Agrostis stolonifera (Creeping Bentgrass)

Plant Info
Also known as: Spreading Bentgrass, Redtop
Genus:Agrostis
Family:Poaceae (Grass)
Life cycle:perennial
Origin:Eurasia, North Africa
Status:
  • Weedy
Habitat:part shade, sun; average to moist disturbed soil; meadows, prairies, fens, shores, river banks, open woods, floodplains, golf courses
Fruiting season:July - September
Plant height:6 to 24 inches
Wetland Indicator Status:GP: FACW MW: FACW NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: irregular Cluster type: panicle

[photo of flowering panicle] Open panicle 1½ to 4 inches long (rarely to 8 inches), longer than wide, lance-elliptic to oblong in outline, the main branches spreading to ascending at flowering time becoming more ascending to erect with maturity, and branchlets along nearly the full length of the branch. Spikelets (flower clusters) are single at branchlet tips, yellowish to purplish at flowering time, up to 3 mm (~1/8 inch) long, and have a single floret.

[close-up of branches] At the base of a spikelet is a pair of bracts (glumes) that are 1-veined, keeled, rough along the keel, pointed at the tip, the upper glume 2 to 3 mm long, the lower glume about as long or slightly shorter. Surrounding the floret is a pair of bracts (lemma and palea), both thin and translucent, the lemma 5-veined, pointed to jagged to somewhat rounded at the tip, 1.4 to 2.3 mm long, shorter than the glumes, and awnless; the palea is half or more as long as the lemma and 2-veined. The thickened base of the floret (callus) is sparsely covered in hairs up to .5 mm long.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of sheath, ligule and node] Leaves are mostly alternate along the stem, up to 4 inches long, 2 to 6 mm (to ~¼ inch) wide, flat, hairless, slightly rough. Sheaths are hairless and smooth. The ligule (membrane where the leaf joins the sheath) is 1 to 6 mm long, the top edge blunt to rounded and lacks a fringe of hairs.

[photo of stolon emerging from a node] Nodes are smooth. Stems are smooth, unbranched, prostrate from the base and rising at a lower node (geniculate) or towards the tip (decumbent), often rooting at the node. Plants can form dense mats from leafy, horizontal, above ground stems (stolons) that may extend to 3 feet or more.

Fruit: Fruit type: seed without plume

[close-up of immature spikelet] Spikelets are purple to straw-colored when mature, the florets dropping away leaving the glumes behind persisting on the stalk. The grain is elliptic, .9 to 1.3 mm long.

Notes:

Creeping Bentgrass, the turf grass of choice for golf courses, is generally considered an introduction from Eurasia but there is some indication populations native to North America may exist. In the wild it is found in a variety of moist habitats from prairies and sedge meadows to sandy shores and river banks, and even calcareous fens, though it can establish itself in nearly any disturbed soils. It is easily confused with the more common Redtop (Agrostis gigantea), which is also colony-forming, has single-flowered spikelets and a palea about half as long as the lemma, but Redtop has rhizomes (underground horizontal stems) rather than stolons, usually a larger panicle (3 to 10 inches long) and the panicle branches remain ascending to spreading even in fruit, where the Creeping Bentgrass panicle rarely exceeds 4 inches (10 cm) long and the branches tend to contract after flowering. In any case, look for stolons.

Of the 5 Agrostis species known to be in Minnesota, A. gigantea and A. stolonifera are the only ones with a distinct palea, where the others have paleas that are minute at best and more often lack them altogether (magnification recommended).

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More photos

Photos by Peter M. Dziuk taken in Ramsey County. Golf course by Easchiff, via Wikimedia Commons, used under CC BY-SA 3.0

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