Plants perennial; cespitose to somewhat spreading, sometimes shortly rhizomatous. Culms (1.5)30-90(140) cm. Sheaths open, glabrous or hairy, apices with tufts of hair, these sometimes extending across the collar; ligules of hairs; blades persistent or disarticulating. Inflorescences terminal, racemes or panicles. Spikelets with 3-10 florets; florets bisexual, terminal florets reduced; disarticulation above the glumes and between the florets. Glumes subequal or equal, (2)8-20 mm, usually exceeding the florets, stiffly membranous; calluses with lateral tufts of stiff hairs; lemmas ovate to lanceolate, with 2 complete or incomplete transverse rows of tufts of hairs, sometimes reduced to marginal tufts, 5-9-veined, apices bilobed, lobes usually at least as long as the body, acute, acuminate, or aristate, awned from between the lobes, awns longer than the lobes, twisted, usually geniculate; lodicules 2, fleshy, with hairs or glabrous. Caryopses 1.2-3 mm, obovate to elliptic. Cleistogenes absent. x = 12. Name from the Greek rhytidos, wrinkles, and sperma, seed.

Rytidosperma, as interpreted here and by Edgar and Connor (2000), is a genus of about 45 species that are native to south and southeastern Asia, Australia, New Zealand, and South America. Linder and Verboom (1996) advocated a narrower interpretation of the genus than Edgar and Connor, but acknowledged that there is an almost equally strong case for recognizing a single, large genus, Rytidosperma (p. 607). According to their interpretation, all three species treated here would be placed in Austrodanthonia H.P. Linder (Linder 1997).

Several species of Rytidosperma have been cultivated in research plots or forage trials in North America. The three species treated here have been tried in several states but have escaped cultivation and persisted only in California and Oregon (Weintraub 1953). They have been included in commercial seed mixtures for forage planting in Australia and New Zealand. Other species that have been grown experimentally in both the United States and Canada include Rytidosperma caespitosum (Gaudich.) Connor & Edgar, R. setaceum (R. Br.) Connor & Edgar, and R. tenuius (Steud.) A. Hansen & P. Sunding. They are not known to have escaped or persisted in North America. Rytidosperma caespitosa has now been found as an escape in Alameda and San Mateo counties, California, and R. richardsonii as an escape in Alameda Co., California (Connor, pers. com., 2004).

1.   Rytidosperma penicillatum (Labill.) Connor & Edgar
Hairy Danthonia, Hairy Oatgrass, Poverty Grass

Plants loosely cespitose to somewhat spreading, shortly rhizomatous. Culms 30-90 cm, erect, mostly smooth and glabrous, scabrous-pubescent immediately below the inflorescence, branching extravaginal, the new shoots with scaly cataphylls. Leaves mostly basal, greatly exceeded by the culms, flag leaf blades usually not reaching the inflorescence; sheaths densely hairy or glabrous, with apical tufts of hairs, apical hairs 1-3.5 mm; ligules 0.1-1 mm; blades to 30 cm long and 5 mm wide, flat, folded, or rolled, pubescent or glabrous. Inflorescences 4-10 cm, racemose or paniculate, contracted; pedicels much shorter than the spikelets. Spikelets 9-15(18) mm, longer than the rachis internodes, with 5-10 florets; rachilla internodes 0.2-0.5 mm. Glumes subequal, 8-14(17.5) mm, lanceolate, sometimes with scattered hairs; lower glumes (5)7-9(11)-veined; upper glumes 5-7(9)-veined; calluses 0.5-1.2 mm, longer than wide, with marginal tufts of hairs usually reaching the lower lemma hairs; lemma bodies (2)2.5-4 mm, 9-veined, lower row of hairs continuous or with weak central tufts, hairs of the marginal tufts not or just reaching the upper row of hairs, upper row of hairs composed of 2 marginal tufts, sometimes with 2 additional scanty tufts between, hairs reaching or slightly exceeding the base of the awn; lobes 5-13 mm, aristate; awns (7)9-16 mm; paleas 3-6 mm, exceeding the lemma sinuses, emarginate, intercostal region glabrous or scabrous, margins glabrous or sparsely long-hairy, veins ciliate; anthers 0.4-2.5 mm. Caryopses 1.8-2.5(3) mm long, 0.8-1.1(1.6) mm wide; embryos 0.7-1(1.5) mm; hila 0.4-0.5(0.7) mm. 2n = unknown.

