Jepson eFlora: Key page
Vascular Plants of California
Key to families | Table of families and genera

Key to Poa

View taxon page for Poa

(For a list of species in Poa, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Annual (biennial); anthers generally 0.2–1(1.8) mm; flower generally 

2. Callus glabrous – upper flowers of  often pistillate

3. Spikelet axis generally hidden, terminal  < 1/2 terminal floret; anthers 0.6–1 mm; widespread ..... P. annua

3' Spikelet axis visible, terminal internode > 1/2 terminal floret; anthers 0.2–0.5 mm; especially s CA-FP ..... P. infirma

2' Callus with cobwebby hairs

4. Inflorescence branches   abruptly prow-tipped;  veins hairy ..... P. bigelovii

4' Lower inflorescence branches eventually ; leaf blade abruptly or slightly prow-tipped; lemma short-hairy or surface glabrous or scabrous

5. Lemma glabrous or scabrous; leaf blade abruptly prow-tipped; some spikelet  > 1 mm ..... P. bolanderi

5' Lemma short-hairy; leaf blade , slightly prow-tipped; spikelet internodes generally < 1 mm ..... P. howellii

1' Perennial herb; anthers often > 1.2 mm; flowers occasionally unisexual

6. Rhizomes or stolons present; anthers 1–4 mm

7. Stem and  distinctly keeledwiry; leaf  open nearly to base; inflorescence branches scabrous ..... P. compressa

7' Stem and nodes little or not compressed or wiry; leaf sheath sometimes not open as far; inflorescence branches sometimes smooth

8. Lemma glabrous or minutely scabrous; callus long-cobwebby

9. Sheaths of upper stem leaves open most of their length; leaf blade generally flat; upper surface glabrous or sparsely scabrous; flowers bisexual ..... P. kelloggii

9' Sheaths of upper stem leaves open 1/3–7/10 their length; leaf blade flat, folded, or inrolled, upper surface sometimes finely hairy; flowers generally unisexual

10. Leaf blades thin, soft, generally 0.8–1.5 mm wide, folded, or up to 2.5 mm wide and flat; stem leaves gradually reduced in length upward; lemma (3.2)4.25–5 mm; plants with bisexual flowers or some (rarely all) pistillate or staminate ..... P. diaboli

10' Leaf blades ± thick, firm, generally 1.5–3 mm wide, never flat; stem leaves strongly reduced in length upward; lemma generally 4–7 mm; plants nearly all pistillate- or staminate-flowered ..... P. piperi

8' Lemma hairy at least on keel or callus glabrous

11. Lemma generally < 3.5 mm, lemma and callus smooth, glabrous; stem nodes generally hidden in  tuft; inflorescence < 8 cm, branches appressed, generally smooth; flowers unisexual ..... P. atropurpurea

11' Lemma generally > 3.5 mm or ± scabrous or hairy (if < 4 mm and smooth and glabrous, then some stem nodes well exposed and inflorescence > 8 cm); inflorescence 2–30 cm, branches sometimes ± spreading, sometimes scabrous; flowers bisexual and/or unisexual

12. Leaf blade ± firm, inrolled, upper surface generally densely and finely hairy or scabrous; flowers generally unisexual (except Poa confinis); coastal dunes

13. Lemma <= 4.5 mm, glabrous to sparsely hairy; plant <= 30 cm; inflorescence ± open ..... P. confinis

13' Lemma >> 4.5 mm, glabrous to densely hairy; plant sometimes > 30 cm; inflorescence dense, branches appressed

14. Upper  < 7 mm; lowest lemma <= 7.5 mm; stem very scabrous or coarsely hairy below inflorescence; s NCo, CCo, n ChI ..... P. douglasii

14' Upper glume > 7 mm; lowest lemma > 7.5 mm; stem smooth below inflorescence; n&c NCo ..... P. macrantha

12' Leaf blade generally not firm or inrolled, upper surface glabrous or sparsely soft-hairy; flowers bisexual and/or unisexual; widespread, generally montane, rarely on coastal dunes

15. Sheath of upper stem-leaf closed nearly to top, blade > sheath ..... P. sierrae

15' Sheath of upper stem-leaf open at least 1/4 length, blade <= sheath

16. Callus glabrous (rarely short-cobwebby); lemma glabrous or hairy; flowers often pistillate

17. Lemma generally < 3.5 mm, sometimes glabrous; inflorescence  in outline, short-branched, interrupted, many-flowered; upper stem-leaf blade > 1/5 sheath length; flowers appearing bisexual but anthers generally sterile; tall leafy-stemmed plants of moist, low-elevation meadows ..... P. pratensis × P. secunda (see Poa secunda subsp. juncifolia)

