Northern Ontario Plant Database

Plant Description

Doellingeria umbellata (Mill.) Nees

En: flattop white aster, tall flattop white aster, parasol whitetop
Fr: aster à ombelles

Asteraceae (Daisy Family)

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Synonym: Aster umbellatus Mill.

General: An erect perennial, 0.3—2 m tall, spreading by rhizomes. Stems are single or few-branched below the flowering head, usually green to reddish, and nearly smooth (glabrous) to somewhat hairy.

Leaves: Basal leaves are absent. Stem leaves are alternate, simple, and sessile. Blades are lanceolate to elliptic, 6—15 cm long by 1.3—3.5 cm wide; mid-stem leaves are larger than upper leaves. Blades taper gradually to the narrow (attenuate) base and sharply-pointed (acuminate) apex, margins are entire and edged in fine hairs (margins ciliate). Leaf surfaces are nearly glabrous to densely hairy beneath. Of the 2 varieties in the Algoma area, var. pubens (A.Gray) Britton has broader leaves that are densely hairy beneath, while the typical variety, var. umbellata, found in southern Algoma only and throughout southern Ontario, has narrower leaves sparsely hairy on the lower surface, especially along the veins.

Flowers: All plants in the Aster Family have flowers arranged in inflorescences called heads, which are composed of few to many small flowers attached to a base covered with overlapping rows of bracts (phyllaries), collectively called an involucre. Flowers of flattop white aster are arranged in a terminal leafy-branched inflorescence (corymb), 7.5—30 cm across, composed of many small heads (20—100+), each 1.3—2 cm across. Each head has 4—15 white ray flowers, 5—10 mm long, surrounding a centre of 10—40 small yellow disc flowers. Involucres are 2.5—5 mm long and composed of 3—4 overlapping rows of lanceolate blunt-tipped phyllaries. In the central disc of flattop white aster heads, the anthers are very prominent and extend beyond the small disc flowers. Flowers bloom in late summer.

Fruit: Small achenes, 1.4—3.2 mm long, narrowly obovoid, lined with 4 vertical ribs. The achene surface bears short stiff hairs and is topped by 2 rows of whitish to pale brownish bristles (pappus bristles), which function in wind-dispersed.

Habitat and Range: Moist to somewhat moist soils in fields, clearings, rights-of-way, thickets, forest margins, and roadsides. Flattop white aster is a temperate North American species whose range extends from Newfoundland to Alberta. It is found throughout the Algoma District and most of Ontario. Doellingeria umbellata var. pubens has a Canadian range that extends from Quebec to Alberta, while the typical var. umbellata can be found from insular Newfoundland west to central Ontario.

Similar Species: There are several species of white-rayed asters in the Algoma, but each of these have much narrower leaves and smaller heads arranged along open spreading branches, rather than in a terminal, flat-topped cluster. Technical differences that separate Doellingeria from other asters (Symphyotrichum species) are based on the number or rows of pappus bristles circling the top of the small fruits. Flattop white aster fruits have a very short outer whorl of bristles and an inner whorl of longer bristles, about 3.5—6 mm long. Asters in the genus Symphyotrichum have a single row of pappus bristles.