Colorado Tansyaster in the Landscape
Stephen Love, University of Idaho
Scientfic Name: Machaeranthera coloradoensis (syn. Aster coloradoensis, Xanthisma coloradoense)Common Name: Colorado Tansyaster
Description: Colorado tansyaster is a long-lived, mat-forming perennial with bright pink daisy flowers. Mature plants grow to a height of 5 inches and a spread of about 1 foot. Plants develop numerous stems and have toothed, grayish-green leaves. Flowers develop on short stems and have the appearance of floating at the top of the foliage. Flower heads form pink daisies with numerous ray flowers and yellow disk flowers in the center. Bloom period is long, often from May until October. Plants are herbaceous, each winter dying back to an above-ground crown and resprouting each spring. Colorado tansyaster is a very attractive, cushion plant that can be used to add color to all types of water-conserving beds and borders. This species is very effective when positioned in front of larger plants.
Native Habitat: Machaeranthera coloradoensis inhabits sparse grasslands or other open, bare sites on gravely limestone or sandstone derived soils. Native sites range from foothills to alpine tundra within an elevation range of 7,500 to 13,000 feet. The species is native to southern Wyoming and south-central Colorado.
Cultural Requirement
Soil: Colorado tansyaster tolerates a wide range of soil types, so long as the site is well-drained. Rarely requires application of supplemental soil nutrients.
Moisture Tolerance: This species thrives under dry to moderately dry conditions. May require a few mid-summer applications of supplemental water in areas with less than 10 inches of annual precipitation.
Sun/Shade/Preference: Requires full sun for best bloom expression.
Transplanting: Grows well in pot culture and transplants well from pot to pot and from pot to garden.
Propagation: Best grown from seeds. Seeds require no stratification or other pretreatment and consistently germinate at relatively high rates. Young seedlings grow at a moderately slow rate but, given enough time, can be encouraged to bloom in the pot. Plants typically bloom the first year in the garden. Pots up to 1-gallon size are appropriate for production of Colorado tansyaster.
Maintenance (pruning, fertilization, deadheading, division, irrigation, etc): Colorado tansyaster is a relatively carefree species. Deadheading is not essential and only minimal spring cleanup is necessary. Supplemental irrigation is recommended in the driest regions of the Intermountain West. Fertilizer is required only if plants show poor vigor.
Insect, disease, or other problems: Colorado tansyaster is usually pest- and disease-free.
Landscape Value
Use in the Landscape: Large flowers with bright pink color and long bloom period make Colorado tansyaster a valuable addition to any water-conserving landscape. This species can be used to create points of color as mass plantings or planted individually. Short stature means the most effective use of this plant is in small beds or in front of larger plants at the edges of larger beds and borders.
Weediness/Invasive Potential: Colorado tansyaster is not weedy from seed nor does it spread from rhizomes.
Foliage: Plants of Colorado tansyaster produce numerous short, branching stems that are at least partially decumbent. This growth habit results in the formation of broad, flat-topped mats. Leaves are dark grayish green, have toothed edges, and are covered with soft hairs.
Flower: Shape of the flower heads is typical of plants in the daisy family with a row of ray flowers around the outside edge and a button of yellow disk flowers in the center. Ray flowers are light to dark pink.
Timing: June-August.
Fruit: Each flower head produces several fruits consisting of hairless achenes (seeds).
Form: Loose mats.
Texture: Moderately coarse.
Ultimate Size: Up to 5 inches tall and about 1 foot across.
Rate of Growth: Colorado tansyaster grows slow as young seedlings but at a moderate pace once in the garden. Plants typically bloom during their first season in the garden.
Suggested Plant Partners: Surround Colorado tansyaster with small-statured ornamental grass species and color complimentary perennials, such as Idaho fescue (Festuca idahoensis), big bluegrass (Poa secunda), blue grama (Bouteloua gracilis), Hall’s penstemon (Penstemon hallii), Cusick’s hyssop (Agastache cusickii), oval-leaf buckwheat (Eriogonum ovalifolium), White Mountain buckwheat (Eriogonum gracilipes, featherleaf fleabane (Erigeron pinnatisectus), andtufted evening primrose (Oenothera caespitosa).
Availability: Rarely available for local sale as potted plants from native plant nurseries. Seed can occasionally be purchased from native plant seed suppliers.
Cultivars: No cultivars available.
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