Side oats grama | The Morton Arboretum

Side oats grama was a common grass in both the tallgrass and shortgrass prairies, even though it is a shorter grass that grow to about 2 to 2 1/2 feet. It is most often found in drier areas away from the shade of the taller grasses. It is a warm season grass and considered a clumping grass, even though it sends out short rhizomes. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region, with updates made according to current research.

Family (English) Grass
Family (botanic) Poaceae
Tree or plant type Grass, Perennial
Native locale Chicago area, Illinois, North America
Size range Large plant (more than 24 inches)
Light exposure Full sun (6 hrs direct light daily)
Hardiness zones Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
Soil preference Dry soil, Moist, well-drained soil
Tolerances Alkaline soil, Dry sites, Occasional drought
Season of interest early winter, midwinter, midsummer, late summer, early fall, mid fall, late fall
Flower color and fragrance Purple
Shape or form Upright

Size and Form:

Side oats grama is an upright grass, growing 2 to 2 1/2 feet tall when in flower.

Native geographic location and habitat:

The species was commonly found in both the tallgrass and shortgrass prairies. It was common in drier areas of the prairie and away from the shade of the taller grasses. Native to the Chicago region. C-Value: 8.

Leaf description:

The leaves are up to 12 inches long, but very narrow at 1/8 inch. In summer, the leaves are gray-green. In autumn, the leaves take on purplish tones. During winter, the leaves are tan or straw-colored.

Flower description:

Flowering occurs in late summer (usually July to September). The tiny, purplish flowers are held on one side of an arching stalk. The flowers are wind pollinated.

Fruit description:

The small fruit (caryopsis or grains) form along the arched stalk that held the flowers. The fruits turn tan as they mature.

Plant care:

Side oats grama tolerates heat and drought well. While it is considered a clumping grass, it spreads very slowly by rhizomes. This is a warm season grass, so its most active growth occurs in summer. It will remain standing in winter and can act as winter interest. Since this grass remains attractive through winter, it should not be cut back until early spring, before new growth begins. At that time, it can be cut down to the ground.