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Aristida spp.

threeawns and wiregrasses

Poaceae

Warm regions worldwide; many species in the Americas, Africa, and Australia

Deer Resistant Drought Tolerant

Native to North America

SunFull Sun

WaterVery Low · drought-tolerant

HardinessZones 7–10

Overview

Aristida spp. is a genus of about 300 warm-season grasses in the family Poaceae, found in dry, open habitats across the warmer parts of every inhabited continent. Most species are tufted bunchgrasses 0.5-3 ft (15-90 cm) tall, forming narrow clumps of wiry, often inrolled leaf blades 2-12 inches (5-30 cm) long. The flowering panicles are narrow to open, 4-12 inches (10-30 cm) long, carrying slender spikelets whose defining feature is a lemma tipped with three awns 0.3-3 inches (0.8-8 cm) long. These three-pronged awns twist when wet, drilling the sharp-pointed seed into soil and into the coats and mouths of grazing animals, which limits the forage value of the genus. Plants grow actively in the warm season and cure to straw and pale gold as they dry. Members of Aristida spp. colonize sandy soils, eroded banks, overgrazed range, and roadsides, often increasing where heavier grazing has thinned more palatable grasses. Lifespan ranges from annual to long-lived perennial, and cold tolerance varies with origin.

Native Range

Distributed through the tropics, subtropics, and warm temperate zones worldwide, with many species native to the grasslands, deserts, and pinelands of the Americas, Africa, and Australia. Wiregrass (A. stricta and A. beyrichiana) is native to the longleaf pine savannas of the southeastern United States.

Suggested Uses

Used in habitat restoration, erosion control on sandy banks, and prairie and pineland plantings, with wiregrass being central to longleaf pine savanna restoration in the southeastern United States. The wiry clumps and airy seed heads suit naturalistic and dry-garden plantings. Most species carry low forage value and are managed on rangeland rather than sown for grazing.

How to Identify

Identified by narrow tufts of wiry leaves and by the seed, whose lemma carries three spreading or twisted awns, the feature that gives the threeawns their name. The slender spikelets each hold a single floret, unlike many co-occurring grasses with several florets per spikelet. The three-awned tip separates Aristida spp. from Stipa spp. and other needlegrasses, which bear a single awn.

Appearance

Size & Dimensions

Height6" - 3'

Width/Spread6" - 2'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks

Summer Fall

Most species flower from late summer into autumn (August-November), with some producing a second flush after warm-season rain. The narrow panicles emerge above the foliage and dry to pale straw as the awned seeds mature. Wind handles pollination, and the barbed seeds disperse on animal coats.

Detailed Descriptions

Flower Description

Green to straw

Foliage Description

Green to gray-green

Growing Conditions

Sun Requirements

SunFull Sun

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 Range5.0 - 7.5(Neutral)

357912

Soil Types

sand rocky

Drainagedry

Water & Climate

Water Needs

Very Low

Frost Tolerance

hardy

Time to Maturity

1-2 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grow in full sun on dry, infertile, sharply drained soils, especially sand and gravel where competition is low. Established plants are drought-tolerant and persist on ground too poor for most ornamental grasses, but they decline in rich, moist, or shaded soil. Perennial species are hardy in roughly USDA zones 7-10, with hardiness varying among the many species. Little watering or feeding is required once plants are established. On rangeland, threeawns increase under heavy grazing and signal declining pasture condition. The sharp awned seeds can injure livestock and work into clothing and animal coats.

Pruning

Old foliage on perennial species is cut or burned back in late winter before warm-season growth resumes, and fire-adapted wiregrasses respond to periodic burning with renewed growth and flowering. Annual species need no pruning and die after seed set. Removing seed heads before they ripen limits self-sowing and the spread of the barbed seed.