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Tridens spp.

Purpletop

Poaceae Americas

Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun – Part Shade

WaterLow · drought-tolerant

HardinessZones 5–9

Overview

Tridens spp. is a genus of about fifteen warm-season grasses in the family Poaceae, native to the Americas and most strongly represented in the United States and Mexico. Most are tufted perennial bunchgrasses forming clumps of narrow leaves with airy flowering panicles held well above the foliage. The purpletop, T. flavus, is the widely seen species, a clump-former 2-5 feet (0.6-1.5 m) tall whose open, branching seed head flushes purple to bronze in late summer and is coated with a sticky, greasy film that gives the alternative name greasegrass. The genus grows in prairies, old fields, open woods, and roadsides, often on poor or disturbed ground. The narrow leaves turn yellow to bronze in autumn before the clump goes dormant for winter. Plants are wind-pollinated, with the colour and movement of the panicle being the main feature rather than any showy flower. Spread is by seed and slowly expanding clumps, and the grasses tolerate heat, drought, and poor soil once established, though they can self-seed into open ground. The genus name refers to the three small teeth at the tip of each flower scale.

Native Range

Native to the Americas, with most species in the central and eastern United States and Mexico and a few extending into South America, in prairies, open woods, old fields, and along roadsides.

Suggested Uses

Grown in prairie and meadow plantings, native and wildlife gardens, and mixed borders for the airy purple seed heads and autumn colour. Used in restoration and as forage and cover on poor soils within its range.

How to Identify

Recognised as a tufted warm-season grass with narrow leaves and an open, widely branched flowering panicle held above the clump. In the purpletop the panicle turns purple to bronze and feels sticky or greasy to the touch. The greasy purple seed head and three-toothed flower scales separate Tridens spp. from other tall prairie grasses.

Appearance

Size & Dimensions

Height2' - 5'

Width/Spread1' - 2'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Summer Fall

The airy panicles open from mid to late summer and persist into autumn, turning purple and bronze. Flowers are wind-pollinated and inconspicuous in themselves. Seed ripens through autumn and the dry heads stand into winter.

Detailed Descriptions

Flower Description

purple to bronze

Foliage Description

green, bronze in autumn

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(Neutral)

357912

Soil Types

loam sand clay

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

These grasses grow in full sun to light shade in most well-drained soils across a pH of about 5.5 to 7.5, and tolerate poor, dry, and disturbed ground. Once established they need little water and stand up to heat and drought. The hardier species, including purpletop, are cold-tolerant to roughly zones 5 to 9. Increase is by seed sown in spring or by division of the clumps. The grasses can self-seed into bare ground, so seed heads are removed where spread is not wanted. Few pests trouble them, and they need no feeding on average soil.

Pruning

Clumps are cut back to a few inches in late winter before new growth begins. The dried panicles can be left over winter for structure and removed if self-seeding is a concern. Division every few years keeps the clumps vigorous.

✓ Toxicity

Non-toxic