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Grasses of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

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Common Name
Prairie Dropseed

 

Scientific Name
Sporobolus heterolepis (A. Gray) A. Gray

 

Plant Family
Grasses (Poaceae)

Garden Location
Not in the Garden

 

Prime Season
Late Summer flowering

 

Grass structure and definitions - PDF from Oregon State University

Ligule Types, Shapes & Margins (pdf)

 

Prairie Dropseed is a warm season perennial grass, growing 2 to 4 feet high, which forms large clumps or tufts. It is a plant typical of tall grass prairies. It can be used for ornamental purposes as the clumps have a fine round shape, the leaves form a drooping cascade beneath the fine flowering stems. It is particularly attractive in a massed grouping

The leaves (blades) are about 3 mm wide, up to 12 inches long, flat to slightly rolled (at least rolled at emergence from the sheath), distinctly veined to a pointed tip. The upper surface is smooth but the margins are rough. Leaves are held ascending initially but are drooping in a cascade at flowering time.

The leaf sheath is flattened, split, and distinctly veined like the leaf. The margins are somewhat translucent, the base may be whitish or purplish and with or without some fine hair.

The collar is yellowish-green and finely hairy on the margins. There are no auricles.

The flowering heads are terminal on the stems and held erect well above the leaf blades. The head is an open panicle, pyramidal in shape, up to 9 inches high and half as wide as the height. The primary branches of the panicle are upright to spreading (as much as 70 degrees from the central rachis).

Spikelets appear loosely arranged on the upper 2/3rds of the branches of the panicle. Where the small branches attach to the main stem, the stem is slightly swollen, and in the lower 1/3 of the branches of the panicle there is an elongated gland which produces an aromatic scent - one of the few grasses to have a scent during flowering. The spikelets themselves are elongated, 3 to 6 mm long, slightly reddish to straw-colored, with one floret per spikelet that usually has 3 anthers that are yellowish to purplish. The glumes covering the forming seed are lanceolate in shape and unequal in size, the lower 1.8 to 4.5 mm long, the upper 2.4 to 6 mm long. Lemmas are pointed and without hair and slightly shorter than the paleas.

Mature fruit is a round to pear-shaped hard, smooth and shiny seed, light brown to gold in color. One of few native grasses to produce such a seed. Seeds weigh about 16,000 to the ounce. They disarticulate above the glumes. Seeds can germinate without prolonged cold or warm stratification, but if stored, should be stored in cold dry storage.

 

Habitat: Being a plant of the tall grass prairie, Prairie Dropseed grows best in sandy to loamy soils, with dry to moderate moisture conditions and full sun. Less that full sun will cause lodging of the flowering heads. The root system is fibrous, not rhizomatous.

Names: The genus name, Sporobolus, is taken from two Greek words - sporo meaning 'seed' and ballein, meaning 'to throw' or 'to cast forth' which together refer to the tendency of the seeds to be energetically released when they are dry. The species, heterolepis, is again, taken from two Greek words - heteros, meaning 'different' or 'varied' and lepis, meaning 'scale', together referring to the unequal size of the glumes of the spikelet. The doubled name of the author of the plant classification -  ‘A.Gray’ refers to Asa Gray (1810-1888), American botanist, Professor of Natural History at Harvard and instrumental in unifying plant knowledge of North America and author of Gray’s Manual - Manual of the Botany of the Northern United States, from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive. His name is repeated as he later published an amended description of his earlier work.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Plant Seed

Above: The two characterists of the plant are shown above - the graceful arching thin leaves forming a cascade and the pear-shaped shiny fruits.

Below: The seed panicle as it develops is open with wide spreading branches. Drawing courtesy of University of Wisconsin, Drawing by Agnes Chase from Norman C. Fassett's Grasses of Wisconsin.

seed  panicle drawing

Below: 1st photo - A typicle seed panicle with the spikelets on the upper 2/3rds of the side branches. 2nd photo - a spikelet at flowering time with anthers and stigma visible. 3rd photo - the split leaf sheath and collar area that may have or not have hair.

seed head flower ligule

Below: The leaf blade surface is fairyly smooth but the margins are rough to the touch.

leaf blade

Below: When Prairie Dropseed is mature, the flowering seed panicles can provide a dense mass of fine texture above the cascading leaves, especially in a mass grouping as seen here.

plant group

Below: Prairie Dropseed is a tuft forming grass. This clump is 4 years old.

tuft

Notes:

Prairie Dropseed is native to Minnesota, being found in most counties west and south of a diagonal line drawn from Chisago northwestward to Roseau. This area excludes basically the NE quadrant of the state but would include the metro area but the grass is absent in the south metro counties of Carver, Scott and Dakota. In North America it is present from the Rocky Mountains eastward except for the southern tier of states, New England, and the Canadian Maritime Provinces. It is considered endangered or threatened in at least several eastern states.

There are numerous species of the genus Sporobolus. Within Minnesota five are recognized: S. compositus, Composite Dropseed; S. cryptandrus, Sand Dropseed; S. heterolepis, Prairie Dropseed; S. neglectus, Puffsheath or small Dropseed; and S. vaginiflorus, Poverty Dropseed. Most are widely found.

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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