Aristida

( ar - RISS - ti - duh )

At-A-Glance Information

Commonly called Three-Awn, Wiregrass, Speargrass, or Needlegrass, this genus of perennial grasses includes species which need full sun and little to no water to perform well. Species are found worldwide. They add airy, silvery-purple texture and movement in landscapes. These grasses are used in mixed beds, borders, and water-wise and native gardens are great for a flowering accent among boulders or cacti. Take care when planting these grasses in the landscape, as they produce sharp awns that can injure grazing animals. These grasses have also been identified as highly flammable, and should not be planted close to structures or in wildfire-prone areas.

Aristida species and Varietals

The genus Aristida is a member of the plant family Poaceae and includes around 300 species. This grass grows well in Sunset zones 3b-24 or USDA zones 5-12, though this varies somewhat depending on the species grown. For more information, see the species descriptions below. To find your zone, click here: Zone Map.

Aristida basiramea (Forked Three-Awn, Forktip Three-Awn, Base-Branched Three-Awn)
These annual grasses freely branch out from their base, and reach up to between 8 and 24 inches tall when mature. Leaves are narrow. Flowers are present between the months of August and October, adding an airy feel to landscapes. These grasses grow well in USDA hardiness zones 2-11.

Aristida californica (California Threeawn, Mojave Threeawn)
These grasses are clump-forming and hairy, and reach about 16 inches tall when mature. They typically grow in sandy areas, and are native to the Mojave and Sonoran Deserts of northern Mexico, California, and Arizona. The key for the survival of these grasses are a desert climate and sandy soil.

Aristida calycina (Dark Wire Grass, Branched Wiregrass)
These grasses are native to Australia, and have a loosely tufted habit. Individual plants reach between a foot and six feet seven inches tall when mature and in bloom. They grow well in sandy and poor soils within their native range, and produce purplish spikelets in spring and summertime.

Aristida contorta (Bunched Kerosene Grass, Kerosene Grass, Bunched Windgrass, Silvergrass, Mulga Grass, Sand Speargrass)
These grassland plants, native to Australia, are short-lived perennials with a tufted habit. They typically grow to reach between 5 inches and 1.5 feet tall when mature. Flowers bloom between February and June, and are brown. They grow well in USDA hardiness zones 8a-11b.

Aristida dichotoma (Churchmouse Threeawn, Fork-Tip Three-Awn, Pigbutt Three-Awn, Poverty Grass, Beard Grass, Branching Aristida)
This species of grasses is native to an area that spans from the eastern and midwestern United States through Ontario, Canada. It is considered an introduced species in California, but is not labeled as invasive. These plants grow well in USDA hardiness zones 4-9.

Aristida purpurascens (Arrowfeather Threeawn, Purple Threeawn)
Native to eastern North America down through Honduras, these grasses lack rhizomes and can grow in moderate shade. Individual plants typically reach between 1 and 2 feet tall when mature and up to 3 feet when in flower. Grows well in disturbed soils. Best in USDA hardiness zones 7-11.

Aristida purpurea (Purple Three-Awn, Purple Threeawn Grass)
This species is native to North America, and has a widespread distribution across the western 2/3rds of the United States, southern Canada, and northern Mexico. They grow well in plains landscapes. These perennial bunchgrasses reach up to 3 feet tall when mature and in bloom, and flowers are light brown to purple in color. Hardy to -20 degrees Fahrenheit. Best in USDA hardiness zones 5-10.

Aristida stricta (Chaetaria stricta) (Wiregrass, Pineland Three-Awn Grass)
These plants are common understory plants on sandhills and flatwoods coastal plains ecosystems in the Carolinas. The plant actually gave the region one of its nicknames (The Wiregrass Region). This is a vigorous, fast-growing species that can regenerate quickly after fires, and actually needs regular summer burning to stimulate flowers and set seed. Best in USDA hardiness zones 7a-9b.

Aristida tuberculosa (Seaside Threeawn, Seabeach Needlegrass, Beach Three-Awned Grass, Beach Needlegrass)
This annual species is native to the United States, and is considered endangered in Connecticut, New Hampshire, Indiana, Massachusetts, and Michigan. Individual plants reach up to between 10 and 12 inches tall when mature and in bloom. It has an overall coppery hue from afar, and grows well in sandy soils.

Caring for Aristida

Take care when planting these grasses in the landscape, as they produce sharp awns that can injure grazing animals. These grasses have also been identified as highly flammable, and should not be planted close to structures or in wildfire-prone areas. These warm-season ornamental grasses are typically considered weedy, though some species, particularly Aristida purpurea (Purple Three-Awn) is a popular ornamental plant. Install grasses 2-3 feet apart for best coverage and airflow. Plant in full sun; ideally, they like to receive between 6 and 8 hours of direct sun each day for best growth rate and color. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.5 and 7.5 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these grasses are considered drought-tolerant, and can get by on little water.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. These plants will re-seed freely in the garden; to discourage this, make sure to remove flower spikes before they set and release seed. Volunteer seedlings are easily pulled from areas where they are unwanted, and can be transplanted elsewhere or composted.

Propagation

Aristida, or Three-Awn, is best propagated by seed. Plants will re-seed freely in the garden, and these volunteer seedlings can be dug up and transplanted elsewhere. To propagate your Three-Awn grass, follow the instructions below:

Propagating Aristida by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag and a pot or tray filled with well-draining compost or other organic material. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Cut them off of the plant, placing them in a paper bag. Harvest as many as possible. Once harvesting is complete, bring the seed heads inside. Separate each seed from its attachment to the stem.
Get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 1-3 weeks from sowing.
Keep the seedling's potting medium moist, but not wet. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist until the next spring (after the danger of frost has passed), when you can transplant the grass to its new home out in the landscape.

Three-Awn grasses produce spiky-looking seed heads.

Seeds are long and thin with feathery attachments.

Problems and Pests

Aristida grass species are typically considered resilient in landscapes, though they can be susceptible to developing problems with the following pests and diseases from time to time: