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• Poaceae Group 4
• Poa
• Poa pratensis

Poa pratensis — Kentucky blue grass

Facts

Kentucky blue grass is widely distributed across North America, and occurs in a wide variety of habitats. Cultivated strains have been developed for lawns and pasture, and these may escape. There are four subspecies found in New England: one (Poa pratensis ssp. alpigena) is confined to Mt. Washington, Coos County, New Hampshire, and is a rare native; another (P. pratensis ssp. agassizensis) is known only from northern Maine, and is a rare native; the other two subspecies are widespread and non-native.

Habitat

Alpine or subalpine zones, anthropogenic (man-made or disturbed habitats), meadows and fields, mountain summits and plateaus, shores of rivers or lakes

Characteristics

• Flowers

  Anther length

  1.2–2 mm

  Anther number

  3

  Awn on glume

  the glume has no awn

  Bristles below spikelets

  no

  Floret lower bract texture

  the lemma is thin and flexible

  Floret number

  2–5

  Floret types within spikelet

  all the florets within a spikelet are similar

  Glume awn length

  0 mm

  Glume keel

  the glume keels are rough or hairy

  Glume relative length

  neither glume is quite as long as all of the florets

  Glume shape

  the glume is V-shaped in cross-section

  Glume veins

  • 1
  • 3

  Glumes per spikelet

  2

  Inflorescence arrangement

  the spikelets are uniform

  Inflorescence axis orientation

  the inflorescence axis is straight

  Inflorescence branch length

  1–6 cm

  Inflorescence branch roughness

  • the inflorescence branches are smooth or only slightly rough
  • the inflorescence branches are somewhat to very rough

  Inflorescence branches

  the flowers are attached to branches rather than to the main axis of the inflorescence

  Inflorescence branches coming off the lowest stem node

  2–5

  Inflorescence crowding

  • the panicle is somewhat to very congested (crowded), and the branches may not be clearly seen without close inspection
  • the panicle is somewhat to very spread out, with clearly-evident branches

  Inflorescence length

  30–200 mm

  Inflorescence length to width ratio

  1.5–2.86

  Inflorescence type (general)

  the spikelets are borne on stalks or on branches

  Inflorescence type (specific)

  the inflorescence is branched, and the branches do NOT both grow from the same side of the plant AND look like spikes

  Inflorescence width

  20–70 mm

  Inforescence position

  the spikelets are mainly carried at the end of the stem

  Lemma awn base

  NA

  Lemma awn coiled

  NA

  Lemma awn length

  0 mm

  Lemma awn number

  the lemma has no awn

  Lemma awn orientation

  NA

  Lemma base hairs

  the lemma has hairs at the base

  Lemma cross-section

  the lemma is V-shaped if you cut across the midpoint

  Lemma hairs

  the lemma is hairless between the veins

  Lemma keel hairs

  the keel of the lemma is rough, or has fine hairs

  Lemma marginal vein hairs

  the marginal vein of the lemma has fine hairs on it

  Lemma surface

  • the surface of the lemma has wrinkles that are oriented across the lemma
  • the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)

  Lemma tip

  the lemma tip is a simple point, with or without an awn (long narrow extension ending in a point)

  Lemma tip shape

  the lemma tip tapers to a narrow point (it may or may not also have an awn or teeth at the tip)

  Lemma vein number

  5

  Lower glume length

  1.5–4.5 mm

  Lower glume relative length

  the lower glume is nearly as long, or as long as, the upper glume

  One or more florets

  there is more than one floret per spikelet

  Palea length

  2–3 mm

  Palea relative length

  palea is one half to fully as long as lemma

  Reproductive system

  all the flowers on the plant have both carpels and stamens (synoecious)

  Spikelet axis tip

  there is an extension of the spikelet axis beyond the tip of the spikelet

  Spikelet disintegration

  the spikelet breaks off above the glumes, so that after the florets fall off, the glumes remain

  Spikelet length

  3.5–7 mm

  Spikelet number per node

  0

  Spikelet pedicel

  the spikelets have pedicels

  Spikelet pedicel length

  0.2–2 mm

  Spikelet position

  the spikelets emerge mainly from the upper halves of the inflorescence branches

  Spikelet shape

  the spikelets are lanceolate (lance-shaped, widest below the middle and tapering narrowly to the ends) in profile

  Spikelet width

  1.5–3 mm

  Spikelets per panicle branch

  5–15

  Spikelets spiny

  the spikelets do not appear spiny

  Tip of glume

  the tip of the glume is not divided (though it may have an awn on it)

  Upper glume length

  2–5 mm

  Upper glume relative length

  the upper glume is more than one half as long as the lowest lemma

  Upper glume shape

  the upper glume is widest at or below the middle

• Fruits or seeds

  Seed length

  1.5–2 mm

• Growth form

  Horizontal rooting stem

  no

  Lifespan

  the plant lives more than two years

  Rhizomes

  yes

  Roots

  the plant has rhizomes (horizontal underground stem with roots growing from it)

• Leaves

  Basal leaves

  the plant has large or prominent tufts of leaves at the base of the flowering stem

  Leaf auricles

  the leaves do not have auricles

  Leaf basal lobe hairy

  NA

  Leaf blade base

  the leaf blade is rounded in to a narrower base, or the blade cuts in abruptly to the narrower base

  Leaf blade cross-section

  • the leaf blade is clearly folded or rolled inwards
  • the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards

  Leaf blade hairs

  the leaf blade is hairless, but it may have tiny prickles that give it a sand-papery feel

  Leaf blade length

  5–30 cm

  Leaf blade texture

  • the leaf blade is rough and sandpapery
  • the leaf blade is smooth, or it may have soft hairs

  Leaf blade width

  0.4–4.5 mm

  Leaf ligule length

  0.9–3.1 mm

  Leaf ligule type

  • the leaf ligule is in the form of a membrane
  • the leaf ligule is in the form of a membrane with fine hairs

  Leaf margin glands

  there are no glands along the edges of the leaf blade

  Leaf sheath closed around stem

  the margins of the leaf sheath are overlapping and not fused together except in the basal half (or less)

  Leaf sheath color and persistence

  the leaf sheathes are off-white to light-brown and mostly persist in older leaves

  Leaf sheath hair type

  there are no hairs on the surface of the leaf sheath

  Leaf sheath hairs

  • there are hairs on the surface of the leaf sheath
  • there are no hairs on the surface of the leaf sheath

  Orientation of topmost leaf

  the flag leaf is held upright, or at less than a 45 degree angle out from the stem

• Place

  Habitat

  • terrestrial
  • wetlands

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • alpine or subalpine zones
  • man-made or disturbed habitats
  • meadows or fields
  • mountain summits and plateaus
  • shores of rivers or lakes

• Stem, shoot, branch

  Hairs at nodes

  the stem nodes are hairless or they have very sparse hairs

  Plant height

  8–100 cm

  Stem hairs

  the stem is nearly to completely hairless

  Stem node number

  2–4

  Stem orientation

  • the stems are upright
  • the stems trail at the base, but turn upwards at the tips

  Stem spacing

  • the stems grow close together in compact clusters or tufts
  • the stems grow singly or a few together (they may form diffuse colonies)

  Stem thickness at base

  2–3 mm

Wetland status

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae