This native perennial is usually found in dense colonies near water or where the soil is moist (C). These large plants, to 6 feet and taller, have hairy, purplish stems and branches. The stalked leaves are lance-shaped and up to 6 inches long. The numerous white flower heads form flat clusters (corymbs) atop stems and branches (A). Each cluster consists of several smaller groups of up to 15 tiny white disk flowers with 5 petal-like lobes and long protruding styles (B). Seeds have a tuft of attached fluffy white hairs which aid their dispersal by the wind.
Found near water and other moist ground, flowering from August through October. It is common close to water on trails near the Great Marsh and Hidden Lake at Fontenelle Forest and uncommon on the floodplain at Neale Woods.
Other common names include Boneset and Late-Flowering Thoroughwort.
Eupatorium serotinum is just one of several “look-alikes” that bloom in late summer and fall. It most nearly resembles Tall Boneset (Eupatorium altissimum) which is found in drier, upland habitats, is not likely to be found in large colonies, does not have purplish stems, has leaves with no stalks and usually has no more than 5 disk florets per group. False Boneset (Brickellia eupatorioides), also a plant of drier uplands is a smaller plant with alternate leaves having only 1 prominent vein; Late Boneset has 3. Common Boneset (Eupatorium perfoliatum) occupies similar moist habitats, but its leaves are fused at the base totally enveloping the stem. A very common woodland species, White Snakeroot (Ageratina altissima) has much broader, coarsely toothed leaves.
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