Sorghastrum

( sor - GAS - trum )

At-A-Glance Information

Indian Grass is a genus of ornamental grass species that need full sun to perform well in the landscape. Species are native to the Americas and Africa and have varying water needs. They form loose, upright clumps of foliage that can be green, blue-green or greyish, turning orange, purple or yellow in fall. They typically reach between 3 and 8 feet tall, and feature vertical flowering stems topped with feathery panicles. These grasses will attract birds and butterflies to the garden. The foliage is used in fresh or dried arrangements. Use Sorghastrum grasses to add vertical interest to mixed beds and borders, as erosion control on slopes, mass plantings in meadow or prairie landscapes, or in rain gardens or bioswales.

Sorghastrum Species and Varietals

The genus Sorghastrum is a member of the plant family Poaceae and includes 22 distinct species. The grasses in this genus are related to those in Zea (Corn), Imperata (Satintails), Miscanthus (Silvergrass), Andropogon (Bluestem) and Schizachyrium (Bluestem). Sorghastrum grasses grow well in USDA hardiness zones 2-9, though this varies somewhat depending on the species cultivated. For more information, see the species descriptions below:

Sorghastrum nutans (Indiangrass, Indian Grass, Yellow Indian-Grass, Wood Grass)
This species is native to the United States and Canada, and reaches up to between 3 and 7 feet tall at maturity. Panicles of branched clusters of golden-brown flowers are present in late summer followed by seed heads in fall. Cultivars of this ornamental species include 'Golden Sunset' (to 5-6 feet with long, golden-yellow seed heads in summer), 'Cheyenne' (with great drought tolerance), 'Indian Steel' (with steel blue foliage and tan flower spikes, gold fall color), 'Slim Pickens' (to 30 in. tall), 'Llano' (xeric variety with blue foliage), and 'Sioux Blue' (with blue foliage).

Caring for Sorghastrum

Space these grasses between 18 and 36 inches apart for best coverage and airflow as a dense groundcover or screening plant. In general mixed borders, the can be spaced about 2 to 3 feet away from other plants, and as specimens they should be given 3 to 6 feet of space. Plant in an area that receives full sun; ideally, they should be getting between 6 and 8 hours of sun each day, but do appreciate some late afternoon shade when temperatures are at their peak. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.5 to 8.0 (acidic to slightly alkaline). 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 plants have low to moderate water needs depending on the species grown. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch, and provide deep waterings during extended periods of dry weather.

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. Prune in late winter or early springtime just before new growth begins to emerge, and then cut all foliage down to between 1 and 2 inches from the soil surface. Sorghastrum are long-lived perennials, and can survive in the landscape for between 15 to 20 years or more before needing to be replaced. They will spread efficiently in the landscape to form cohesive colonies, providing new plants for the garden indefinitely.

Caring for Sorghastrum in Containers
Sorghastrum can be used as a 'thriller' plant in container arrangements or stand alone as an architectural statement. Cultivars ideal for container cultivation include 'Slim Pickens', 'Indian Steel', and 'Thin Man'. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away from the root zone. Fill with a well-draining potting mix amended with organic material, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and increase soil moisture retention. These grasses require consistently moist soil to thrive; as a general rule of thumb, water every day in the summer. During the rest of the year, water whenever the top inch of soil feels dry to the touch. Sorghastrum grown in containers will need more frequent irrigation than those grown in the ground. Prune in late winter or early springtime just before new growth begins to emerge, and then cut all foliage down to between 1 and 2 inches from the soil surface. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that the plant needs to be potted up; choose a slightly larger container and repot. These plants will need to be divided every once in a while to maintain their health (and the health of plants around them). For instructions on how to divide Sorghastrum grasses successfully, see the Propagation section below.

Harvesting Sorghastrum
Sorghastrum grasses are grown for their upright spikes of flowers and subsequent seeds, which can be used in fresh and dried floral arrangements. They are typically available at the end of summer through fall. The best time of day to harvest cut flowers is in the morning, after dew has dried but before the heat of the day sets in. Harvest when plumes are fully colored but still tight. Using sharp, clean snips or shears, sever the stem from the plant and drop it into a bucket of cool water. They will last for between 7 and 10 days in a vase. To harvest seed heads for dried flower arrangements, wait until the flower heads have opened up and developed seeds. They should be harvested after the seeds are fully formed but before they become brittle and shatter or begin shedding. Harvest the stems using sharp, clean shears or snips and carefully bundle them together. Too much shaking or jostling can dislodge the seeds. Bundle a few stems together loosely with a rubber band or twine. Hang the bunches upside-down in a dark, warm, dry room with good airflow. They should be completely dried in about 2 weeks. Stems should snap easily when bent. Treating them with floral sealer spray after drying can ensure that seeds remain in place for a longer amount of time. Dried Sorghastrum seed heads can last for between 1 and 3 years time if kept out of direct sunlight and humid conditions.

Propagation

Sorghastrum, or Indian Grass, is best propagated through division of existing plants; for instructions on how to propagate Sorghastrum plants, see the instructions below:

Propagating Sorghastrum by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring, and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate Sorghastrum by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the roots. Once it is worked up out of the ground, lay it out. Remove any dirt or debris from the roots.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home.