Description: This native perennial grass forms low basal leaves and small tufts of leafy culms about 2½–3½' tall. The culms are mostly erect, but they usually lean over to one side after the blooming period because of the heavy weight of the developing grains and awns. The culms are terete, glabrous, and initially pale green; after the blooming period, they become tan or straw-colored. The blades of the alternate leaves are up to 12" long and ¼" across; they are pale to medium green and flat or rolled upward along the margins. The leaf sheaths are longitudinally veined and initially pale to medium green; after the blooming period, they become yellowish green to pale brown. Both the blades and sheaths lack significant hairs. The basal leaves are similar to the alternate leaves, except their blades are a little longer than the blades of the latter. The ligules are white-membranous.
Each culm terminates in a little-branched
panicle of spikelets about 6-10" long. Each lateral branch of the panicle bears
1-2 spikelets. A spikelet consists of 2 glumes and a single awned lemma that
encloses the floret. The glumes are about 1¼–1½" long,
linear-lanceolate in shape, and white-membranous. Each glume has a convex outer
surface with 5-7 longitudinal veins. The lemma is about ¾–1" long
(excluding its awn), linear-lanceolate in shape, and brown; it wraps around the
developing grain of the floret. The outer surface of the lemma is mostly
pubescent, although it becomes hairy toward the bottom. The sharp awn of the
lemma is 4-8" long. This awn is initially straight, but it later bends at a
sharp angle (usually at two locations); the
lower portion of the awn is spirally twisted. The
blooming period occurs from late spring to early summer. The florets are
cross-pollinated by the wind. When the grains become mature, the awned lemmas
detach from the spikelets and fall to the ground, while the glumes remain
attached to the branches of the panicle. Over time, the twisting motion of the
contorted awn drills the lemma with its grain into the ground. The root system
consists of a tuft of deep fibrous roots.
Cultivation: The preference is full sun, mesic to
dry conditions, and sandy or gravelly soil. However, fertile loamy soil and a
little shade are also tolerated. Most growth and development occurs during the
spring and early summer; this is a cool-season grass with a C3 metabolism. The
basal leaves are semi-evergreen.
Range &
Habitat: Porcupine Grass is occasional in the northern half of
Illinois and largely absent from the southern half of the state (see
Distribution Map). Habitats include mesic to dry black soil prairies, sand
prairies, gravel prairies, dolomite prairies, hill prairies, upland savannas
and sandy savannas, pastures, roadsides, and areas along railroads. Porcupine
Grass is a typical prairie grass of the northern plains (both tall-grass and
mixed-grass prairie).
Faunal
Associations: The leafhopper Commellus colon is a specialist
feeder of Porcupine Grass. Because this grass is often found in dry open
prairie, its foliage is occasionally eaten by various species of grasshoppers
that prefer this kind of habitat. The Franklin Ground Squirrel and
Thirteen-Lined Ground Squirrel eat the long grains of Porcupine Grass and
similar grasses (collectively known as Needle Grasses). Young foliage is
palatable to various hoofed mammalian herbivores, including horses, cattle, and
bison. However, the long awns of mature plants can injure the mouthparts of
these animals or pierce their skin. The awns can become caught in the wool of
sheep and transported considerable distances as a result.
Photographic
Location: The Shortline Prairie in Champaign County,
Illinois.
Comments: Porcupine Grass has the longest awned lemmas (with enclosed grains) of any grass species in Illinois. After releasing their awned lemmas to the ground, the culms of this grass become more erect and assume a somewhat ghostly appearance because of the long membranous-white glumes. The only other grass species that is similar, Heterostipa comata (Needle-and-Thread), is slightly smaller in stature and it has shorter glumes (up to 1"), shorter lemmas (up to ½"), and shorter awns (4-6") . In the more western and drier areas of the northern plains, this species largely replaces Porcupine Grass. While Needle-and-Thread has been found in northern Illinois, it is a rare plant. Older scientific names of Needle-and-Thread and Porcupine Grass are Stipa comata and Stipa spartea, respectively.