Tall Thoroughwort (Tall Boneset)

Eupatorium altissimum

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Photo of a tall thoroughwort plant in bloom.
Tall thoroughwort has dull white flowers and distinctive opposite, slender, very short-stalked leaves with three noticeable veins.
Family

Asteraceae (daisies)

Description

A stout native perennial whose stems are hairy in the top half of the plant. Flowers clustered loosely at the tops of stems in narrow, flat-topped configurations; only 5 florets in each head, flowers dull white. Bracts beneath the flowerheads are broad and rounded. Blooms August–October. Leaves mostly opposite, widely spaced, to 5 inches long, strongly 3-nerved, very short-stemmed or sessile, slender lance-shaped and tapering nearly to the plant stalk, with short hairs and dotted with glands, with teeth above the middle of leaves only.

Similar species: There are 11 Eupatorium species in Missouri. The most common ones can usually be separated by flower color (white or gray versus pale pink or pale purple) and by a combination of leaf characteristics.

Size

Height: generally 3-4 feet, but often more than 6 feet.

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Photo of tall thoroughwort flowers closeup from side.
Tall Thoroughwort (Tall Boneset) Flowers
Tall thoroughwort has only 5 florets in each head, and the florets are dull white.

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Photo of tall thoroughwort stem with leaves.
Tall Thoroughwort (Tall Boneset) Stem and Leaves
Tall thoroughwort can be more than 6 feet tall, which explains the name.

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Photo of tall thoroughwort leaves.
Tall Thoroughwort (Tall Boneset) Leaves
The leaves of tall thoroughwort are helpful for identifying it.

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Photo of tall thoroughwort multiple flower clusters.
Tall Thoroughwort (Tall Boneset) Flower Clusters
The flowers of tall thoroughwort are clustered loosely at the tops of stems in narrow, flat-topped configurations.

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Photo of tall thoroughwort flowers, closeup.
Tall Thoroughwort (Tall Boneset) Flowers
Tall thoroughwort blooms August–October, and the same dates apply for fruiting time.
Habitat and conservation

Occurs in prairies, fields, glades, open woods, banks of streams and rivers, ledges and tops of bluffs, ditches, quarries, roadsides, and other open, disturbed, or waste places.

image of Tall Thoroughwort Tall Boneset distribution map
Distribution in Missouri

Statewide but uncommon in Southeast Lowlands.

Human connections

Folk medicine has given this plant its enduring name of “boneset.” The first pharmacists and doctors were botanists, since humans have for millennia recognized the medicinal properties of plants. People are still researching the chemicals in plants to find cures for human illness.

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.