Imperata

( im - puh - RAH - tuh )

At-A-Glance Information

Commonly called Cogongrass, this genus is filled with perennial grass species which grows from rhizomes and forms clumps of blades. Species have moderate to high water needs, and prefer to be situated in full sun. The most popular ornamental species in the genus is Imperata cylindrica, which includes the cultivar 'Red Baron', and is commonly called Japanese Blood Grass. Use these grasses to naturalize in informal, meadow, or prairie landscapes, or simply as an ornamental grass in mixed beds, borders, or containers. Take care when planting these ornamental grasses in the landscape, as leaf margins are finely toothed and can cause skin irritation when handled.

Imperata Species and Varietals

The genus Imperata is a member of the plant family Poaceae and includes 11 species. Plants in the genus are closely related to those in Miscanthus. Imperata plants grow well in USDA hardiness zones 5a-9b or Sunset growing zones 4-24, though this varies somewhat depending on the species grown. To find your zone, click here: Zone Map.

Imperata brevifolia (Mexican Satintail, California Satintail)
This rare species is native to the southwestern United States (from California through Texas) and northern Mexico. It produces a perennial clumping grass to 3-4 feet tall. Flowers form on cylindrical bright white 5-foot tall plumes from late summer through fall. This species grows well in USDA hardiness zones 8-11 and is an aggressive spreader, but is not considered invasive.

Imperata cylindrica (Cogongrass, Kunai Grass, Cogon Grass, Blady Grass, Satintail, Spear Grass, Sword Grass, Thatch Grass, Alang-Alang, Lalang Grass, Cotton Wool Grass, Kura-Kura, Keri)
Native to Asia, Micronesia, Melanesia, Australia, Africa, and Southern Europe, this species forms a clumping grass to 10 feet tall. Foliage is green and fades to copper. Leaf margins are finely toothed. Flowers are small, and held on feathery stalks that are held slightly above foliage. This species is considered invasive across the southeastern United States, Africa, and Central America. Colorful-foliaged cultivars have been bred from the straight species, including:

'Red Baron'
To 1-2 feet tall with striking cranberry-red tipped foliage.

'Rubra'
With deep, burgundy-red tipped foliage. Cold tolerant.

Caring for imperata

Take care when planting these ornamental grasses in the landscape, as leaf margins are finely toothed and can cause skin irritation when handled. Space these grasses between 12 and 18 inches apart for best coverage and airflow as a dense groundcover. They can be spaced 3 feet apart from each other and other plants if being used as an accent feature. These grasses will spread aggressively through the landscape via hard underground rhizome roots if not contained; root barriers are strongly recommended for control. 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 4.5 to 6.0 (acidic to slightly acidic). 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 appreciate consistently moist soils, and can be grown along pond edges or in riparian areas. Reduce waterings during wintertime when grasses are dormant.

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. Cogon Grasses are long-lived perennials, and can survive in the landscape for between 7 and 10 years. They will form colonies via underground rhizomes which can be dug up and divided, providing plants for the landscape indefinitely.

Caring for Imperata in Containers
Imperata, most commonly Japanese Blood Grass, is used as a 'thriller' plant in container arrangements. Choose a container that is at least 1 to 5 gallons and between 18 and 24 inches wide. 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. Imperata plants 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 successfully divide Imperata plants, see the Propagation section below.

Propagation

Imperata, or Blood Grass, is best propagated through division of existing plants; for instructions on how to propagate Cogon Grasses, see the instructions below:

Propagating Imperata 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 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 rhizome 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.

Problems and Pests

Certain species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Imperata, or Cogon Grass, is an amazingly resilient plant that does not have any major pest or disease issues in the garden. For information on commonly encountered pests and diseases in the landscape, consult the following pages:

Pests & Pest Management

Plant Issues