Streaked Arrowgrass.

Perennial wetland herb, 3–50 cm high. Rhizome glabrous, c. 1–2 mm diam. Tubers absent. Leaves in spaced tufts, terete, or plano-convex to flat, 2–45 (–65) cm long, 1–5.5 mm diam.; ligule prominent, obtuse, 0.5–5 (–7) mm long. Scape at fruiting terete, (1–) 3–32 (–45.5) cm long, 0.2–2.5 mm diam. Infructescence a spike-like raceme, (0.3–) 2–22 (–28.5) cm long, 4–11 mm diam.; pedicels (0.4–) 1–3 (–5) mm long. Fruits c. 2–250 per infructescence, ± globular to very broadly ovoid, 1.5–3 mm long, 1.5–3 mm diam. Carpels 6, fully united ventrally, 3 fertile alternating with 3 sterile; mature fertile carpels shortly tapered at apex, the dorsal surface with 3 obtuse longitudinal ridges; sterile carpels dorsally obtuse, narrower than fertile ones, forming a semi-persistent 3-winged central axis.

Flowers and fruits all months, chiefly November–April in Tasmania.

Native.

Distributed chiefly in coastal and near-coastal sites in all States across southern mainland Australia from about Dandaragan, Western Australia, to near Byfield, Queensland, excepting the Nullarbor Plain between Israelite Bay and Fowlers Bay; also on Lord Howe Island and in Tasmania, including the islands of Bass Strait. The furthest inland occurrences are in Tasmania (widespread), South Australia (northern Mount Lofty Ra., Murray River at Berri and Loxton, and an outlying record from Lake Callabonna) and Victoria (near Dimboola and Euroa). Also native to New Zealand, N and S America, and S Africa; introduced to Europe (Iberian Peninsula).

Occurs in moist, usually sandy or peaty soils or in shallow water to 20 cm deep, in ephemeral to permanent, still to flowing, saline or fresh waters. Sites include salt marshes and tidal estuaries, beach seepages above high tide mark, coastal interdune swamps, stream and lake edges, clay flats, and an inland mound spring. On Lord Howe Island forms a dense zone in sandy mud beside the creek in Old Settlement Bay (Green 1994).

W.A.: S coast, E of Augusta, R.D. Royce 3233a (PERTH).

S.A.: Newikie Creek, 35 km NE of Burra, B. Copley 5040 (AD).

Qld: Bribie Island, 5.5 km S of the N tip, G.N. Batianoff 1400 (BRI).

N.S.W.: Marley Lagoon, Royal National Park, E.F. Constable 6704 (NSW).

L.H.Is.: Old Settlement Beach, J.D. McComish 190 (K); loc. id., L.A.S. Johnson & A.N. Rodd 1229 (K, NSW); Johnsons Beach, M.D. Crisp 4583 & I.R.H. Telford (CBG), fide Green (1994: 406).

Vic.: Fitzroy River at Heywood township, H.I. Aston 2759 (AD, CANB, MEL, NSW).

Tas.: Ocean Beach, W coast, A. Moscal 5467 (HO).

Plant size varies greatly with water depth, stranded populations producing small depauperate tufts with few-flowered inflorescences. Some other differences appear genetic and the complex included here under Triglochin striata is in need of revision. Certainly the terete-leaved plants of saline wetlands appear consistently distinct from the flat-leaved individuals found generally in fresh water.

For treatment of Triglochin striata occurring on Lord Howe Island see Green (1994: 62).

(Often as Triglochin striatum): H.I. Aston, Aquatic Plants of Australia 247, fig. 99 (1973, 1977); G.R. Sainty & S.W.L. Jacobs, Waterplants of New South Wales 270–271 (1981); J.P. Jessop & H.R. Toelken (eds), Flora of South Australia 4th edn, 4: 1716, figs 766H (1986); N.G. Wheeler et al., Flora of the Perth Region 2: 712, fig. 265A (1987); Fairley & P. Moore, Native Plants of the Sydney District 322, pl. 1176 (1989); T.D. Stanley & E.M. Ross, Flora of South-eastern Queensland 3: 13, fig. 2C (1989); G.J. Harden (ed.), Flora of New South Wales 4: 20 (1993); W.M. Curtis & D.I. Morris, The Student's Flora of Tasmania 4B: 15, fig. 5A (1994); A.J.G. Wilson (ed.), Flora of Australia 49: 421, fig. 93E (1994); K.A.W. Williams, Native Plants of Queensland 4: 374–375 (1999); G.R. Sainty & S.W.L. Jacobs, Waterplants in Australia 3rd edn: 180–181 (1994); N.G. Walsh & T.J. Entwisle (eds), Flora of Victoria 2: 141, 29k–l (1994); J.R. Wheeler et al., Flora of the South West 1: 337, 339 (2002); G.R. Sainty & S.W.L. Jacobs, Waterplants in Australia 4th edn: 208–209 (2003); A. Wilson (ed.), Flora of Australia 39: 63, fig. 14C–G (2011).

Aston, H.I. (1973, 1977). Juncaginaceae, Aquatic Plants of Australia, pp. 241–248. (Melbourne University Press: Melbourne).

Aston, H.I. (2011). Juncaginaceae, in Wilson, A. (ed.), Flora of Australia 39: 53–84. (ABRS: Canberra/CSIRO Publishing: Collingwood).

Buchenau, F.G.P. (1903). Scheuchzeriaceae, in Engler, H.G.A., Das Pflanzenreich Heft 16, IV. 14: 1–20.

Conn, B.J. & Aston, H.I. (1994). Juncaginaceae, in Walsh, N.G. & Entwisle, T.J. (eds), Flora of Victoria 2: 137–146. (Inkata Press: Melbourne), as Triglochin striatum.

Fairley, A. & Moore, P. (1989). Native Plants of the Sydney District. (Kangaroo Press: Kenthurst).

Gardner, R.O. (1976). Binucleate pollen in Triglochin L. New Zealand Journal of Botany 14(1): 115–116.

Green, P.S. (1994). Juncaginaceae, in Wilson A.J.G. (ed.), Norfolk Island & Lord Howe Island. Flora of Australia Volume 49Oceanic Islands 1, pp. 405–406. (Australian Government Publishing Service: Canberra).

Jacobs, S.W.L. (1993). Juncaginaceae, in Harden, G.J. (ed.), Flora of New South Wales 4: 19–21. (New South Wales University Press: Kensington), as Triglochin striatum.

Morris, D.I. (1994). Juncaginaceae, in Curtis, W.M. & Morris, D.I., The Student's Flora of Tasmania 4B: 14–17. (St David's Park Publishing: Hobart), as Triglochin striatum.

Randell, B.R. (1986). Juncaginaceae, in Jessop, J.P. & Toelken, H.R. (eds), Flora of South Australia 4th edn, 4: 1715–1728. (South Australian Government Printing Division: Adelaide), as Triglochin striatum.

Rye, B.L. (1987). Juncaginaceae, in Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. & Macfarlane, T.D., Flora of the Perth Region 2: 720–723. (Western Australian Herbarium, Department of Agriculture: W.A.).

Sainty, G.R. & Jacobs, S.W.L. (1981). Waterplants of New South Wales. (Water Resources Commission: Sydney).

Sainty, G.R. & Jacobs, S.W.L. (2003). Waterplants in Australia: a field guide 4th edn. (Sainty and Associates: Sydney).

Stanley, T.D. (1989). Juncaginaceae, in Stanley, T.D. & Ross, E.M., Flora of South-eastern Queensland 3: 12–14. (Queensland Department of Primary Industries: Brisbane).

Thompson, J. (1961). Juncaginaceae. Contributions from the New South Wales National Herbarium, Flora Series 16: 77–80.

Wheeler, J.R., Marchant, N. & Lewington, M. (2002). Juncaginaceae, in Flora of the South West. Bunbury, Augusta, Denmark Volume 1. Flora of Australia Supplementary Series 12, pp. 337–339. (Australian Biological Resources Study, Canberra, Conservation and Land Management, Como and University of Western Australia Press: Crawley), as Triglochin striatum.

Revised edition published 17 September 2021. Adapted from Aston (2011). Updated by P.G. Kodela (September 2021).