Hesperostipa spartea (Porcupine grass)

Plant Info
Also known as: Needlegrass
Genus:Hesperostipa
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:sun; dry sandy or gravelly soil; open prairie
Fruiting season:spring
Plant height:2 to 4 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: indistinct Cluster type: panicle

[close-up of flowering panicle branches] 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.

[photo of spikelet] 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: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath, ligule and leaf] 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.

Fruit: Fruit type: seed without plume

[photo of mature florets dropping off] 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.

Notes:

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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More photos

Photos by K. Chayka taken at Long Lake Regional Park, Ramsey County. Photos by Peter M. Dziuk taken in Anoka and Pope counties.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Jason - Arlington
on: 2013-07-07 20:09:13

Porcupine grass is giving up it's seeds right now in my area. It is most certainly true how the awns twist in response to moisture differences. Bringing a bag of seeds from the humid outdoors into an air conditioned car is interesting to say the least!

Posted by: Paul - Ottawa Bluffs, a few miles east of St. Peter, LeSueur County
on: 2014-06-09 15:24:12

Saw several of these 7 June 2014 at Ottawa Bluffs, pretty bright green in color, not giving up seeds yet.

Posted by: Kenny h - Mower county Shooting Star Trail
on: 2017-06-18 13:15:31

It is growing very scarcely on railroad prairie remnant, East of Rose Creek...cant see seeds yet...I love this grass.

Posted by: Stephan - Pine County near Willow River (Kettle River Township)
on: 2019-07-30 22:40:12

There are a few clumps of this species growing in the sandy soils 2 miles east of town, next to clumps of big bluestem, yarrow, harebell and surrounding jack pines. Highly doubt it was planted deliberately by humans so it must be a true remnant of a once larger population. Seed matured this past week. Pretty neat to find this species so far north of the main prairie ecoregion.

Posted by: Ron Johannsen - Trenton Lake
on: 2020-07-06 09:44:31

Picked some seed today to reseed in recovery prairie fairly sparse.

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