Home » Plants » Eupatorium altissimum

Tall Thoroughwort (Eupatorium altissimum L.)

Also known as tall boneset.

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Summary
Range
Similar Plants
Habitat
Life Cycle
Fauna
Uses
Links
Photos

Photo © Peter Chen 2.0, CC BY 4.0.

↑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

Legend	Color
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.

Although this plant occurs somewhere in each of these regions, it may only occur in a small part of some or all of them.

We mark all new populations in the northeast as expanded. This species is only occasionally planted in landscaping; although escapes can originate from garden plants, it is a weedy species with wind-dispersed seeds, readily colonizing disturbed sites along roads, railroads, and industrial areas. Furthermore, its range expansion mirrors that of Eupatorium serotinum, which is even less-frequently planted.

↑Similar Plants

Late Boneset (Eupatorium serotinum)
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↑Habitat

Found in sunny, disturbed habitats, in mesic to moderately dry conditions. 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 reproduce on harsh sites where it cannot easily 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.

We could not find material establishing the seed banking behavior of this species with much confidence. Although many species in this genus form a long-term seed bank, we could not find verification that this species does. It has been found in the seed bank of prairies, but only in small numbers which suggests that, in these habitats, establishment may be more likely from freshly-distributed seed.

We also could not find material on this species' lifespan.

↑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.