Aristida purpurea
purple threeawn
Overview
Aristida purpurea is a warm-season perennial bunchgrass of dry plains, deserts, and disturbed rangeland across western and central North America. It forms dense, narrow-bladed tufts 1-3 feet (30-90 cm) tall and 8-18 inches (20-45 cm) wide, the green to blue-green leaves curling and fading to tan as they dry. From spring into fall, slender flowering stalks rise above the foliage carrying open, nodding seed heads that take on purple to reddish tints before aging to straw. Each floret bears three spreading awns 1-3 inches (2.5-8 cm) long, the trait behind the name threeawn. The sharp-pointed seeds twist into soil, fur, and clothing, and can lodge in the eyes, mouths, and hides of livestock, reducing the plant value as forage and contaminating wool. A deep, fibrous root system lets it hold dry, sandy, and rocky ground and recover quickly after grazing or fire, which is why it spreads readily on overgrazed and eroded land. It withstands heat, drought, and poor soil but adds little once the seed heads cure and drop. Plants are short-lived but reseed freely, so stands persist on bare, disturbed sites.
Native Range
Aristida purpurea is native to western and central North America, from the western United States and Great Plains south into Mexico. It grows on dry plains, mesas, desert grasslands, roadsides, and overgrazed rangeland, from low deserts to about 7,000 feet (2,100 m).Suggested Uses
Used in dryland and native restoration seedings, erosion control on sandy slopes, and low-water ornamental plantings for its purple summer seed heads. Grazed lightly by livestock before the awns harden. The sharp awned seeds leave it unsuited to pastures relied on for forage or to plantings near paths and animals.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread8" - 1'6"
Colors
Bloom Information
Flowering stalks appear from spring through fall, with the heaviest set after spring or summer rains. The seed heads flush purple to red before drying to tan. Awned seeds shed through summer and fall and twist into the soil surface as they wet and dry.
Detailed Descriptions
Flower Description
purple to reddish, aging tanFoliage Description
green to blue-green, curling and tan when dryGrowing Conditions
Sun Requirements
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