Hesperostipa spartea (Porcupine grass)
|Also known as:||Needlegrass|
|Habitat:||sun; dry sandy or gravelly soil; open prairie|
|Plant height:||2 to 4 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Branching cluster 4 to 10 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. Spikelets are short to long-stalked, single-flowered, 30 to 40 mm (1 to 1½ inches) long, narrowly lance-elliptic in outline.
At the base of a spikelet is a pair of bracts (glumes), both similar, thin, hairless, 5 to 7-veined, 30 to 40 mm long, longer than the floret, narrowly lance-shaped with a long taper to a pointed tip. Florets are surrounded by a pair of bracts (lemma and palea), the lemma thicker than the glumes, 5-veined, 13 to 25 mm long, hairy, narrowly lance-linear with a stiff awn 4 to 8 inches long covered in short, stiff hairs; the palea is about as long as the lemma and similarly hairy. The thickened base of the floret (callus) is covered in straight, brown hairs.
Leaves and stems:
Leaves are basal and alternate on the lower stem, 1.5 to 4.5 mm (to 1/6 inch) wide, basal leaves up to 2 feet 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 hairy along the edges but most are smooth. The ligule (membrane where the leaf joins the sheath) on lower leaves is up to 3 mm long, usually rounded or straight across; upper leaf ligules are up to 7.5 mm (~1/3 inch) long and more ragged across the top edge. Nodes are mostly smooth, or the lower nodes with a few hairs. Stems are smooth in the lower plant, becoming rough and somewhat hairy in the upper.
At maturity, glumes turn pale and florets medium to dark 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 bent once or twice above the spirally twisted base, and eventually drills it into the ground. Grains (seeds) are light brown, linear, 3.5 to 6 mm long.
It can genuinely be a miserable experience to hike through a prairie full of Porcupine Grass when it is shedding its seed. Poke, poke, poke! There are 2 Hesperostipa (formerly Stipa) species in Minnesota; Hesperostipa comata (Needle-and-thread grass) is generally a smaller plant, with spikelets essentially ½ to 2/3 the size of H. spartea and its awn more slender and more curling.
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- comparison of mature Hesperostipa spartea and H. comata florets
- Porcupine grass plants
- early season plants
- later season leaf clump
- sticks to everything
- Porcupine grass habitat
- close up of lemma and callus hairs
- close up of twisted awn
Photos by K. Chayka taken at Long Lake Regional Park, Ramsey County. Photos by Peter M. Dziuk taken in Anoka and Pope counties.
Have you seen this plant in Minnesota, or have any other comments about it?