Plants perennial, rhizomatous, mat-forming. Culms 5-40 cm tall. Ligules to 0.3 mm, of hairs, often with longer hairs at the base of each blade immediately behind the ligule; blades usually glabrous abaxially, sometimes with a ciliate callus at the base of each collar, adaxial surfaces glabrous, scabrous, or sparsely pilose, apices often sharply pointed. Inflorescences terminal, exceeding the leaves, solitary spikelike racemes (a single spikelet in Z. minima), spikelets solitary, shortly pedicellate, laterally appressed to the rachises; disarticulation beneath the glumes or not occurring. Spikelets laterally compressed, with 1 floret; florets bisexual. Lower glumes usually absent; upper glumes enclosing the floret, chartaceous to coriaceous, awned, awns to 2.5 mm; lemmas thin, lanceolate or linear, acute to emarginate, 1-veined; paleas thin, rarely present. x = 10. Named for Carl von Zois (1756-1800), a German botanist.

Zoysia has 11 species. They are native to coastal sands between 42° N and 42° S and from Mauritius to Polynesia. Some species also grow in disturbed inland areas. Three species are used as lawn grasses in mesic tropical and subtropical areas, including parts of the Flora region. Because lawn grasses are rarely collected, the distribution maps for Zoysia show the states in which each species can be successfully grown rather than individual county records.

As is common with commercially important species, several cultivars of Zoysia have been developed, sometimes from hybrids. Whether or not they are hybrids, cultivars often exceed the normal range of variation for a species in one or more respects. This makes it difficult to account for them in a key. The following key is written for specimens that fall within the normal range of the species concerned. In employing it, caution must be used when interpreting blade widths because blades of Zoysia become involute or convolute under drought or salinity stress. In addition, hybridization has resulted in cultivars with vegetative characteristics more like those of one species and reproductive characteristics more like those of another species.

1.   Zoysia pacifica (Goudswaard) M. Hotta & Kuroki
Mascarenegrass, Korean Velvetgrass

Plants rhizomatous. Sheaths glabrous, overlapping; ligules 0.07-0.25 mm; blades to 3 cm long, to 0.5 mm in diameter, patent, involute to strongly convolute (the margins overlapping), mostly glabrous abaxially, abaxial calluses 0.2-0.6 mm, hairs about 1 mm. Peduncles included or extending to 1 cm beyond the sheaths of the flag leaves. Racemes 0.4-2 cm, with 3-12 spikelets. Spikelets 2.2-2.9 mm long, 0.5-0.8 mm wide, lanceolate to linear, unawned or awned, awns to 0.5 mm. 2n = 40.

Zoysia pacifica is less cold-tolerant than either Z. matrella or Z. japonica. It is not a common lawn grass in the Flora region, not even in the southern United States. The cultivar 'Cashmere' has many of the characteristics of Z. pacifica; it is probably derived from a hybrid between Z. matrella and Z. pacifica.

2.   Zoysia japonica Steud.
Japanses Lawngrass, Korean Lawngrass

Plants rhizomatous. Culm internodes 2-10 mm. Sheaths glabrous; ligules 0.05-0.25 mm; blades to 6.5 cm long, 0.5-5 mm wide, ascending, flat to loosely involute when fully hydrated, involute when stressed, surfaces glabrous or pilose. Peduncles exserted, extending 0.8-6.5 cm beyond the sheaths of the flag leaves. Racemes 2.5-4.5 cm, with 25-50 spikelets; pedicels 1.6-3.5 mm. Spikelets 2.5-3.4 mm long, 1-1.4 mm wide, ovate, awned, awns 0.1-1.1 mm. 2n = 40.

Zoysia japonica was the first species of Zoysia introduced into cultivation in the United States, with the introduction of the cultivar 'Meyer' in the 1950s. It is the most cold-tolerant and coarsely textured of the three species that have been introduced to the Flora region, and is the only species that is currently available as seed in the United States. The other two species treated here can be established from seed, but there are currently no commercial sources for either one in the United States.

3.   Zoysia matrella (L.) Merr.
Manilagrass

Plants rhizomatous. Culm internodes 5-40 mm, at least some on each plant longer than 14 mm. Sheaths glabrous; ligules 0.07-0.25 mm; blades to 7 cm long, 0.5-2.5 mm wide, patent, weakly involute when fully hydrated, to strongly involute when stressed, surfaces glabrous or sparsely pilose. Peduncles extending (0.3)1-6 cm beyond the sheaths of the flag leaves. Racemes 1-4 cm, with 10-40 spikelets; pedicels 0.6-1.6 mm. Spikelets 2.1-3.2 mm long, 0.6-1 mm wide, lanceolate, unawned or awned, awns to 1 mm. 2n = 20, 40.

Many of the Zoysia lawn grasses grown in the southern and eastern United States are derived from hybrids between Z. matrella and Z. pacifica or Z. japonica, and have retained many of the characteristics of Z. matrella. They are used as lawn grasses from Connecticut southwards, and have occasionally been found as escapes in that region.