Hesperostipa comata (Needle-and-thread Grass)

Plant Info
Also known as:
Genus:Hesperostipa
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:sun; dry sandy soil; prairies, grasslands, open woods
Fruiting season:July - August
Plant height:12 to 40 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: panicle Cluster type: raceme

[scan of panicle] Branching cluster (panicle) 4 to 8+ inches long at the top of the stem, sometimes erect but typically nodding, the main branches ascending to arching, with 1 or 2 spikelets (flower clusters) per branch. The base of the panicle is often partially hidden in the uppermost sheath. Spikelets are short to long-stalked, single-flowered, 15 to 35 mm (~½ to 1 1/3 inch) long, narrowly lance-elliptic in outline.

[close-up of branches] At the base of a spikelet is a pair of bracts (glumes), both similar, thin, hairless, 5-veined, 15 to 35 mm long, the lower glume slightly longer than the upper glume but both longer than the floret, narrowly lance-shaped with a long taper to a pointed tip that may extend to an awn up to 7 mm long. Florets are surrounded by a pair of bracts (lemma and palea), the lemma thicker than the glumes, 5-veined, 7 to 13 mm long, evenly covered in short white hairs, narrowly lance-linear with a stiff awn 4 to 8 inches long; the palea is about as long as the lemma and mostly hidden by it. The thickened base of the floret (callus) is 2 to 4 mm long and covered in straight, light brown hairs.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath, ligule and stem] Leaves are basal and alternate on the lower stem, .5 to 4 mm (to 1/6 inch) wide, basal leaves up to 16 inches long, stem leaves to 12 inches long, hairless on the lower surface, usually rough and minutely hairy on the upper surface, the edges often rolled in (involute). Sheaths on lower stem leaves may be minutely hairy on the surface. The ligule (membrane where the leaf joins the sheath) is up to 7 mm (~¼ inch) long and usually jagged across the top edge. Nodes are mostly smooth, or the lower nodes with a few hairs; lower nodes are usually hidden by the sheaths. Stems are mostly smooth except at the nodes.

Fruit: Fruit type: seed without plume

[photo of mature spikelet] At maturity, glumes turn pale and florets straw-colored to light brown, the florets shedding individually leaving the glumes behind on the stalk. The floret base has a needle-like point and the stiff hairs on the surface cause it to attach to anything unlucky enough to pass by. The long awn twists in response to changes in moisture, coiling and uncoiling as it dries, usually loosely curled above the spirally twisted base, and eventually drills into the ground. Grains (seeds) are light brown, linear, 2 to 4 mm long.

Notes:

Needle-and-thread Grass is a common grass of the Great Plains and reaches the eastern edge of its native range in Minnesota; it's considered introduced farther east. There are 3 Hesperostipa (formerly Stipa) species currently known to be in Minnesota; of these, only H. comata has curling awns, lemmas evenly covered in white hairs all across the surface, and may have short awns on glumes. The other two have lemmas with bent and twisted awns, the surface unevenly covered in brown hairs and usually hairless on the tip half except on the veins, and glumes taper to a slender, pointed tip but are not awned. Hesperostipa spartea (Porcupine Grass) is generally a larger, more robust plant, with lemmas up to twice as long as H. comata, lower nodes usually have lines of fine hairs and lower sheaths are usually fringed along the edges; H. curtiseta (Western Porcupine Grass) has florets like H. spartea but smaller, and its lower ligules are often higher on the sides with a minute fringe of hairs across the top. Later in the season after florets drop off the length of persistent glumes combined with ligules, nodes and sheaths may help distinguish these three.

There are 2 recognized subspecies of H. comata: subsp. comata, the more common of the two and found in Minnesota, has curling awns 3 to 8+ inches long, the lower stem nodes are usually hidden by the sheaths, the panicle is often partially enclosed by the upper sheath, and prefers open grasslands; subsp. intermedia, found in the western third of North America, has generally straight awns 2½ to 5 inches long, the lower nodes are all exposed, the panicle is fully extended out of the upper sheath, and prefers open pine woods;

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More photos

Photos by K. Chayka taken in Lac Qui Parle and Polk counties. Photos by Peter M. Dziuk taken in Lac Qui Parle, Ottertail and Polk counties.

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