Plants perennial; cespitose or not, sometimes rhizomatous. Culms 10-250 cm, usually erect. Sheaths glabrous or ciliate; auricles 0.2-1.5 mm or absent; ligules membranous; blades convolute or flat. Inflorescences terminal, distichous spikes, usually not disarticulating at maturity; middle internodes 7-30 mm; disarticulation usually beneath the florets and tardy, occasionally in the rachises. Spikelets 1-3 times the length of the middle internodes, solitary, appressed to ascending, often trullate and arching outwards at maturity. Glumes oblong to lanceolate, stiff, indurate to coriaceous, glabrous or with hairs, keeled or rounded at the base, usually more strongly keeled distally than below, margins often with a hyaline margin, apices truncate to acute, sometimes mucronate, unawned, without lateral teeth; lemmas 5-veined, coriaceous, glabrous or with hairs, truncate, obtuse, or acute, sometimes mucronate or awned, awns to 3 cm; anthers 3, 2.5-12 mm. x = 7. Name from the Greek thino, a shore weed, and pyros, wheat.

Thinopyrum includes approximately 10 species, most of which are alkaline tolerant. It is native from the Mediterranean region to western Asia. Four species are established in the Flora region; only T. intermedium and T. ponticum are common. The genus is sometimes included in Elytrigia Desv. or Elymus.

Thinopyrum differs from other Triticeae in its thick, stiff glumes and lemmas. These are several cells thick, even between the veins (Jarvie 1992b).

1.   Thinopyrum intermedium (Host) Barkworth & D.R. Dewey

Plants rhizomatous, often glaucous. Culms 52-115 cm, glabrous or hairy, sometimes hairy only on the nodes, lowest internode plus sheath about 3 mm thick. Sheaths mostly glabrous, often ciliate on the margins; auricles 0.5-1.3 mm; ligules 0.1-0.8 mm; blades 2-8 mm wide, flat, abaxial surfaces glabrous, adaxial surfaces usually sparsely strigose, sometimes also with shorter pubescence, 7-30-ribbed, ribs not prominent, margins whitish, thicker than the veins. Spikes 8-21 cm, erect or lax; middle internodes 7-12 mm; rachises pubescent, not disarticulating at maturity. Spikelets 11-18 mm, with 3-10 florets. Glumes oblong, weakly keeled distally, glabrous and mostly smooth or strigose with 1-1.5 mm hairs, hairs usually evenly distributed, keels scabrous, at least distally, midvein usually more prominent and longer than the lateral veins, margins not hyaline or hyaline near the apices, apices obliquely truncate or obtuse to acute, sometimes mucronate; lower glumes 4.5-7.5 mm long, 1.5-2.5 mm wide, 5-6-veined; upper glumes 5.5-8 mm long, 2-3 mm wide, 5-7-veined; lowest lemmas 7.5-10 mm, glabrous or with 1-1.5 mm hairs, hairs usually evenly distributed, sometimes only on the outer portion of the lemmas, apices occasionally awned, awns to 5 mm; paleas 7-9.5 mm, keels usually ciliate for 1/2 of their length; anthers 5-7 mm. 2n = 42, 43.

Thinopyrum intermedium is native to Europe and western Asia. It has been widely introduced in western North America for erosion control, revegetation, forage, and hay. One of its advantages for erosion control and revegetation is that it establishes rapidly in many different habitats. In its native range, it grows in dry areas with sandy or stony soils. In Europe, it forms sterile hybrids with Elymus repens; no such hybrids are known from North America.

Several subspecies have been recognized within Thinopyrum intermedium, usually based on differences in vestiture of the glumes and lemmas, presence or absence of lemma awns, and color of the plants. Assadi (1994) commented that there was little correlation between the different character states. He grew seeds from several wild plants and, even when most of the offspring resembled the parent plant, there was often segregation of other variants. Crossing experiments showed that hybrids between the morphological variants were fertile and usually had regular meiosis. He noted, however, that the plants with glabrous spikelets tended to grow in mesophytic habitats, those with hairy glumes and lemmas on dry slopes, and those with ciliate glumes and lemmas at the edges of fields and in wet places. This difference in habitat preference was reiterated by Ogle (2001). Because of this ecological distinction, they are formally recognized here as subspecies. Plants with hairs only on the outer edges of their lemmas are included under T. intemedium subsp. intermedium. They may be derived from crosses between the hairy and glabrous plants, a possibility that has not been experimentally evaluated. There seems to be little correlation between spikelet vestiture and that of the leaves and stems.

Thinopyrum intermedium subsp. barbulatum (Schur) Barkworth & D.R. Dewey
Pubescent Wheatgrass

Glumes usually hirsute all over, sometimes merely scabrous on the veins; lemmas hirsute throughout, hairs 1-1.5 mm.

