Erigeron acris (Bitter Fleabane)
|Also known as:||Blue Fleabane|
|Life cycle:||biennial, short-lived perennial|
|Habitat:||part shade, shade, sun; rocky or sandy soil; cliff ledges, talus slopes, boreal forest, river banks, alpine meadows|
|Bloom season:||July - August|
|Plant height:||8 to 30 inches|
|Wetland Indicator Status:||GP: FAC MW: none NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Loose cluster of several to many stalked flower heads at the top of the stem. Flowers have numerous, erect to ascending, thread-like rays (petals) that average about ¼ inch (2 to 4.5 mm) long. Color is nearly white to pink to purplish. In the center are tiny yellow disk flowers.
Surrounding a flower head are several layers of bracts (phyllaries) that are linear, tapering to a pointed tip, variable in length, and sparsely to moderately covered in spreading hairs mixed with minute glandular hairs; the entire structure (involucre) is up to about ½ inch (5 to 12 mm) long. Flower stalks are sparsely hairy and often curved.
Leaves and stems:
Leaves are both basal and alternate on the stem, basal and lower leaves mostly narrowly spatulate, widest above the middle (oblanceolate), 3 to 6 inches (to 15 cm) long, to ~½ inch (14 mm) wide, rounded to blunt at tip, tapering to a short stalk. Edges are mostly toothless, sometimes with a few obscure teeth; surfaces are smooth to sparsely hairy, especially along the edges and major veins. Leaves become smaller, more lance to narrowly egg-shaped and stalkless as they ascend the stem.
Fruit is a medium to dark brown seed with a tuft of dull white to light brown hairs to carry it off in the wind. The hairs elongate as seed matures, eventually becoming about twice as long as the involucre.
Bitter Fleabane, known in some references as Erigeron acer, is a circumboreal species found across northern Asia, Europe and North America, its range dipping into the US lower 48 in northern New England, around Lake Superior, the Pacific Northwest, and throughout the Rocky Mountains. Habitats across its range include alpine meadows, boreal forest clearings and margins, and rocky river banks as well as disturbed soils such as gravel pits and roadsides. In Minnesota it is more particular in its habitats of rocky river banks near Lake Superior, talus slopes, and cliff crevices and ledges within our northern forests. According to the DNR, it was first discovered in 1929 but none of the early populations have been relocated. Erigeron acris was listed as a Special Concern species in 1996 but elevated to Endangered after biological surveys determined its true rarity in the state.
It is distinguished from other Fleabanes by the flowers with very short, erect to ascending, usually pinkish rays, and seeds with elongating hairs. The flowers may more closely resemble those of the weedy Horseweed (Conyza canadensis/Erigeron canadensis) but are larger, less numerous and more pink. Leaf shape, attachment (clasping or not) and distribution along the stem are additional differences between all these. Vegetative or fruiting plants might be confused with invasive Hawkweeds, which are widespread in the Arrowhead region of the state but tend to have longer hairs on leaves and stems and usually black hairs on the involucre and/or upper stem.
There are multiple vars (or subspecies, depending on reference) of Erigeron acris, but these are not well documented and the taxonomy is not consistent across references so distinguishing characteristics are not well understood (by us, at least), but the degree of hairiness seems to be a factor; var. kamtschaticus is recognized as present in Minnesota. Lastly, we observed that both we and the DNR have images of nodding seed heads, but this is not a characteristic noted in any reference. Coincidence?
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Photos by K. Chayka and John Thayer taken in Cook County.
Have you seen this plant in Minnesota, or have any other comments about it?