17' Lemma generally > 3.5 mm; inflorescence  to  in outline (otherwise sometimes as above); upper stem-leaf blade sometimes < 1/6 sheath length; flowers generally pistillate (anthers minute);  or tall plants of well drained soils of slopes of forests

18. Stem-leaf blades strongly reduced upward, uppermost < 1/8 sheath length; lemma keel and marginal veins clearly hairy; plant densely cespitose (see 31. for subspecies) ..... P. fendleriana (2)

18' Stem-leaf blades generally longest at middle of stem, uppermost generally > 1/5 sheath length; lemma glabrous to sparsely scabrous or keel and marginal veins sparsely hairy; plant loosely tufted ..... P. wheeleri

16' Callus long-cobwebby (hairs > 1/2 lemma length); lemma keel and marginal veins hairy, glabrous between veins; flowers bisexual (except Poa rhizomata)

19. Sheath generally open > 3/4 length; stolons generally present; stem sometimes branching above base; lemma sometimes hairy only on keel

20. First glume generally 3-veined, not arched; lemma obviously hairy on keel and marginal veins ..... P. palustris (2)

20' First glume 1-veined, ± sickle-shaped; lemma sparsely hairy on keel and rarely on marginal veins ..... P. trivialis (2)

19' Sheath open <= 3/4 length; plant with obvious rhizomes; stem not branching above base

21. Plant often forming a dense sod;   to rounded; inflorescence densely flowered, branches at lower nodes generally 4+ (some may be small); lemma generally < 4 mm; flowers rarely pistillate ..... P. pratensis subsp. pratensis

21' Plant not sod-forming; ligule ; inflorescence sparsely flowered, branches at lower nodes generally 1–2; lemma generally > 4 mm; flowers occasionally pistillate ..... P. rhizomata

6' Rhizomes and stolons 0; anthers 0.2–4.5 mm

22. Stem base ± bulbous; most  producing leafy  or not ..... P. bulbosa

23. Spikelets not producing leafy bulblets ..... [subsp. bulbosa]]

23' Spikelets generally producing leafy bulblets ..... subsp. vivipara

22' Stem base not bulbous;  not mostly replaced by bulblets

24. Callus cobwebby; lemma glabrous ..... P. abbreviata subsp. marshii

24' Callus glabrous, with a ring of short hairs, or cobbwebby; if callus cobbwebby then lemma also hairy to some degree

25. Callus ± cobwebby; lemma hairy on keel and generally on marginal veins but not between veins

26. Inflorescence < 10 cm, sparse or dense; plant densely cespitose

27. Plant << 20 cm; sheaths open > 3/4 length; flower generally bisexual, anthers generally 0.7–1.2 mm ..... P. abbreviata subsp. pattersonii

27' Plant > 20 cm; sheaths open <= 1/2 length; flowers pistillate, anthers vestigial ..... P. cusickii subsp. purpurascens (2)

26' Inflorescence generally > 10 cm or open; plant loosely cespitose

28. Lower glume generally 3-veined; sheaths open 3/4 length or more

29. Ligule of upper stem-leaf truncate, generally < 0.5 mm ..... P. nemoralis

29' Ligule of upper stem-leaf acute to rounded, generally > 1 mm ..... P. palustris (2)

28' Lower glume generally 1-veined; sheaths open to 3/4 length

30. Anthers <= 1 mm; inflorescence branches with flowers in top 1/3; high montane to alpine ..... P. leptocoma subsp. leptocoma

30' Anthers > 1.3 mm; some inflorescence branches with flowers from mid-length; low elevation ..... P. trivialis (2)

25' Callus glabrous or not cobwebby (ring of short callus hairs present in some Poa secunda, Poa unilateralis); lemma often hairy between veins

31. Lemma obviously hairy at least on keel and marginal veins; flowers unisexual; sheath open ± 1/3 length; uppermost stem-leaf blade firm, often highly reduced; callus glabrous ..... P. fendleriana (2)

32. Ligule 0.2–1.5 mm, margin scabrous or short-ciliate ..... subsp. fendleriana

32' Ligule 1–18 mm, margins smooth, glabrous ..... subsp. longiligula

31' Lemma often glabrous (if obviously hairy on keel and marginal veins or between, then flowers bisexual, sheaths open > 3/4 or < 1/2 length; uppermost stem-leaf blade often thin and withering or not highly reduced); callus sometimes with a crown of short hairs

33. Spikelet lanceolate to narrowly ovate in outline, little compressed; lemma weakly keeled; sheath open > 3/4 length; flowers bisexual

