Plants of the Eloise Butler Wildflower Garden

Flat-topped Aster is a native erect perennial growing on stems that are 3 to 6 feet high, reddish color lower and green to reddish-green in and near the inflorescence. Stems may be smooth or slightly hairy.

Leaves are lance shaped, 4 to 6 times longer than wide, entire, stalkless on the uppers, short stalks on lower leaves, tapering at both ends. Leaves on the mid and upper part of the stem are more crowded than below and reduce in size toward the inflorescence. Leaves of this variety are densely hairy on the underside.

The floral array is a flat-topped branched cluster; the entire array is composed of a number of smaller open clusters (which are known as corymbiform arrays), each array on its own stalk, branching and sub-branching from the main stem. In a corymb the flower stalks are of different length so that the flowers form a flat-topped cluster. Stems and flower stalks within the array have fine hair.

Flowers: The small flowerheads (1/2 to 3/4 inch wide) have two types of florets: White ray florets of 2 to 10+ rays which are pistillate and fertile, surrounding a central disc of 5 to 26+ disc florets which are bisexual and fertile. Disc florets are tubular with five anthers appressed against the style. The 5 lobes of the disc corollas are light yellow with outward turned and reflexed lips. Unlike asters in the Symphyotrichum genus, these do not turn reddish-purple at maturity. The outer circumference of the flower heads have 3 to 4 series of phyllaries that are light green, linear, tips tapering to a point and somewhat overlapping. In this species, the midvein of the phyllary is not swollen. The phyllaries are of unequal length with faces covered with very short stiff hair.

Seeds: Fertile flowers produce a 4 to 6 ribbed dry cypsela covered with stiff short hairs, that has 4 series of bristles attached for wind dispersion. The outer bristles are linear and pointed, whitish, while the 3 inner series are white to tan with barbed tips. These 4 whorls of bristles are distinctive of the Doellingeria genus. Seeds require at least 60 days of cold stratification for germination.

Varieties: Two varieties are recognized: var. pubens, described here and var. umbellata where the underside of the leaves are sparsely hairy. Both are native to Minnesota, but the DNR county plant surveys do not distinguish between them.

Habitat: The plant does well in moist soil and full sun and is one of the earliest blooming asters in the Woodland Garden along the wetland trail. It also does well in the somewhat drier upland savanna habitat. It grows from a rhizomatous root system which can produce a short woody crown.

Names: Formerly classified as Aster umbellatus, Flat-topped Aster, like most other North American asters, has recently been reclassified by botanists into another genera. A large number went to Symphyotrichum but this one and two others are now in Doellingeria. These latter are, most generally speaking, the white flat-top asters. The genus name Doellingeria is an honorary for Ignatz Doellinger (1770-1841), German doctor, anatomist and physiologist, professor at Bamberg and then Munich. One of his students was Louis Agassiz. The species name, umbellata, refers to the umbrella-like flower heads. The variety pubens refers to the dense hair on the leaf underside. The author names for the plant classification are: "Mill." is for Philip Miller, Scottish botanist (1691-1771) who was chief gardener at the Chelsea Physic Garden and wrote "The Gardener's Dictionary". His work was updated by 'Nees' who is Christian Gottfried Daniel Nees von Esenbeck (1778-1858) German botanist who described around 7000 plant species, authored a number of monographs and was a Professor at Erlangen, Bonn and Breslau.

Comparison: Flat-topped Aster with a flat-topped umbrella like cluster of white flowers is not confused with any other in Minnesota. The two other similar species, D. infirma and D. sericocarpoides are found near the east and gulf coasts.