Wheat

Triticum aestivum L.

Synonyms - T. vulgare, T. sativum.

Family: Poaceae.

Names:

Wheat

Summary:

An erect, one to many stemmed grass with dense, 4 angled, cylindrical seed heads and smooth, oval, golden grain that is furrowed on one side.

Description:

Cotyledons:

One.

Leaves:

Alternate. Rolled in the bud.
Blade - Flat, 10-20 mm wide by up to 300 mm long, tend to droop. Parallel sided. Clockwise twist.
Ligule - Membranous, translucent.
Auricles - 2 claw-like encircling the stem.
Sheath - Rolled and overlapping. Prominent veins.
Collar - May have a few hairs.

Stems:

Erect, 300-1200 mm tall. Branch from base.

Flower head:

Erect, somewhat 4 angled, cylindrical, dense, spike-like panicle, with a zigzag central stem (rachis), 50-120 mm long.

Flowers:

Spikelets - Single, broad, flat on one side and convex on the other. Hairy or hairless. Awned or awnless. No stalk. Alternate and sit in a kink on either side of the main stem or rachis. 3-5 flowered.
Florets - 2-5, bisexual, top 1 or 2 usually empty.
Glumes - 2, rigid, keeled, oblong, convex, 7 ribbed. Both the same size. Obtuse tip with a sharp point or awn. Hard and shiny when mature. Persistent.
Palea - 2 keeled with fine hairs on keels.
Lemma - 3-5, broad, keeled, asymmetric, many ribs, rounded on the back, stick out from the glumes. Sometimes awned or with a pinched tip. Hard and shiny when mature.
Ovary - Hairy at the top.
Stamens -
Anthers - Yellow to white.

Seeds:

Golden yellow, grooved, oval to oblong, free, 6-7 mm long grain. White or vitreous in the centre when broken. Hairs at the top. Usually 2-3 grains per spikelet.

Roots:

Fibrous to 1000 mm deep.

Key Characters:

Spikes cylindrical, compressed, not digitate, not enclosed within the leaf sheath.
Rachis jointed.
Spikelets sessile, densely grouped, solitary at each node of the rachis, subtended by 2 glumes, arranged on either side of the rachis, 2-5 bisexual florets or upper 1-2 empty.
1 or more glumes and/or lemmas awned.
Glumes obtuse or toothed.
Lemma entire, 3 or more, obtuse or toothed, 5-many nerved, hardened.
Free grain.
Adapted from J.M. Black, N.T. Burbidge and T.D. Macfarlane.

Biology:

Life cycle:

Annual. Seed germinates at any time of the year. Seedlings form 3-6 leaves then tiller. Flowering occurs in autumn or spring.

Reproduction:

By seed.

Flowering times:

September to October and May in SA.
September to May in Perth.
Spring, summer and autumn in WA.

Seed Biology and Germination:

Short after ripening period. No dormancy.

Vegetative Propagules:

None.

Hybrids:

Commercial cultivars may be hybrids.

Allelopathy:

Little reported.

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Middle East. Mediterranean. Western Asia.

Distribution:

ACT, NSW, QLD, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Mediterranean or temperate regions with winter dominant rainfall.

Soil:

A wide range of agricultural soils.

Significance:

Beneficial:

Major crop.
Palatable feed used for grazing, hay, chaff and grain.

Detrimental:

Weed of fallows, roadsides, stockyards and following crops competing with them or contaminating the grain.
Carries wheat diseases through 'break crops' such as grain legumes or canola.

Toxicity:

May cause grain poisoning.

Legislation:

None.

Management and Control:

Control not required in pastures or other areas as it usually disappears after one or two seasons. In other crops a number of selective herbicides are available. Can be mechanically removed from the grain of many other crops by grading.

Thresholds:

Depends on crop. Usually 10-20/m2.

Eradication strategies:

None required as it usually disappears after one or two years.

Herbicide resistance:

Varieties tolerant to imidazolinone herbicides (Clearfield® varieties) are available. Varieties tolerant to other herbicides are being developed.

Related plants:

Club Wheat (Triticum compactum) is similar but has a shorter seed head and the head is usually broadest near the top.
Durum Wheat (Triticum durum) is similar but has sharply ridge glumes with a bristle on one of the lemmas, and has oblong shaped grain that is often flattened and very hard compared to the other species. They have higher protein contents and are often used for pasta.

Plants of similar appearance:

Barley (Hordeum vulgare) is hairless where the leaf sheath joins the blade and the spikelets occur in groups of 3.
Oats (Avena sativa) has no auricles on the leaf.
Triticale.
Jointed Goatgrass.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P142. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P56-57. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P72.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1238.1.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P996.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P45. Diagrams. Photos.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P98. Diagrams.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.