Arrhenatherum

( ah - ren - AH - ther - um )

At-A-Glance Information

Commonly called Bulbous Oat Grass, Tuber Oat Grass or Button-Grass, this perennial grass has narrow leaves that are boldly edged and striped with white. These grasses require full sun to partial shade and regular waterings to perform well in the landscape. Button Grass is a great candidate for perennial borders or large rock gardens, and can brighten up dark areas under trees and shrubs. Plants typically form a 1-foot high clump and produce flowering stems up to 2 feet tall in summertime. The genus Arrhenatherum is in the plant family Poaceae and includes 7 species, only one of which (Arrhenatherum elatius) is commonly grown as a garden ornamental. This grass grows best in USDA hardiness zones 4-9 or Sunset growing zones 1-7, 15-17, 23 and 24. To find your zone, click here: Zone Map. Take care when planting these grasses in the landscape, as they are considered invasive in many areas of North America.

Caring for Arrhenatherum

This cool-season grass prefers areas with cool nights and dry summers, and is best in low-heat areas. They tend to go dormant with increased temperatures, but will regrow from the base in fall. Use these grasses as accents in mixed beds or borders, as a small-space groundcover, or in containers. Space these grasses between 1 and 2 feet apart for best coverage and airflow. Plant Button Grass in an area that receives full sun to partial shade. Ideally, they should be getting around 6 hours of sun each day, but appreciate 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 8.0 (acidic to 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 are considered drought-resistant, able to get by for most of the year on rainwater alone, with supplemental 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. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season. Heat can cause these grasses to become floppy and limp; if this happens, simply shear them to encourage fresh growth in fall. If your plant is spreading too much or in an unwanted direction, simply curtail growth by dividing clumps and replanting them elsewhere or composting them. Arrhenatherum grasses are considered long-lived perennials in the landscape, regrowing from an underground root system each growing season.

Propagation

Arrhenatherum grasses are best propagated by division; for instructions on how to propagate Bulbous Oat Grass, see below:

Propagating Arrhenatherum 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 (after the plant has entered dormancy, but before it has begun its new spring growth), 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 root(s). Once you have worked it up out of the ground, lay it out.
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.

Problems and Pests

Take care when planting these grasses in the landscape, as they are considered to be invasive in North America. Check with local authorities before planting. Arrhenatherum, or Tuber Oat Grass, is susceptible to developing issues with the following: