Jepson eFlora
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Key to Agrostis

View taxon page for Agrostis

1. Rhizomes or stolons well developed, clearly present; perennial herb

2. Plant from stolons

3. Ligule 0.5–2 mm, generally wider than long; stolons < 5 cm; inflorescence widely ovate in outline, 1° branches mostly spreading, spikelets not crowded ..... A. capillaris (3)

3' Ligule 2–5 mm, longer than wide; stolons 5–100 cm; inflorescence elliptic to lanceolate in outline, 1° branches generally all ascending, spikelets overlapping, crowded ..... A. stolonifera

2' Plant from rhizomes

4. Floret callus hairs 1.5–2 mm, generally > 1/2 lemma; ligule 4–7 mm ..... A. hallii (3)

4' Floret callus hairs generally minute, sparse, or 0; ligule generally < 3 mm (except Agrostis gigantea)

5. Palea 0 or minute, << lemma

6. Proximal leaf blade 1–6 mm wide; lemma tip minutely toothed; rhizome < 10 cm; anthers 0.7–1.8 mm ..... A. pallens (3)

6' Proximal leaf blade < 1 mm wide; lemma tip ± acute; rhizome < 5 cm; anthers 0.5–0.7 mm ..... A. variabilis (3)

5' Palea well developed, ± 1/2 to slightly < lemma

7. Inflorescence ± oblong in outline, ± open, branches generally ascending to erect; montane to alpine, 1300–3500 m ..... A. humilis (2)

7' Inflorescence generally ovate in outline, open, most branches spreading; open, generally disturbed places, < 2000 m

8. Rhizomes < 5 cm, slender, not clearly scaly; ligule generally wider than long; inflorescence branches with spikelets on distal 1/2 ..... A. capillaris (3)

8' Rhizomes < 25 cm, ± thick, ± scaly; ligule longer than wide; inflorescence branches with spikelets ± throughout ..... A. gigantea (2)

1' Rhizomes or stolons 0; annual or perennial herb

9. Lemma awned from back or near tip

10. Inflorescence open, generally oblong to ovate in outline; spikelets not crowded, inflorescence axes clearly visible

11. Inflorescence generally oblong to lanceolate in outline, 1° branches generally ascending

12. Lemma awned below middle; anthers 1–1.5 mm; proximal leaf sheaths finely tomentose ..... A. hooveri

12' Lemma awned at or above middle; anthers <= 0.8 mm; proximal leaf sheaths generally glabrous

13. Proximal inflorescence branches 1–2 cm; awn < 3.5 mm, straight to bent; palea < 1/3 lemma; anthers 0.3–0.6 mm ..... A. exarata (3)

13' Proximal inflorescence branches 2–6 cm; lemma awn < 2 mm, straight; palea 1/5–1/4 lemma; anthers 0.6–0.8 mm ..... A. oregonensis (2)

11' Inflorescence generally ovate in outline, proximal-most 1° branches spreading, distal branches generally ascending

14. Lemma back puberulent below middle; floret axis prolonged beyond floret ± 1 mm, short-hairy-tufted; palea > 1 mm ..... A. avenacea

14' Lemma back glabrous or fine-scabrous; floret axis not prolonged beyond lemma; palea 0 or minute

15. Lemma generally awned near tip, awn 3–10 mm, wavy; callus hairs < 0.6 mm, dense; anther 1, persistent in fruit; annual ..... A. elliottiana

15' Lemma awned below middle, awn < 2 mm, ± straight; callus hairs << lemma, sparse; anthers 3, deciduous; perennial herb ..... A. scabra (2)

10' Inflorescence dense, generally cylindric; spikelets crowded, overlapping, inflorescence axes not clearly visible

16. 1° inflorescence branches generally > 0.5 cm, often evident at base (except Agrostis blasdalei)

17. Leaf blade generally < 1 mm wide, ± inrolled; floret callus glabrous; inflorescence base often partly enclosed by sheath of distal-most leaf; anthers 1–2 mm ..... A. blasdalei (2)

17' Leaf blade generally 2–10 mm wide, flat; floret callus minutely hairy; inflorescence base not partly enclosed by sheath of distal-most leaf; anthers ± 0.5 mm

18. Back of glume fine-scabrous throughout; palea 0.5–0.7 mm; ligule 1.5–2 mm ..... A. densiflora (3)

18' Back of glume ± glabrous (keel fine-scabrous); palea ± 0.3 mm; ligule 2.5–4 mm ..... A. exarata (3)

16' 1° inflorescence branches generally < 0.5 cm (< 1.5 cm in Agrostis microphylla), obscured by densely clustered spikelets

19. Lemma teeth 4, two < 1 mm, other two 1–1.5 mm; lemma awned below middle; callus densely short-hairy ..... A. tandilensis

19' Lemma teeth 0 or 2, equal; lemma awned at or above middle; callus generally sparsely hairy, hairs minute

20. Lemma awned above middle, awn < 3.5 mm, straight; glume tips acute; perennial herb ..... A. densiflora (3)

20' Lemma awned ± at middle, awn 3.5–10 mm, generally bent; glume tips narrowly acuminate to awn-like; annual

21. Lemma 2–4 mm, awn 8–10 mm ..... A. hendersonii

21' Lemma 1.5–2 mm, awn 3.5–8 mm ..... A. microphylla

9' Lemma awnless (occasionally short-awned near tip in Agrostis capillaris, from near middle in Agrostis pallens)

22. Spikelets crowded and often overlapping on same branch, spikelet stalks and 2° axes not clearly visible

23. Palea 1/3–2/3 lemma

24. Lf blade 2–10 mm wide; lemma 1.5–2 mm; floret callus minutely hairy; coastal bluffs ..... A. densiflora (3)

24' Lf blade 0.3–1.5 mm wide; lemma 1.1–1.5 mm; floret callus glabrous; vernal pools ..... A. lacuna-vernalis

23' Palea 0 or < 1/3 lemma

25. Leaf blade generally < 1 mm wide, generally inrolled or folded

26. Anthers 1–2 mm; inflorescence branches generally < 0.5 cm; coastal habitats < 100 m ..... A. blasdalei (2)

26' Anthers 0.5–0.7 mm; inflorescence branches 0.5–1.5 cm; inland mtns, 1600–4000 m ..... A. variabilis (3)

25' Leaf blade generally 2–7 mm wide, generally flat

27. Floret callus hairs 1.5–2 mm, generally slightly > 1/2 lemma ..... A. hallii (3)

27' Floret callus hairs 0 or < 0.5 mm, < 1/2 lemma

28. Proximal inflorescence branches 1–2 cm; anthers 0.3–0.6 mm ..... A. exarata (3)

28' Proximal inflorescence branches 2–5 cm; anthers 0.7–1.8 mm ..... A. pallens (3)

22' Spikelets not crowded, generally well spaced on same branch, axes generally clearly visible

29. 1° inflorescence axes branched 1–2 × above middle, spikelets 0 on proximal 1/2

30. Proximal leaf blades 2–4 mm wide; glumes 2–3 mm; palea 1/5–1/4 lemma; anthers 0.6–0.8 mm ..... A. oregonensis (2)

30' Proximal leaf blades 0.5–3 mm wide; glumes 1.5–3 mm; palea 0 or minute, << lemma; anthers <= 0.7 mm

31. Leaves basal and cauline; inflorescence ± 2 × longer than wide; 1° axes ± stiff ..... A. idahoensis

31' Leaves mostly basal; inflorescence ± long as wide; 1° axes flexible, proximal ± arched ..... A. scabra (2)

29' 1° inflorescence axes branched 1–2 × from base upwards, spikelets distributed throughout

32. Floret callus hairs 1.5–2 mm, generally slightly > 1/2 lemma; anthers >= 1.5 mm ..... A. hallii (3)

32' Floret callus glabrous or hairs minute, << lemma; anthers generally < 1.5 mm (except some Agrostis pallens)

33. Palea 0 or minute, << lemma

34. Leaf blade 1–6 mm wide; plants generally 10–70 cm; anthers 0.7–1.8 mm ..... A. pallens (3)

34' Leaf blade generally < 1 mm wide; plants 4–30 cm; anthers 0.5–0.7 mm ..... A. variabilis (3)

33' Palea >= 1/2 lemma

35. Inflorescence branches ascending to erect; anthers < 1 mm; moist to ± dry areas, generally > 1500 m ..... A. humilis (2)

35' Inflorescence branches spreading to ascending; anthers 0.8–1.5 mm; disturbed areas, generally < 1500 m

36. Ligule 0.5–2 mm, generally wider than long; inflorescence branches with spikelets on distal 1/2 ..... A. capillaris (3)

36' Ligule 2–6 mm, longer than wide; inflorescence branches with spikelets ± throughout ..... A. gigantea (2)

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