Eupatorium altissimum
tall boneset
Overview
Eupatorium altissimum is an upright herbaceous perennial reaching 3-6 feet (0.9-1.8 m) tall and 1-3 feet (30-90 cm) wide, forming clumps from a fibrous-rooted crown. The downy gray-green stems rise in dense stands and branch toward the top. Opposite leaves are lance-shaped, 2-4 inches (5-10 cm) long, with three prominent veins running from near the base and a few teeth above the middle. Flat-topped clusters of small white flower heads top the stems from August to October, each head holding about five tubular disk florets and no ray petals. The clusters draw many late-season pollinators before seed set. Dry seeds tipped with white bristles follow and disperse on the wind. The species grows in dry prairies, glades, old fields, and open woodland on rocky or clay soils, tolerating drought and poor ground. It spreads by seed and can self-sow heavily in open sites. Plants may flop in rich soil or shade without support. The foliage is bitter and generally avoided by browsing animals.
Native Range
Eupatorium altissimum is native to central and eastern North America, from the eastern Great Plains and Texas east to the Atlantic states and north into the Great Lakes region. It grows in dry prairies, limestone glades, old fields, fencerows, and open woods.Suggested Uses
Used in prairie and meadow plantings, native borders, and pollinator gardens on dry soils, spaced 18-24 inches (45-60 cm) apart. Suited to rocky or clay sites where many perennials struggle. The late flowers support migrating butterflies and other pollinators before frost.How to Identify
Appearance
Size & Dimensions
Height3' - 6'
Width/Spread1' - 3'
Reaches mature size in approximately 2 years
Bloom Information
Detailed Descriptions
Foliage Description
Gray-green, downyGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grow Eupatorium altissimum in full sun to part shade on dry to medium, well-drained soils, including clay, rocky, and limestone ground. It tolerates drought, heat, and poor fertility once established and accepts a pH from 6.0 to 7.8. Plants reach full height in two seasons and may lean in rich soil or shade, where support or a sheltered spot keeps them upright. Cutting the stems back by half in early summer lowers the mature height and reduces flopping. The species self-sows freely, so spent heads can be removed before seed drop to limit volunteers. Little fertilizer is needed.Pruning
Cutting stems back by one-third to one-half in late spring or early summer produces shorter, sturdier plants. Spent flower clusters are removed in fall to limit self-sowing, or left to feed birds. Old stems are cut to the ground in late winter.Pruning Schedule
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F
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late springwinter