Erigeron annuus is a herbaceous plant with alternate, simple leaves, and green, sparsely hairy stems, which can grow to between 30 and 150 centimeters in height. Leaves are numerous and large relative to other species of Erigeron, with lower leaves, especially basal leaves, coarsely toothed or cleft, a characteristic readily distinguishing this species from most other Erigeron. Upper leaves are sometimes toothed, but may have a few coarse teeth towards the outer tips. The flower heads are white with yellowcenters, with rays that are white to pale lavender, borne spring through fall depending on the individual plant. Ray floretsnumber 40 to 100.
Range
Erigeron annuus is native to North America, and is found in 43 of the 48 states within the contiguous United States. It is widespread in many of them, especially in the eastern part of its range, but occurs only in scattered locations in the western and southernmost parts of its range. It has been introduced to many other places, including Korea.
It often grows as an annual but can sometimes grow as a biennial. Erigeron annuus is a native pioneer species that often colonizes disturbed areas such as pastures, abandoned fields, vacant lots, roadsides, railways, and waste areas. In these habitats it competes, often successfully, with introduced invasive weeds.
Habitat preferences
Erigeron annuus grows well in full through partial sun, on sites with ample moisture. It is tolerant of a wide range of soil conditions, including gravel and clay. In hot, dry weather, lower leaves often yellow and wither.
Faunal associations
Flowers are pollinated by a variety of bees, including little carpenter bees, cuckoo bees, halictine bees, and masked bees; as well as flies, including syrphid flies, bee flies, tachinid flies, flesh flies, anthomyiid flies, and muscid flies. Wasps, small butterflies, and other insects also visit the flowers to a lesser degree, seeking nectar, as well as a few pollen-feeding beetles. Schinia lynx caterpillars feed on the flowers and seeds of annual fleabane and other fleabanes, and Lygus lineolaris sucks the plant juices. Some mammals eat the foliage, flowers and stems, including sheep, groundhogs, and rabbits.