There is no known difference in geographic distribution between subsp. barbulatum and subsp. intermedium. Ogle (2001) states that T. intermedium subsp. barbulatum is adapted to areas with 11-12 inches of rainfall per year.

Thinopyrum intermedium (Host) Barkworth & D.R. Dewey subsp. intermedium
Intermediate Wheatgrass

Glumes usually glabrous, sometimes scabrous over 1 or more veins; lemmas usually glabrous, sometimes with hairs on the outer edges.

There is no known difference in geographic distribution between subsp. intermedium and subsp. barbulatum. Ogle (2001) states that T. intermedium subsp. intermedium is adapted to areas with 12-13 inches of rainfall per year.

2.   Thinopyrum junceum (L.) Á. Löve
Russian Wheatgrass

Plants not cespitose, rhizomatous. Culms 27-49 cm, glabrous, lowest internode plus sheath about 3 mm thick. Sheaths glabrous; auricles absent; ligules 0.5-1.5 mm; blades 2-4 mm wide, convolute, abaxial surfaces glabrous, adaxial surfaces scabrous to densely pubescent, 3-8-ribbed, ribs narrow, prominent, margins not conspicuously thickened. Spikes 4-55 cm, erect; middle internodes 12-28 mm; rachises glabrous, disarticulating at maturity. Spikelets 14-30 mm, appressed to the rachises, with 4-8 florets. Glumes lanceolate, glabrous, midveins slightly longer and more prominent than the lateral veins, apices obtuse to acute, often mucronate, margins not hyaline; lower glumes 10-18 mm, keeled, keels prominent; upper glumes 9-16 mm; lemmas 10-16 mm long, 2-4.5 mm wide, glabrous; paleas 9-14 mm, keels ciliate for almost their entire length; anthers 6-12 mm. 2n = 42, 56.

Thinopyrum junceum is native to the coast of Portugal, the Mediterranean, and the Black Sea. In the Flora region, it is restricted to the coast of southern California. In its native range, it grows on maritime rocky coasts, shifting beach sands, and, occasionally, by brackish water near river mouths.

3.   Thinopyrum pycnanthum (Godr.) Barkworth
Tick Quackgrass

Plants rhizomatous. Culms 10-120 cm, glabrous, lowest internode plus sheath 2-3 mm thick. Lower sheaths ciliate; auricles absent or to 0.5 mm; ligules 0.3-0.6 mm, truncate, ciliate; blades to 35 cm long, 2-6 mm wide, flat or convolute, glaucous, adaxial surfaces 3-20-ribbed, ribs prominent, crowded, flattened, scabrous. Spikes 4-10 cm; rachises glabrous, not disarticulating at maturity. Spikelets 10-20 mm, with 3-10 florets. Glumes 8-10 mm, glabrous, oblong-lanceolate, 4-7-veined, keeled, keels asymmetric, scabridulous, midveins slightly longer and more prominent than the lateral veins, apices acute; lemmas 7-11 mm, glabrous, subobtuse, unawned, mucronate, or awned, awns to 10 mm; paleas keeled, keels ciliate; anthers 5-7 mm. 2n = 42.

Thinopyrum pycnanthum is native to the coasts of western and southern Europe. It is reported from scattered locations in the western United States and from Nova Scotia to New Jersey in eastern North America. In its native range, it grows in maritime sands and gravels or river gravels.

4.   Thinopyrum ponticum (Podp.) Z.W. Liu & R.R.-C. Wang
Tall Wheatgrass, Rush Wheatgrass

Plants cespitose, not rhizomatous. Culms 50-200 cm, glabrous, lower internode plus sheath about 3.5 mm thick. Sheaths ciliate on the lower margins; auricles 0.2-1.5 mm; ligules 0.3-1.5 mm; blades 2-6.5 mm wide, generally convolute, adaxial surfaces 1-8-ribbed, ribs rounded, prominent, spinulose, margins usually thinner than the ribs, pale green. Spikes 10-42 cm, erect; lower internodes 16-42 mm; middle internodes 9-19 mm; rachises glabrous, not disarticulating at maturity. Spikelets 13-30 mm, with 6-12 florets. Glumes oblong, glabrous, midveins about equal in length and prominence to the lateral veins, apices truncate, margins about 0.5 mm wide, hyaline; lower glumes 6.5-10 mm, keeled, keels occasionally scabrous distally; upper glumes 7-10 mm; lemmas 9-12 mm, glabrous; paleas 7.5-11 mm, keeled, keels ciliate; anthers 4-6 mm. 2n = 69, 70.

Thinopyrum ponticum is native to southern Europe and western Asia. In the Flora region, it is planted along roadsides for soil stabilization and is spreading naturally, in cooler areas, because of its tolerance of the saline conditions caused by salting roads in winter.

In its native range, Thinopyrum ponticum grows in dry and/or saline soils. It is sometimes treated as a subspecies of T. elongatum (Host) D.R. Dewey, a diploid species that grows in maritime regions of western Europe.