Poa

Poa pic 1 Poa pic 2

Pictured above: Poa pratensis

This genus is characterized by having leaves with boat-shaped tips. Spikelets are 2 to several flowered, somewhat compressed, with awnless and usually keeled glumes and lemmas. Nerves of the lemma are often pubescent and there is a cobweb of hairs on the callus in our species. Many of the species are quite variable making identification difficult.

There are 18 species in MN; 13 are native.

Common species:
Poa compressa (po' ah come press' ah)

  • Synonyms: None
  • Common names: Canada bluegrass, wire grass
  • Origin and habitat: Introduced from Europe (so why is it called “Canada” bluegrass”?); open, usually dry, areas
  • Identifying characters: This is a rhizomatous perennial with strongly flattened stems with distinct edges and slightly enlarged nodes. Leaf sheaths are also strongly compressed and keeled; ligules are as long as 2 mm. Inflorescences are panicles with paired branches. Spikelets are 3‑6‑flowered and 4‑6 mm long; the lemma has only a small wisp of hairs at the callus.
  • Comments: The distinctly compressed stems and larger spikelets separate this species from the similar looking Kentucky bluegrass (P. pratensis). Lower leaves are shorter than in P. pratensis and plants mature later. When fresh samples are placed side by side, Canada bluegrass generally has a bluer tinge to it. Though introduced the common name came into being in the early part of the century to distinguish this species from Kentucky bluegrass. Shade plants can be very difficult to distinguish from other species of Poa. Considered a valuable forage grass.

Poa palustris (po' ah pah lus' tris)

  • Synonyms: None
  • Common names: swamp bluegrass, waterfowl meadow grass
  • Origin and habitat: Native; wet meadows, streamsides, and other moist habitats
  • Identifying characters: Perennial with loosely clustered stems, often purplish basally. Ligules are up to 4 mm long. Inflorescences are delicate, often nodding panicles with 2-4 flowered spikelets that are 2.6‑4.4 mm long; lemmas are golden-tipped.
  • Comments: More delicate looking than either Canada or Kentucky bluegrass and occupying much moister habitats. However, this too is a variable species. Another native cool-season grass, with most growth occurring in spring or fall.

Poa pratensis (po' ah pray ten' sis)

  • Synonyms: None
  • Common names: june grass, Kentucky bluegrass, spear grass; Lakota: peji blaskaska
  • Origin and habitat: Both native and introduced (from Europe) forms exist but are extremely difficult to tell apart; moist or dry open areas and sometimes in open hardwood forests as well.
  • Identifying characters: Rhizomatous perennial with stems more or less terete. Inflorescences are somewhat pyramidal in shape and have several branches at each node; spikelets are 3-5 mm long.
  • Comments: This species often out-competes other natives after disturbance but the seedlings require more moisture in early spring or late fall since it is also a cool-season grass. It is widely cultivated for sunny lawns and for hay and has been accidentally transported far and wide. Although a rhizomatous grass it easily forms dense sod patches.

Maps

Poa compressaPoa palustris mapPoa Pratensis Map      

Additional species in Minnesota:
Poa alsodes
Poa annua
Poa arida
Poa bulbosa
Poa chaixii
Poa glauca
Poa interior
Poa languida
Poa nemoralis
Poa paludigena
Poa saltuensis
Poa sylvestris
Poa trivialis
Poa wolfii
Poa x tormentuosa

Copyright 2002, A.F. Cholewa, J.F. Bell Museum of Natural History, University of Minnesota / No portion of this guide may be duplicated without written permission of author.