Kate Manning, no rights reserved (CC0) · iNaturalist

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Silphium spp.

rosinweeds

Asteraceae Central and eastern North America

Attracts Pollinators Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun – Part Shade

WaterMedium · drought-tolerant

HardinessZones 3–9

Overview

Silphium spp. is a genus of about 12 to 20 species of tall, coarse perennials in the daisy family Asteraceae, native to the prairies, savannas, and open woods of central and eastern North America. Plants form clumps of stout, often rough-hairy stems 3 to 10 ft (0.9 to 3 m) tall that exude a sticky resin when cut, the source of the name rosinweed. The large leaves vary by species: S. perfoliatum, the cup plant, joins its opposite leaves around the stem to form cups that catch rainwater; S. laciniatum, the compass plant, holds its deeply cut leaves on a north-south plane; and S. terebinthinaceum, prairie dock, lifts huge basal leaves above bare stalks. Yellow, daisy-like flower heads 2 to 4 in (5 to 10 cm) across open through summer atop the branched stems. Deep taproots reach several feet down, making mature plants drought tolerant and long-lived but hard to transplant. Limitations include the large size, a tendency to self-seed and spread, and slow establishment in the first year or two from seed.

Native Range

Silphium spp. is native to North America, centered on the tallgrass prairies and oak savannas of the Midwest and the eastern United States, reaching into southern Canada and the Gulf states. Plants grow in prairies, meadows, roadside remnants, and open woodland on deep soils. Several species are now planted in restorations well beyond their original range.

Suggested Uses

Silphium spp. is planted in prairie and meadow restorations, rain gardens, and the back of large borders, and the cup plant is used at pond and stream edges. The tall stems and seed heads support pollinators and seed-eating birds in wildlife gardens. Plants are massed as a screen or backdrop in naturalistic schemes.

How to Identify

Identify Silphium spp. by its tall, stiff, resinous stems and large, rough leaves, paired with yellow, daisy-like flower heads in which both the ray and disc florets set seed. Cut stems and leaves give off a sticky, turpentine-scented resin. Species are told apart by leaf form: cupped and joined in S. perfoliatum, deeply lobed and vertical in S. laciniatum, and large and spade-shaped at the base in S. terebinthinaceum.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread1'6" - 4'

Colors

Flower Colors

yellow

Foliage Colors

green

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Silphium spp. blooms from midsummer into early autumn, with most species flowering from July through September over six to ten weeks. The branched stems open many yellow heads in succession. Bees and butterflies work the flowers, and goldfinches and other birds feed on the ripening seeds.

Detailed Descriptions

Foliage Description

green to grey-green

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 Range6.0 - 7.5(Neutral)

357912

Soil Types

loam clay sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

2-3 years to flowering, long-lived once established

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Silphium spp. grows in full sun in deep, fertile soil with a pH from about 6.0 to 7.5, and most species tolerate clay and seasonal moisture; the cup plant takes wet ground that other species avoid. Young plants need steady moisture, but the deep taproot makes established clumps drought tolerant and very long-standing. The genus is cold hardy across zones 3 to 9 and dies back to the crown each winter. Plants self-sow and form expanding clumps, so they suit large, naturalistic plantings rather than tight borders. Tall stems may lean in rich soil or shade and can be cut back early in the season to limit height.

Pruning

Silphium spp. is cut to the ground in late winter or early spring before new growth begins. Spent stems can be left standing through winter for birds and overwintering insects. Cutting the stems back by half in early summer reduces height and the chance of flopping.