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Tall Thoroughwort (Eupatorium altissimum)

Also known as tall boneset.

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Tall Thoroughwort

Summary

An upright perennial of dry, sunny, disturbed habitats, often on calcareous soils, native to the eastern to central US and expanding into the northeast.

Range - Expand

LegendColor
Native
Expanded
Native or Not Present
Native or Expanded
Expanded or Not Present
Native or Expanded or Not Present

This tentative map is based on our own research. It may have limited data on Canada and/or Mexico, and there is some subjectivity in our assignment of plants as introduced vs. expanded. Read more in this blog post.

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Late Boneset (Eupatorium serotinum)
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Habitat

Found in sunny habitats, in average to moderately dry conditions, especially on sites that have been recently disturbed. Natural habitats inclde dry prairies with soils including black soil, clay, and gravel, savannas, openings in upland woodlands, dry portions of lake banks, and limestone barrens. Also found in numerous anthropogenic habitats, including pastures and abandoned agricultural land, fence rows, vacant lots, railroads, and industrial areas.

Needs considerable direct sun, and found in full to partial sun, but able to compete favorably with ground-level vegetation due to its height. Requires more sun in the north of its range, whereas in the south of its range it is more likely on sites shaded from afternoon sun. Tolerates clay and gravelly soils, compacted soils, and areas with little soil due to rock or pavement, but usually absent from sandy soils. Often found in calcareous soils, and tolerates high soil pH.

We could not find information on this species' fire tolerance, but it occurs in habitats that burn regularly and is likely highly tolerant of fire. It probably benefits from the removal of competing vegetation brought by fire.

Life Cycle

This species is a clumping perennial.

Due to its preference for habitats that are drier and often lower in organic nutrients, this species is slightly slower to establish than other closely-related plants. Plants may take a few years to reach their full height; established plants form clumps with multiple stems, spreading by short rhizomes, usually at most a few inches per year.

In periods of drought, leaves will dry up, but plants may still flower, and are usually unaffected in the long-run, sometimes surviving the drought better than competing vegetation.

Plants flower in late summer to early fall. There are two separate populations of this species; one, found mostly in the Ozarks in Missouri and Arkansas, reproduces sexually and must be cross-pollinated. However, the majority of populations of this plant reproduce asexually, producing seeds through agamospermy. This adaptation has likely helped this species to rapidly colonize new areas starting with an isolated individual, and has allowed it to survive in areas where it cannot effectively attract pollinators.

Seed matures in fall, and is wind-distributed, and seeds exhibit cold dormancy, germinating in the following growing season. Seeds usually mature gradually, over a period of several weeks, with some seed beginning to be distributed while the plant is still in bloom. This species has been found in the seed bank of prairies, but only in small numbers. Given the high volume of seed production and the fact that it is wind-dispersed, it is likely that most seed germinates and long-term survival in the seed bank is low, and most colonization of this plant by seed occurs from wind-blown seeds.

Faunal Associations

In spite of the asexual reproduction of most populations of this plant, it still provides nectar, and attracts a wide range of pollinators, even to plants that do not produce any pollen. The flower tubes are easily accessible, and visited by long-tongued and short-tongued bees, wasps, flies, butterflies, skippers, beetles, and bugs.

Mammals usually avoid browsing this plant due to its bitter, toxic foliage.

Uses

This plant is occasionally used as a landscaping plant, and is probably under-utilized as such. It is valued for its drought tolerance, resistance to deer browsing, and the fact that it usually grows upright and supports its weight even without any supporting vegetation.

Eupatorium altissimum (Tall Boneset) | Illinois Wildflowers (About This Site)

Eupatorium altissimum (tall thoroughwort) | USDA PLANTS Database (About This Site)

Eupatorium altissimum | Go Botany (About This Site)

Eupatorium altissimum (Tall Thoroughwort) | Missouri Botanical Garden Plant Finder (About This Site)

Eupatorium altissimum | Biota of North America Project (BONAP) (About This Site)

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Photo © Alex Zorach, CC BY-SA 4.0.
Photo © pobrito, Public Domain.
Photo © Matt Schultz, Public Domain.
Photo © pobrito, Public Domain.
Photo © Lindsey G., CC BY 4.0.
Photo © Mathew Zappa, CC BY 4.0.
Photo © Daniel McClosky, CC BY 4.0.
Photo © Peter Chen 2.0, CC BY 4.0.