Doellingeria umbellata aka Umbellate Aster

Doellingeria umbellata is a perennial in the daisy family, Asteraceae. Its common names include parasol whitetop and flat-topped white aster. The older name Aster umbellatus refers to this species. Its native range spans eastern Canada and the north-central and eastern United States. It grows in moist fields, thickets, and along swamp edges. This wildflower loses its leaves for winter.

Garden plants reach 3.3–4.9 feet [1–1.5 metres] tall. Clumps spread 1.6–3.3 feet [0.5–1 metre] wide. Strong, upright stems give the plant a narrow, erect form. The smooth, round stems range from reddish to greenish yellow. Simple green leaves grow in an alternate pattern along them. Leaves are lance-shaped or oval, with tips that taper. Most measure 0.25–0.5 feet [0.08–0.15 metres] long. Their edges lack teeth but bear small fringe hairs. Lower leaves are small and scale-like.

Flowers appear from July through October in broad, flat clusters. Each small head has white rays around yellow disc flowers. The rays can show purple tints and bend down or back. These flower heads give the plant its flat-topped look. Silvery seedheads with soft tufts follow in autumn. The small, dry fruits are achenes with sparse hairs. Wind carries them away from the parent plant.

Grow this aster in sun or part shade. It prefers moist soil and can cope with occasional wet spells. Moderately fertile soil with good drainage suits garden plants. Sandy loam is a preferred soil, though RHS lists other types. These include clay, chalk, loam, and sand across different pH levels. RHS rates it H6 for cold hardiness. NC State lists USDA zones 3–9; Chicago lists zones 4–8. Plants reach their full size within two to five years. Divide clumps to raise more plants. Cut old growth back in late autumn or early spring.

Use it in borders, meadows, rain gardens, or near ponds. It also suits prairie-style planting and provides cut flowers. Planting in groups shows off the broad flower clusters. Flowers draw butterflies and other pollinators to the garden. Pearly crescent and Harris checkerspot larvae use it as a host. Seeds and underground rhizomes help it spread into nearby ground. NC State rates its upkeep as low. RHS reports few disease problems, but several pests may attack. Watch for slugs, snails, aphids, and leaf or bud eelworms.