Chasmanthium

( kaz - MAN - thi - um )

At-A-Glance Information

This genus of perennial grass (commonly called Sea Oats or Bamboo Grass) includes species which form clumps of broad, bamboo-like stems that support flowers in summertime. Spikelets resemble flat oats and turn copper in fall and dry to a green color; they are beautiful in dried arrangements. The genus Chasmanthium includes 5 species (only one of which is commonly grown as a garden ornamental) and is a member of the plant family Poaceae. Bamboo Grass grows well in USDA hardiness zones 3-9 or Sunset growing zones 2-10 and 14-24. To find your zone, click here: Zone Map. Use these grasses to add texture and movement to prairie, native, or informal meadow landscapes or simply grow them as members of cut flower gardens.

Caring for chasmanthium

Plant Chasmanthium, or Bamboo Grass, in a space in the landscape that receives full sun to partial shade. In warmer climates, make sure they are getting some late afternoon shade when temperatures are at their peak. They prefer soil to be well-draining, moderately fertile, and to have a pH of between 4.5 and 7.0 (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 to be relatively drought-tolerant, able to get by on rainwater for much of the year with supplemental waterings during extended periods of drought. Regular waterings, however, will ensure that these grasses will maintain peak health. Water deeply once a week during the active growing season, and withhold water in wintertime. Make sure to avoid overwatering or planting these grasses in a depressed area of the landscape where water accumulates. They do not like having standing water around their root systems, which can quickly lead to root rot.

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. The appearance of this grass can be improved by removing any dead growth in early spring. Needs to be cut back to between 6 and 10 inches tall in late winter every couple of years to encourage new foliage to grow and to keep plants growing vigorously. Every few years, especially if these grasses are grown in a cramped border or container, they will need to be divided to ensure ongoing health. For instructions on how to successfully divide Anemanthele plants, see the Propagation section below. Chasmanthium is a perennial grass that will persist in the landscape for many years before needing to be replaced. These grasses will freely re-seed, as well, providing plants in the landscape (as well as neighboring ones) indefinitely.

Harvesting Chasmanthium
In addition to being wispy additions to landscapes, these grasses are also cultivated for their cut flowers, which are used in both fresh and dried arrangements. They add airy texture and height, and are typically harvested in mid summer to early fall. Foliage color becomes most vibrant at this time of the year. Use a sharp, clean pair of pruning shears or snips to avoid damaging stems and prevent the spread of disease. Cut at the base of stems, and immediately drop them into a bucket of cool water. Fresh stems have a vase life of about two weeks. To dry stems, bunch them and hang them upside down in a cool, dark, dry area after harvesting. Once completely dried, handle with care to avoid breaking the brittle stems. They can be added to long-lasting dry bouquets, wreaths, or used in other floral crafts.

Propagation

Chasmanthium, or Bamboo Grass, is propagated through volunteer, division or seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant, especially if you are propagating a hybrid cultivar. To propagate your Bamboo Grass, follow the instructions below:

Propagating Chasmanthium 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, a pot or tray filled with well-draining compost or other organic material, and a spray bottle. 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 your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded, and are typically held above the foliage on thin stems. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Chasmanthium seeds will need a period of cold-stratification in order to germinate. To complete this process, first place seeds in a bag or other sealable container filled with moistened sand or peat moss. Then, place the container in the refrigerator (or similarly cool, dark space) for 2-3 months. The ideal temperature for cold-stratification is around 40 degrees Fahrenheit. After this period has passed, remove seeds from the container.
Get a sowing container prepared. Water the prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place the seeds about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. 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 7-14 days from sowing.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. 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, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Chasmanthium 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 early spring or fall. 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.
Separate the removed patch of grass into sections using a sharp, clean knife or trowel. Ensure that each division has a healthy root system and a few shoots. Any dried out areas with dead roots can be tossed in the compost.
Prepare your pot(s) or new planting site(s) with well-draining soil and compost and work it in. Water thoroughly, and then plant divisions.
Keep soil consistently moist as the newly-planted divisions establish strong root systems in their new home. Provide regular waterings, especially during dry spells.

Propagating Chasmanthium by Volunteer

Volunteer seedlings are likely to pop up for miles around these grasses, as they have a tendency to re-seed prolifically. When they appear, they can be dug up and replanted elsewhere. To propagate your plant via volunteer seedlings, you'll need a garden shovel, potting soil, and a pot (if you won't be replanting it immediately in your garden).
Dig up your volunteer shrub using your garden shovel, being careful to not damage the roots. Then, either in a pot or a prepared spot in the garden, replant it. Water it in, and continue providing regular waterings until the shrub has established itself in its new home. Then, resume regular care instructions.

Problems and Pests

These grasses, while not officially listed as invasive, will re-seed and spread aggressively in sunny, moist areas, and therefore can themselves be considered pests in the landscape. Chasmanthium, or Sea Oats, is generally resistant to pests and diseases, though it can develop problems with the following from time to time: