porcupine grass

(Hesperostipa spartea)

Conservation Status
porcupine grass
Photo by Nancy Falkum
  IUCN Red List

not listed

     
  NatureServe

N5? - Secure

SNR - Unranked

     
  Minnesota

not listed

     
           
           
           
           
           
           
 
Description
 
 

Porcupine grass is a tall, cool season (C3) bunchgrass. It occurs in North America from Ontario to British Columbia south to Alabama and New Mexico. It is most common in the central and Great Lakes regions. It is very common in Minnesota. It is found as bunches of individual plants in dry to moderately dry prairies, on roadsides, and in railroad rights-of-way. It grows most actively in the spring and early summer, usually under full sun in sandy or gravelly soil, but also in loamy soil and in light shade.

Porcupine grass has deep fibrous roots. Bunches are 2½ to 3½ tall and can have a foliage spread of 3 to 6 in diameter.

The stems (culms) are round, hollow, and pale green. They can be 18 to 57 (45 to 145 cm) long but are usually no more than 36 (90 cm) long. They are erect at first but soon lean over due to the weight of the developing spikelets. They do not branch at the upper nodes. They are mostly hairless but often have lines of minute hairs at the nodes. These may not be visible without strong (20x) magnification.

Both basal leaves and a few stem leaves are produced. Stem leaves are few and alternate. The leaf blade is linear to lance-shaped. It can be 6 to 26 (15 to 65 cm) long and 116 to ¼ (2 to 6 mm) wide, but is usually no more than 18 (45 cm) long. It is narrowed but not twisted at the base, and tapers to a long fine point at the tip. The veins are parallel, the midvein is not thickened, and there are no evident cross-veins. The upper surface is rough, hairy, and conspicuously ridged. The underside is hairless and sometimes roughened. The margins are flat but often curl tightly inward in response to dry conditions. The lower part of the leaf surrounding the stem (sheath) is open for all or most of its length. There is usually a fringe of hairs on the lower margin though this may be hard to see. It is otherwise hairless. There are no ear-like extensions (auricles) at the top of the sheath. The area on the outer side where the blade meets the sheath (collar) does not have tufts of hairs on the sides. The appendage on the inner side at the junction of the blade and the sheath (ligule) is white and membranous.The ligule on lower leaves is 132to (0.3 to 3.0 mm) long, stiff, and straight across to rounded. It usually does not appear torn (lacerate). The ligule on upper leaves is to ¼ (3.0 to 7.5 mm) long, thin, pointed, and often lacerate. Basal leaves are similar to stem leaves but are a little longer. Stems and stem leaves turn brown in the fall, but basal leaves remain green as other grasses turn brown.

The inflorescence is a 4 to 10 (10 to 25 cm) long, narrow, few-branched arrangement (panicle) of spikelets at the end of the stem. Sometimes 2 or 3 additional panicles develop at the uppermost stem nodes. Each branch of the panicle is erect and slender, and bears 1 or 2 spikelets. The panicle leans to one side due to the weight of the developing spikelets.

Each spikelet has one modified flower (floret) with 2 bracts (glumes) at the base. Each glume is to 1¾ (2 to 45 mm) long, is linear lance-shaped, tapers to a long-pointed or hair-like tip, and has 5 or 7 nerves. The outer surface is hairless. The glumes are longer than on other needle grasses in Minnesota. They remain on the plant long after seed dispersal, which is helpful in identifying this plant in late summer and fall.

The floret consists of an outer bract (lemma), an inner bract (palea), and a flower with both male and female parts (perfect). The body of the lemma is brown, not shiny, hard, linear, tapered at the tip to a very long awn, and to 1 (15 to 25 mm) long not including the awn. The outer surface is densely hairy on the margins and in lines on the lower part, hairless on the upper part. The hairs are brown at maturity. The awn is 3½ to 7½ (90 to 190 mm) long. It is bent at a sharp angle twice near the middle but it is not jointed. The central segment is usually to 1316 (15 to 30 mm) long. The lower two segments are spirally coiled when dry, the terminal segment is straight, not twisted. Following seed dispersal the awns coil and uncoil as moisture conditions change, screwing the fruit into the ground. The hairs near the tip face backward and prevent the fruit from backing out of the soil. The palea is flat, pinched or prow-like at the tip, and equal in length to the lemma. It is leathery, hairy, and has two veins. The veins terminate at the tip of the palea.

 
     
 

Height

 
 

18 to 57 (45 to 145 cm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Dry to moderate moisture. Prairies, roadsides, and railroads. Full sun.

 
     
 
Biology
 
 

Flowering

 
 

May to July

 
     
 

Pests and Diseases

 
 

 

 
     
 

Toxicity

 
 

The sharp awns can cause injury to the eyes, nose, mouth, and intestines of livestock

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

2, 3, 4, 5, 7, 24, 28, 29, 30.

 
  1/1/2022      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

Very common in Minnesota

 
         
 
Taxonomy
 
  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Liliopsida (monocots)  
 

Order

Poales (grasses, sedges, cattails, and allies)  
 

Family

Poaceae (grasses)  
  No Rank BOP clade  
  Subfamily Pooideae  
  Supertribe Stipodae  
 

Tribe

Stipeae (needlegrasses and allies)  
 

Genus

Hesperostipa  
       
 

This species was formerly in the genus Stipa. In 1993 all North American species were excluded from that genus. Four species were transferred to the new genus Hesperostipa based on the hard tip of the palea and the pattern of the veins on its surface. Hespero is from Classical Greek and means “western”.

 
       
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

Stipa robusta

Stipa spartea

Stipa spartea var. spartea

 
       
 

Common Names

 
 

big needlegrass

porcupine grass

porcupinegrass

porcupine needlegrass

short-awn porcupine grass

western porcupine grass

 

 

 

 

 

 

 

 

 

Glossary

Bract

Modified leaf at the base of a flower stalk, flower cluster, or inflorescence.

 

Collar

In grasses: The area on the back of a grass leaf at the junction of the sheath and the blade. In moths: the array of scales on the dorsal part of the prothorax.

 

Culm

The hollow or pithy stem of a grass, sedge, or rush.

 

Floret

An individual flower in a dense cluster of flowers; or a modified flower in the flower head in the Asteraceae family and some other families. In grasses, the modified flower in a spikelet of Poaceae and some Cyperaceae with its lemma and palea.

 

Glume

A chaffy, empty, sterile bract at the base of a grass spikelet. Glumes usually occur in pairs, but occasionally only one is present.

 

Lemma

The outer, lowermost of the pair of bracts at the base of the grass floret; it ensheathes the palea.

 

Ligule

In grasses and sedges, a membranous appendage at the junction of the leaf and the leaf sheath, sometimes no more than a fringe of hairs. In flowering plants, the flat, strap-shaped, petal-like portion of the corolla of a ray floret.

 

Linear

Long, straight, and narrow, with more or less parallel sides, like a blade of grass.

 

Palea

The inner, uppermost of the pair of bracts at the base of the grass floret.

 

Panicle

A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.

 

Sheath

The lower part of the leaf that surrounds the stem.

 

Spikelet

In flowering plants, a small spike. In grasses and sedges, the basic unit of inflorescence. In grasses, composed of usually two glumes and one or more florets. In sedges, a single flower and its single associated scale.

 

 

 

 
 
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Nancy Falkum

 
 

Landscape Looking West Minnesota River bluffs in background

 
    porcupine grass      
           
 
MinnesotaSeasons.com Photos
 
 

 

 
           

 

Camera

     
 
Slideshows
 
Stipa (Hesperostipa) spartea - porcupinegrass
Matt Lavin
  Stipa (Hesperostipa) spartea - porcupinegrass  
 
About

A native perennial bunchgrass that is very similar to Stipa comata except much more robust in that the florets are 15-25 mm long and covered with brownish hairs, the lemma awns are 9-19 cm long, and the glumes are 25-45 mm long. Ecologically similar to Stipa comata in thriving on both undisturbed and disturbed steppe and prairie.

 
Hesperostipa spartea
Corey Raimond
  Hesperostipa spartea  

 

slideshow

       
 
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Other Videos
 
  Hesperostipa spartea (Porcupine grass)
Botany and Beer
 
   
 
About

Jul 28, 2021

One of the most charismatic and unforgettable prairie/savanna grasses of the Midwest.

 
  Hesperostipa spartea awns
Josh Drizin
 
   
 
About

Jul 22, 2010

Hesperostipa awns spartea curling like crazy when the humidity drops. Time-lapsed at 5 seconds between each frame

 

 

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Created: 1/1/2022

Last Updated:

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