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Late Boneset (Eupatorium serotinum Michx.)

Also known as lateflowering thoroughwort.

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Late Boneset

Summary

A perennial of sunny, disturbed, average to wet areas, native to the southeastern to central US, 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.

This species has wind-dispersed seeds and thrives in disturbed habitats, including along roads and railroads. It is not widely planted in gardens. It is expanding its range, particularly in the northeast, but also expanding northward somewhat in the Midwest.

Similar Plants

thumbnail of White Snakeroot
White Snakeroot (Ageratina altissima)
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thumbnail of Tall Thoroughwort
Tall Thoroughwort (Eupatorium altissimum)
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Habitat

Found in a range of open to partly-sunny areas with moist conditions, especially areas that have been disturbed recently. Habitats include sunny opening in floodplains and swamps, moist black soil prairies, wet ditches along roadsides and railroads, and wet portions of abandoned fields or overgrazed pastures.

Prefers loamy soil rich in organic matter, but tolerates sandy soil on sufficiently moist sites, especially along streams.

This species often co-occurs with its close relatives. Relative to E. perfoliatum, late boneset is more tolerant of heat and drought and less tolerant of flooding, clay and compacted soils, and soil erosion. Relative to Ageratina altissima, late boneset is less shade tolerant. Relative to tall thoroughwort (Eupatorium altissimum), this species is more tolerant of low-calcium and acidic soils but less drought-tolerant.

Life Cycle

This species is a clump-forming perennial.

Seeds typically germinate in late spring to early summer, usually triggered by direct sunlight resulting from a small-scale soil disturbance. Seedlings develop a fibrous root system, and grow a single stem that almost never reaches its full height. Plants often do not flower in their first year; if they do, flower and seed production tends to be minimal.

Plants flower from late summer into early fall, with seeds maturing later in fall. Seeds are wind-distributed and are mostly blown away by winter, with the timing of distribution depending both on the site and timing of higher-wind weather events. Seeds may germinate as early as the first spring following distribution, but can also persist long-term in the seed bank. We could not find information about the exact longevity of seeds in the seed bank, but comparison to closely-related, ecologically-similar species suggests many seeds likely persist 5-10 years with smaller numbers persisting 10-20 years or longer.

On favorable sites, plants reproduce vegetatively at their base by short rhizomes, forming concentrated clumps with multiple stems. Rhizomes rarely travel far from the parent plant. Some plants do not reproduce vegetatively and only send up a single stem in their second year; overall this plant is more likely than other species of the Eupatorieae tribe to grow with a single-stem habit.

The lifespan of individual plants varies widely, and typically ranges from 4-11 years. Mortality can occur due to a variety of conditions, including shading from a canopy of overhead trees as a previously-disturbed site develops,prolonged flooding on a low-lying site, or drought. This plant usually tolerates herbivory and competes well with ground-level herbaceous plants and is normally only out-competed or harmed by insects or disease if site conditions are otherwise stressing it.

Faunal Associations

Supports a wide range of insects, mostly those that are supported broadly by plants of the Eupatorieae tribe. The nectar is highly accessible and supports a wide range of pollinators, including long- and short-tongued bees, wasps, flies, butterflies, skippers, and moths, and including insects of a broad range of sizes. Several moth larvae eat the foliage of this plant. The seeds are eaten by small birds.

Mammalian herbivores avoid this plant due to its toxicity.

Uses

Historically this plant was used medicinally. Unlike some of its relatives, this plant is less frequently used in landscaping. Its main use is in rain gardens and on other low, wet sites. Its use is limited by its large maximum height and tendency to flop over, as well as its tendency to wilt and look sickly in periods of drought, even if the plant itself remains healthy long-term. On favorable sites it has a tendency to dominate garden plantings. It is best planted together with supporting vegetation, on sites with consistent moisture.

This plant is frequently used in ecological restoration plantings and in drainage basins. It often thrives on the margins of drainage ponds and in basins.

In North America, there are around 30 other species in the Eupatorium genus, all but one of them native. There are even more species in the broader Eupatoriae tribe.

Eupatorium serotinum (Late Boneset) | Illinois Wildflowers (About This Site)

Eupatorium serotinum (Late Boneset) | USDA PLANTS Database (About This Site)

Eupatorium serotinum | Go Botany (About This Site)

Late Boneset | iNaturalist (About This Site)

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

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