Late boneset, or late-flowering thoroughwort, is a native wildflower with clusters of white, fuzzy-looking flowers. It’s one of nine similar-looking species of thoroughworts in Missouri.
Late boneset is a stout native perennial whose stems and leaves usually have short hairs.
The flowers are white and are in fairly flat clusters at the stem tips; the flowers look fuzzy because the flowerheads lack ray florets, and the styles (pistil tips) are long and protrude. In this species, each small flowerhead contains 9–15 florets.
Blooms August–October.
The leaves are mostly opposite, lance-shaped or ovate, often angled at the base, with short but definite leaf stalks, tapered to a sharply pointed tip, with sharp, often coarse teeth along the margins. The leaves have 3 main veins (sometimes 5), with the ones on the sides branching off from the middle vein at the base of the leaf blade.
Similar species: Nine species of Eupatorium have been recorded in Missouri. Leaf characteristics are usually the best way to distinguish among the species.
- In Missouri, tall thoroughwort (E. altissimum) is most similar to late boneset. It has narrower and hairier leaves; they are slender-lance-shaped and taper nearly to the plant stalk, with short hairs and dotted with glands, with less coarse teeth that occur only above the middle of the leaves. Also, tall thoroughwort’s flowerheads only contain 5 florets (not 9–15). Note that late boneset can be just as tall as tall thoroughwort, and both bloom August–October.
- White snakeroot (Ageratina altissima) looks somewhat similar and, like late boneset, is also quite weedy. Compared to late boneset, the involucre (series of bracts at the base of each flowerhead) of white snakeroot appears greenish, while those of late boneset appear rather grayish. Also, compared to late boneset, the leaves of white snakeroot are not as narrow or with narrowly angled bases. Bear this in mind, because white snakeroot is quite poisonous.
Learn more about Missouri’s thoroughworts, or bonesets, on their group page.
Height: can bloom at 16 inches to over 6 feet tall.
Scattered nearly statewide.
Habitat and Conservation
Occurs in upland prairies, margins of glades, savannas, openings of mesic to dry upland woodlands, bottomland forests, banks of streams and rivers, margins of ponds and lakes, and ledges and tops of bluffs; also in old fields, fallow fields, pastures, gardens, railroads, roadsides, and disturbed areas.
This is one of the weediest of Missouri's thoroughworts and grows in a wide variety of habitats, soil moisture levels, or soil types. It spreads aggressively by seeds in gardens.
Status
Native Missouri wildflower.
Human Connections
Not all Missouri wildflowers are beloved by gardeners: this species spreads aggressively by seeds and can be hard to control. But where you can allow it to spread, or where it grows in natural settings, it draws butterflies, beetles, bees, and other insects that feed the birds you appreciate.
Ecosystem Connections
Many types of insects drink nectar from the flowers, and plants like this, that bloom late in the season, are crucial for insects that mature at that time.
Because of the foliage's bitterness, mammals don't usually eat this plant. Thus it can become increasingly abundant in pastures as livestock selectively eat more palatable plants.
