Comprehensive DescriptionRead full entry
DescriptionThis perennial plant is about 1½–3' tall, branching occasionally. The light green to tan stems are terete and hairless (or nearly so). The opposite leaves are up to 5" long and 3½" across, becoming smaller as they ascend the stems. The lower leaves are cordate to cordate-ovate, while the upper leaves are broadly lanceolate to lanceolate. All of the leaves are largely hairless and strongly serrated-crenate along their margins; they are medium to dark green on their upper surfaces and light green on their lower surfaces. There are 3 prominent veins on the upper surface of each leaf (particularly the lower ones), while the lower surface has an elevated network of veins. The rather long petioles are ½–2½" in length. The upper stems terminate in compound corymbs or flat-headed panicles of flowerheads that span 2-6" across. The branches of this inflorescence are light green and glabrous (or nearly so). Each flowerhead is about ½" across and contains 10-30 disk florets that have brilliant white corollas and styles. There are no ray florets. Each disk floret is about 3-5 mm. across when it is fully open, consisting of a small tubular corolla with 5 lobes that are spreading and pointed and a divided style that is strongly exerted from the corolla. At the base of each flowerhead, there is a single series of linear floral bracts that are light green and non-overlapping. The blooming period occurs from late summer through the fall, lasting about 2 months for a colony of plants. This is one of the last wildflowers to bloom during the fall. The flowers are often fragrant. During autumn, each disk floret in a flowerhead is replaced by an achene with a small tuft of white hairs. These achenes are 2-3 mm. long, narrowly oblongoid in shape, 5-ribbed, and black; they are distributed by the wind. The root system consists of spreading rhizomes and shallow fibrous roots. This plant can spread vegetatively by means of its rhizomes, or it can reseed itself into new areas.