34. Inflorescence branches widely spreading in flower and fruit, generally densely scabrous; ligule 0.5–1.5(2.5) mm, truncate to  (rarely acute), scabrous; plant delicate, spring-active; often on serpentine ..... P. tenerrima

34' Inflorescence branches generally  to appressed in fruit (generally spreading only in flower), ± scabrous; plant generally more robust, or summer-active, of high elevation, or delicate with branches ± smooth and ligules longer and ± smooth; on various substrates ..... P. secunda

35. Lemma glabrous (sometimes scabrous, rarely sparsely short-hairy); ligule of sterile shoots and often stem < 2 mm, ± truncate, scabrous; leaf blade ± firm, retaining shape; inflorescence branches appressed ..... subsp. juncifolia

35' Lemma ± evenly short-hairy on keel and sides across base; ligule of sterile shoots and stem generally > 2 mm, acute or , smooth or sparsely scabrous; leaf blade generally ± soft, soon withering; inflorescence branches appressed or spreading ..... subsp. secunda

33' Spikelet ± ovate in outline, obviously compressed; lemma obviously keeled to base; sheaths sometimes open < 3/4 length; flowers sometimes unisexual

36. Uppermost sheath open <= 1/2 length; lemma > 4.5 mm, sparsely hairy on keel, base, and sometimes marginal veins; flowers pistillate ..... P. cusickii subsp. purpurascens (2)

36' Uppermost sheath generally open > 1/2 length; lemma generally < 4.5 mm or glabrous (if hairy, sheath open > 3/4 length, flowers bisexual)

37. Lemma obviously hairy, < 3.6 mm; subalpine or higher ..... P. glauca subsp. rupicola

37' Lemma often glabrous, length various (if lemma obviously hairy, plant coastal)

38. Sheath open ± 9/10 length; flowers bisexual; low salty places; coast or w CA

39. Inflorescence branches ascending, very scabrous, with spikelets only in top 1/2; near hot springs, NCoRO, Napa Co. ..... P. napensis

39' Inflorescence branches appressed, smooth to sparsely scabrous, with spikelets from near base; sea bluffs, NCo, n&c CCo ..... P. unilateralis subsp. unilateralis

38' Sheath open < 9/10 length; flowers sometimes unisexual; generally ± salt-free places; montane or GB

40. Plant generally < 1 dm; longest anthers 0.2–2 mm; upper glume generally >= first lemma; lemma sometimes sparsely short-hairy; flowers bisexual

41. Leaf firm; lemma 3–5 mm; anthers 0.7–1.8 mm ..... P. keckii

41' Leaf soft; lemma <= 3 mm; anthers 0.2–0.7 mm ..... P. lettermanii

40' Plant generally 1–7 dm; longest fertile anthers 2–4.5 mm; upper glume generally < first lemma; lemma glabrous; flowers sometimes unisexual

42. Ligule of uppermost leaf of sterile stems 2.5–6 mm, acute, smooth; lemma <= 5.5 mm; lowest true leaves lacking blades; flowers bisexual or pistillate (rarely staminate); SNH ..... P. stebbinsii

42' Ligule of uppermost leaf of sterile stems generally < 2 mm (if 2–3 mm, lemma > 5.5 mm), truncate to obtuse, scabrous; lowest true leaves sometimes with blades; all flowers generally unisexual; more widespread

43. Plant generally < 30 cm, base often ; leaf blades of sterile stems generally > 1.5 mm wide, arched, their ligules sometimes > 2 mm; upper glume sometimes = first lemma; KR, CaRH, n SNH ..... P. pringlei

43' Plant 25–70 cm, base rarely decumbent; leaf blades of sterile stems < 1.5 mm wide, , their ligules < 2 mm; upper glume obviously < first lemma; widespread, especially GB ..... P. cusickii (in part)

44. Basal tuft of leaves sparse; inflorescence branches ± smooth; 1–2 stem nodes exposed; flowers pistillate ..... subsp. epilis

44' Basal tuft of leaves dense; inflorescence branches obviously scabrous; 0–1 stem nodes exposed; flowers sometimes staminate (rarely bisexual)

45. Inflorescence branches slender, longest generally > 17 mm; moist sagebrush to dry montane slopes ..... subsp. cusickii

45' Inflorescence branches stout, longest generally < 15 mm; dry ± alpine ridges – uncommon in California ..... subsp. pallida


Please use this Google Form for Contact/Feedback

Citation for the whole project: Jepson Flora Project (eds.) . Jepson eFlora, [accessed on ]

Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on .

We encourage links to these pages, but the content may not be downloaded for reposting, repackaging, redistributing, or sale in any form, without written permission from The Jepson Herbarium.