Poa secunda subsp. juncifolia
Poa secunda subsp. juncifolia (Scribn.) Soreng is a perennial grass 3–12 decimetres (0.98–3.94 ft) tall. Its leaf blades are usually less than 1.5 mm wide, firm, tightly folded and rolled inward so that they keep their shape, and often have a bluish-grey (glaucous) bloom. The ligule is 0.5–6 mm long, and the lemmas are 3.5–6 mm long and hairless, or rarely sparsely hairy on the keel. It has about 63 chromosomes (2n = ±63). In California it grows from sagebrush scrub to lower montane forest at 900–3,000 metres (3,000–9,800 ft), often in alkaline depressions. Its range extends beyond California to southern Canada, North Dakota and New Mexico. In saline meadows it hybridises with Kentucky bluegrass (P. pratensis), producing Poa ×limosa.
The subspecies includes three forms that were formerly treated as separate species. Soreng and Gillespie (2018) recognise them as varieties.
- P. secunda var. ampla (big bluegrass)
The largest of the three. The Jepson eFlora describes it as 6–12 decimetres (2.0–3.9 ft) tall with flat, usually glaucous leaf blades, growing in non-alkaline uplands. A USDA NRCS plant guide gives a height of 60–130 centimetres (24–51 in), leaves 1.5–3.5 mm wide, a short, rounded to squared-off ligule, and a panicle 10–18 cm long. It describes the habitat as sagebrush slopes and meadows. The cultivars 'Service' and 'Sherman' belong to this form.
- P. secunda var. juncifolia (alkali bluegrass)
A shorter plant, 30–70 centimetres (12–28 in) tall, with rolled leaves less than 2 mm wide, a short ligule and a panicle 7–15 cm long. Its ligule is truncate (squared off), and it typically grows in alkaline sites such as alkaline meadows.
- P. secunda var. nevadensis (Nevada bluegrass)
Distinguished by a long, pointed (acute) ligule. The NRCS plant guide gives a ligule 1.5 to 6 mm long, a height of up to 100 centimetres (39 in), leaves 1–3 mm wide and a panicle 10–18 cm long. It grows in moist sagebrush areas and foothills. Like var. juncifolia it is often found on alkaline soils, but it also occurs in desert uplands.
Poa secunda subsp. secunda
Poa secunda subsp. secunda has basal tufts of leaves that are usually tiny to medium-sized, less often robust. Its stems (culms) are (10)15–100 cm tall. The panicles are 2–15(20) cm long, usually narrowly lance-shaped to egg-shaped, and contracted at maturity. It has more rounded lemma keels than related species, with hairs between the lemma veins, and a callus that is hairless or has hairs shorter than 0.2 mm.
It generally grows in drier habitats than subsp. juncifolia and is also common in alpine habitats. It ranges from Alaska and the western United States through the Rocky Mountains to the Great Plains, with outlying populations as far east as Ontario, Quebec and Maine. The Flora of North America describes several intergrading forms within it:
- sandbergii: tiny plants that flower in early spring, growing on stony and mossy ground
- scabrella: plants with a rough (scabrous) surface, mainly from west of the Cascade–Sierra Nevada axis
- canbyi: smoother, large plants that extend further east; the cultivar 'Canbar' belongs to this form
- gracillima: slender, sparse plants of generally moist, shady habitats, whose panicles stay open
Soreng and Gillespie (2018) recognise gracillima and scabrella as varieties of subsp. secunda, alongside var. secunda.
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