Rytidosperma penicillatum is endemic to Australia and has been introduced to New Zealand as well as North America. Although considered a poor quality forage, it was introduced and grown experimentally in several states under the name Danthonia pilosa R. Br. [= Rytidosperma pilosa (R. Br.) Connor & Edgar]. It has become well-established in northern California and southwestern Oregon, mainly in coastal areas. Since it does well on dry, nutrient depleted soils and competes well with more desirable species, it is considered a troublesome pest.

2.   Rytidosperma biannulare (Zotov) Connor & Edgar

Plants cespitose. Culms 30-85 cm, erect, branching intravaginal. Leaves mostly basal, exceeded by the culms, flag leaf blades usually reaching or exceeding the inflorescences; sheaths mostly glabrous, often purplish distally, with apical tufts of hairs sometimes present, hairs to 5 mm; ligules 0.3-0.5(1) mm; blades 30-40 cm long, to 5 mm wide, usually involute, margins, apices, and sometimes adaxial surfaces scabrous, young blades sparsely pilose, becoming glabrous at maturity. Inflorescences 10-20 cm, narrow, dense panicles; rachises and pedicels scabrous. Spikelets (7)10-15 mm, longer than the rachis internodes, with 6-7 florets; rachilla internodes 0.3-0.5 mm. Glumes subequal, 7.6-11(13.2) mml, lanceolate, subacute; lower glumes 5-7(9)-veined; upper glumes 5-veined; calluses 0.5-0.7 mm, with marginal tufts of hairs reaching the lower lemma hairs; lemma bodies 1.8-2.4(2.8) mm, 7-9-veined, lower and upper rows of hairs dense, hairs of lower rows usually not or only just reaching the upper rows, sometimes ill-defined, hairs of upper rows clearly exceeding the base of the awn but exceeded by the lemma lobes, margins ciliate, other portions of the lemma with short scattered hairs, sometimes glabrous below the upper row of hairs; lobes 3.5-5(8.5) mm, aristate; awns 6-10(12.5) mm; paleas 2.5-4.6 mm, exceeding the lemma sinuses, emarginate, intercostal region sparsely hairy, margins usually long-hairy, veins ciliate; anthers 0.8-1.6 mm. Caryopses 1.2-1.9 mm long, 0.6-0.8 mm wide; embryos0.5-0.8 mm; hila 0.3-0.6 mm. 2n = unknown.

Rytidosperma biannulare is endemic to New Zealand. As early as 1905, it was grown experimentally in several states under the name Danthonia semiannularis (Labill.) R. Br. Although frequently mentioned in literature, only a few specimens document its persistence in Oregon and California.

3. Rytidosperma racemosum (R.Br.) Connor & Edgar

Plants loosely cespitose, shortly rhizomatous. Culms to 90 cm, erect, branching extravaginal, new shoots with scaly cataphylls. Leaves mostly basal, exceeded by or as long as the culms, flag leaf blades usually reaching the inflorescences; sheaths glabrous or with scattered hairs, becoming brownish, with apical tufts of hairs, hairs to 4 mm; ligules 0.2-0.5 mm; blades (5)15-25 cm long, to 2 mm wide, flat or involute, glabrous or pubescent. Inflorescences 5-15 cm, racemose or with a few branches, narrow; rachises and pedicels scabrous. Spikelets (7)10-13(16) mm, sometimes shorter than the rachis internodes, with 6-7(10) florets; rachilla internodes 0.1-0.2 mm. Glumes subequal, (7)8-13(16) mm, lanceolate, subacute, glabrous; lower glumes (5)7-veined; upper glumes 5(7)-veined, sometimes with a few hairs; calluses (0.6)0.9-1.5(2) mm, with marginal tufts of hairs not or barely reaching the lower lemma hairs; lemma bodies 2.5-3.5(4.5) mm, (7)9-veined, lower row of hairs dense, hairs not or just reaching the upper rows, upper row of hairs reaching or slightly exceeding the base of the awn, scanty medial tufts sometimes present; lobes 5-10 mm, abruptly aristate; awns 11-14 mm; paleas 3.5-5 mm, exceeded by the lemma sinuses, emarginate, glabrous or with a few hairs, veins ciliate; anthers 0.3-2 mm. Caryopses 1.7-2.1(2.5) mm long, 0.8-1.1(1.3) mm wide; embryos 0.8-0.9 mm; hila 0.4-0.5 mm. 2n = 24.

Rytidosperma racemosum is endemic to Australia and has been introduced to New Zealand. Grown experimentally in several places in North America, including Berkeley, California, it seems to have become established in only a few places around central California.