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Kate Manning, no rights reserved (CC0) · iNaturalist

Silphium, Genus, perfoliatum, Species,

Genus & species

cup plant

Asteraceae Central and eastern North America

Attracts Pollinators Attracts Butterflies

SunFull Sun – Part Shade

WaterHigh

HardinessZones 3–9

Overview

Cup plant is a tall, coarse native perennial in the aster family, growing 4-8 feet (1.2-2.4 m) tall and 1-3 feet (30-90 cm) wide on stout, square stems. Its common name comes from the large, opposite leaves, which are joined at the base around the stem to form a shallow cup that catches and holds rainwater. The rough, triangular leaves can reach 8-14 inches (20-35 cm) long lower on the plant. From midsummer into early autumn branched stem tips carry yellow, sunflower-like flower heads 2-3 inches (5-8 cm) across, with bright ray florets around a paler central disk. Silphium perfoliatum spreads by thick rhizomes and self-seeding to form broad, long-lived clumps, which can crowd smaller plants and overrun a small bed. It grows tall and may lean or need support in rich soil or wind, the main trade-off for its height and bloom. The water-holding leaf cups draw birds and insects, and goldfinches feed on the ripe seeds. It prefers moist ground and tolerates heavy clay and seasonal wetness.

Native Range

Native to central and eastern North America, from Ontario and the Great Lakes south to the Gulf states and west to the Great Plains. Silphium perfoliatum grows in moist prairies, stream banks, low woods, and wet meadows.

Suggested Uses

Grown in rain gardens, native and prairie plantings, pond and stream edges, and the back of large borders where its height and yellow bloom carry. It draws pollinators, birds, and beneficial insects in wildlife gardens. Its spread and size suit large, open spaces rather than small beds.

How to Identify

Recognized by tall, square stems and large, rough, opposite leaves whose bases fuse around the stem into a rainwater-holding cup. Yellow sunflower-like heads 2-3 inches (5-8 cm) across top branched stems in summer. The cupped, perfoliate leaves separate it from sunflowers and from other Silphium species with separate or lobed leaves.

Appearance

Size & Dimensions

Height4' - 8'

Width/Spread1' - 3'

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~8 weeks

Flowers: July–September

Summer Fall

Blooms from midsummer to early autumn, often July through September, over six to eight weeks. The yellow heads open in succession at the branched stem tips, with the central buds following the first. Seed ripens through late summer and draws finches and other seed-eating birds.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

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

Soil Requirements

pH Range5.5 - 7.5 (Acidic to alkaline)

3579

Soil Types

clay loam silt

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Grows in full sun to part shade in moist to wet, fertile soil with a pH from 5.5 to 7.5, and tolerates heavy clay. It establishes a deep root system and is slow to settle the first year, then grows tall and spreads steadily by rhizomes. Steady moisture supports the fullest growth, though established plants tolerate short dry spells. It needs no feeding in average ground, and very rich soil produces tall, leaning stems. Clumps can be divided in spring to control spread and renew the center as it ages. The rigid stems usually stand on their own but may need support in exposed, windy sites.

Pruning

Stems can be cut back by a third in early summer to lower the eventual height and reduce flopping. Spent flower heads are left to feed birds or removed to limit self-seeding. Old stalks are cut to the ground in late autumn or left standing for winter wildlife.

Toxicity

Non-toxic

Related Silphium species