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Cirsium, Genus, altissimum, Species,

Genus & species

tall thistle

Asteraceae Central and eastern North America

Attracts Pollinators Attracts Butterflies Deer Resistant

SunFull Sun – Part Shade

WaterMedium

Overview

Cirsium altissimum is a tall biennial or short-lived perennial in the aster family (Asteraceae), growing 3-10 feet (0.9-3 m) tall on a single stout, grooved stem that branches near the top. In contrast to many thistles, its lance-shaped leaves are often unlobed or only shallowly lobed, 4-12 inches (10-30 cm) long, green above and densely white-woolly beneath, with weakly spiny margins. The flower heads are pink to rose-purple, 1-2 inches (2.5-5 cm) across, with a brush of slender disk florets above a vase-shaped base of spine-tipped bracts, borne singly at the branch tips. In the first year the plant forms a basal rosette, then bolts and flowers in its second year before dying. Blooming from late summer into fall, the heads draw heavy visits from bees and butterflies, and the seeds, carried on tawny down, feed goldfinches and other birds. One limitation in the garden is its height and biennial habit, which mean it reseeds and shifts position from year to year.

Native Range

Cirsium altissimum is native to central and eastern North America, ranging across the eastern and central United States into southern Canada. It grows in moist prairies, woodland edges, thickets, fencerows, and disturbed open ground.

Suggested Uses

This species is used in native pollinator gardens, prairie restorations, and meadow plantings where its late flowers support bees and butterflies. The seeds feed goldfinches and other seed-eating birds. Its height suits the back of borders and naturalized plantings.

How to Identify

Identification rests on a tall, single-stemmed thistle with lance-shaped leaves that are often unlobed and strongly white-woolly on their undersides, a contrast with the deeply cut leaves of many thistles. The pink to rose-purple heads, 1-2 inches (2.5-5 cm) wide, sit singly at branch tips above vase-shaped, spine-tipped bracts. The pale leaf undersides and great height help separate it from related native and weedy thistles.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread1' - 2'

Colors

Flower Colors

Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Flowers: August–October

Summer Fall

Flowering occurs from late summer into fall, mainly August through October. The pink-purple heads open over several weeks at the branch tips. Seed topped with tawny down ripens soon after and disperses on the wind.

Detailed Descriptions

Flower Description

pink to rose-purple

Foliage Description

green above, white-woolly beneath

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-12 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

Soil Requirements

pH Range5.5 - 7.5 (Acidic to alkaline)

3579

Soil Types

loam clay

Drainageaverage

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Cirsium altissimum grows in full sun to light shade in moist, fertile soils ranging from loam to clay, and tolerates a range of conditions in open ground. As a biennial it forms a rosette the first year and flowers the second, then dies after setting seed. It establishes readily from seed and reseeds on its own where soil is disturbed. No fertilizer or irrigation is needed in the rich sites it favors. Because it is a native thistle rather than an aggressive invasive, it is grown in pollinator and prairie plantings, though it can spread by seed. Removing seed heads before they ripen limits self-sowing where that is a concern.

Pruning

Pruning is limited to cutting back spent flowering stems. Removing seed heads before the down releases curbs reseeding, while leaving some allows birds to feed and the plant to renew itself. Stems die after flowering and can be cleared at the end of the season.