White-Heath Aster (Symphyotrichum pilosum)
Sunflower Family (Asteraceae)
Aster pilosus, awl-aster, Michaelmas daisy, nailrod, steelweed, subulate-bracted aster.
Origin and Distribution:
White heath aster is a common weed throughout the eastern half of the U.S. including all of Ohio. It grows in old fields, orchards, pastures, roadsides, waste places, and sometimes no-tillage agronomic fields. The species prefers to grow in the open on dry sandy or gravelly soils.
White heath aster is a perennial weed that can frequently be seen growing by the side of the road as a clump of upright stems with wand-like spreading branches. In late August, small white flowers cover the top half of the plant. The flowers, which are similar to those produced by other plants in the Sunflower Family, are actually head-like clusters made up of many individual flowers that may be different shapes and colors. In the case of white heath aster, there are yellow disk flowers in the center of each head surrounded by 16 to 35 white ray flowers. Reproduction is by seeds.
Fibrous roots originate at the base of a perennial, woody crown.
Seedlings and Shoots:
Young leaves are alternate (1 leaf per node) with a green upper surface, grayish lower surface, and hairs on the edges and leaf stalks (petioles).
Stems are erect, 1 to 4 feet tall, and either smooth or with long, soft hairs. Stems are much-branched, especially in the upper half of the plant. Several erect, branched stems often emerge from the same root crown forming a clump.
Leaves are usually hairy. Lower leaves are lance-shaped, leaves located mid-way up the stem are more linear and lack petioles, and uppermost leaves are small, narrow, pointed, and numerous.
Flowers are grouped into heads that are 1/2 to 3/4 inch wide and located at the ends of branched stems. In the center of each flower head are yellow disk flowers that are surrounded by 16 to 35 white ray flowers (typically thought of as the petals).
Fruits and Seeds:
Fruits are light to dark brown, cone-shaped, and have a tuft of silky hairs (pappus) attached to the top. Each fruit contains a single seed.
New England aster (Aster novae-angliae) is one of several other aster species that are similar in appearance and distribution to white heath aster. However, New England aster has purple flowers and its leaves are larger than those of white heath aster. Fleabanes (Erigeron spp.) have white flowers that look similar to white heath aster flowers. However, fleabanes are annuals that begin to flower about 3 months before white heath aster. Also, compared with those of white heath aster, the white ray flowers surrounding the centrally-located yellow disk flowers are more numerous and narrower.
Flowering begins in late summer and continues until autumn. White heath aster is easily controlled by cultivation.