Broad-leaf wood-oats (Chasmanthium latifolium) is a very unique plant that goes by many names:
- Spangle grass.
- Indian wood-oats.
- Wild oats.
- River oats.
- Northern sea oats.
- Inland sea oats.
The spikelets are the most distinctive feature, being flat, broadly oblong, and about 1/2 inch to 1-1/2 inch long and 1/2 inch to 3/4 inch wide. These spikelets have no awns. They are green when young and fade to a pale, tawny color when mature. They grow on long, threadlike stalks, creating an inflorescence that is drooping overall.
But do not fail to note the other interesting features of broad-leaf wood-oats. This plant is two to four feet high and grows upright, perhaps with a few branches. Its stem is hollow and ribbed.
The leaf blades are flat with conspicuous midribs and rough margins. They vary considerably in length, measuring anywhere from 2 to 8-1/2 inches. They are 1/4 inch to 1 inch wide. The leaves are bright green most of the year, but they become copper-colored after the first frost.
This grass spreads by means of short, thick rhizomes. It grows in clumps that can be more than 2 feet across. Broad-leaf wood-oats has a fibrous root system.
Broad-leaf wood-oats is native to the southeastern United States, putting Kansas on the western edge of its range. It occurs only in the eastern half of Kansas, usually in wooded areas and floodplains.
This plant is very tolerant. While it prefers moist soils, it can grow in drier soils provided they are shaded, as it is drought-resistant once established. However, it is not likely grow from seed in such areas. Where soils are moist, it can adapt to full sun but will grow shorter. Broad-leaf wood-oats likes fertile soils, but can persist in sandy soils low in nutrients, as well. It prefers a soil pH that is neutral to slightly acidic. It can survive black walnut but not salt.
Broad-leaf wood-oats is considered a short-lived perennial. It flowers from July through September in Kansas. The seed heads remain on the plant through the winter.
This native plant provides seeds as food for birds and other wildlife. It is also a host plant for several species of skipper butterflies.
Although broad-leaf wood-oats is acceptable as a forage plant for cattle, it is not prevalent enough throughout Kansas to be of particular interest.
Where broad-leaf wood-oats can really shine is as a low-maintenance ornamental in shady areas and around water gardens. Its seed heads will remain standing throughout the winter, giving you something to look at in bleak weather. Broad-leaf wood-oats can also be an attractive touch to dried floral arrangements. You can plant the seeds year-round, but for best results plant them in early spring, just barely covered with soil and about one to two feet apart. This spacing may seem a little wide at first, but the clumps will slowly spread. Once the clumps are established, divide them in the spring whenever they seem to have lost their vigor. Leave the foliage standing over the winter to protect the crowns.
Native Americans sometimes ground the seeds of this plant to make flour.
In nature, broad-leaf wood-oats presents no hazards.
As a garden plant, this species may become mildly invasive in moist areas.
Broad-leaf wood-oats is very distinct in appearance, even when it is not flowering (note the unusually broad leaves). It should present few identification challenges.
Parts of a Grass Plant: A Glossary
Definitions for technical terms used in this post.