but they turn pink when exposed to ionizing radiation. Admirers of this widespread plant often lament its rather off-putting common name, but the unfortunate name is just an accident of referring to its features: “Wort” comes from the old English “wyrt,” which was used to refer to plants, herbs, or roots that were edible or medicinal. It so happens that the leaves, stems, seeds, and flowers of this plant have long been used as food and medicine. “Spider” does not refer to the arachnid itself, but the strands of its web. If you cut a spiderwort stem, it will exude thin, sticky sap that can be stretched into strands that resemble those in spiderwebs. Other common names for this plant are “snotweed” and “cow slobber.” Now you know why. As for its scientific name, the genus Tradescantia is a nod to John Tradescant, who was a gardener for England’s King Charles I in the 1600s. The descriptor occidentalis means “western,” describing the native range of this plant as distinct from related species.

Height: 12-24”

Spread/Spacing: 10-12” spread; plant 12” apart

Exposure: Full sun, part shade

Soil Tolerances: Any well-drained soil: sandy, sandy loam, loam, clay loam, or clay.

Soil Moisture: Dry to medium; prefers moist.

Water: Low; good drought tolerance.

Bloom: May-July; various shades of purple (pale purple, deep blue-purple, magenta)

Value to Pollinators: Nectar and pollen for bees and butterflies. Considered an important plant for native bees.

Deer & Rabbit Resistance: Said to have good deer resistance, but many refute that claim. Rabbits and other mammals will eat this plant.

Where they like to grow: Dry prairies, meadows, plains, south-facing slopes, edges of woodlands, sand dune crests.

Photo credit: Madeline Maher