Sorghum bicolor (L.) Moench s. lat.
Synonyms - Sorghum bicolor complex, Sorghum vulgare.
Sorghum is from the Latin surrigo meaning to grow up referring to the tallness of some species or from the Medieval Latin surgum or suricum referring to Syrian corn.
Forage Sorghum because it is the sorghum grown for forage.
Other names:Broomcorn Sorghum
Summary:An erect, strong, robust annual to short lived perennial grass to 2.5 m tall with an open, pyramidal, spreading seed head and large, broad, flat leaves.
Leaves:Blade - 150-400(600) mm long x 30-80(120) mm wide, parallel sided with a tapering pointed tip. Hairless apart from an area on top near the ligule.
Ligule - Membranous, fringed, 5 mm long.
Auricles - None.
Sheath - Striped with thin white edges. Hairless.
Stems: Thick or slender, tufted, erect, up to 4000 mm tall, rarely branching.
Flower head:Large, loose pyramidal or somewhat contracted panicle, 80-400 mm long x 250 mm wide, many branches in rings around the main axis. Main stem (rachis) and branches usually hairy on ridges and near nodes. Spikelet cluster (racemes) 30-40 mm long on stalks 0.5-1.5 mm long with short hairs. Remains in tact for some time after maturity. Spikelet with seed breaks off with part of the stalk of the panicle still attached.
Flowers: Spikelets - In pairs on branches. Top one is a group of 3. Persistent and variable When shed they break of with a section of the panicle branch. Two types;
1) Stalkless spikelets, bisexual, egg shaped to oval, 4-7 mm long x 3-4.5 mm wide.
2) Stalked spikelet empty or male, reddish or purple.
Florets - 2 in each spikelet. Lower one reduced to an empty lemma. Upper one bisexual in stalkless spikelet.
Glumes - On stalkless spikelets, oval to egg shaped, about the same size, leathery except for thinner tip. Lower glume often hairy, rough on the keels, tip with 5-16 obvious nerves and 3 tiny lobes, edges rolled in and hairy. Upper glume 3-9 ribs, edges hairy.
Glumes on stalked spikelet, persistent, narrowly oval, 3-5 mm long. Lower one has 9-12 ribs. Upper one has 7-9 ribs.
Lemma - On stalkless spikelet - translucent, finely hairy. Lower one 2 nerved, awnless. Upper one 1 nerved often awned. Awn 5-13 mm long.
Seeds:White to dark brown. Spherical to slightly tear shaped with a groove or indentation. Often with a dark spot.
Roots:Fibrous up to 2500 mm long. Short lived perennial varieties may have a short thick rhizome.
Key Characters:Annual grass with no rhizomes or short lived perennial with a short thick rhizome.
Racemes not in pairs, supported by a common spathe.
Inflorescence a panicle, not enclosed in the leaf sheath, comprising both bisexual and male or sterile spikelets.
Bisexual floret single.
Spikelets several, usually in pairs at least towards the base of the raceme.
Glumes of fertile spikelets not keeled, lacking pits, persistent spreading hairs especially on the upper third.
Lemmas 2 or more, awned, 1st lemma sterile or male.
Annual or short lived perennial. Summer growing. Flowers in May.
Flowering times:Summer to autumn in western NSW.
May in Perth
Summer to autumn in WA.
Seed Biology and Germination:Vegetative Propagules:
None or occasionally from short rhizome in some varieties.
Hybrids:Many varieties and crosses.
Columbus grass (Sorghum X almum) are the fertile hybrids between Johnson Grass (Sorghum halepense) and cultivated Sorghum (Sorghum bicolor) and some are these are useful fodders.
At least six cultivars recognised; Early Orange, Sacaline, Sugar Drip, Sumac, White African and Tracy.
Hybrid varieties include; Bantu, FS-22A, Lahoma, Piper, S66, Sudax SX-11A, and Zulu.
Allelopathy:Population Dynamics and Dispersal:
Spread by seed and mainly by intentional planting.
Origin and History:Sudan. Tropical Africa. Central Asia.
Distribution:NSW, NT, QLD, VIC, WA.
Courtesy Australia's Virtual Herbarium.
Requires reliable summer rain or irrigation.
Tropical cereal crop and fodder. Cultivated since pre-historic times.
Grown for edible syrup.
Grown for hay and silage.
Seed heads used for brooms.
Detrimental:Weed of rotation crops and disturbed areas.
Toxicity:May be toxic when stressed, frosted, wilted or stunted. Produces HCN and causes cyanide toxicity. Young shoots are probably the most toxic.
Sweet forage types are more likely to be toxic than the grain types.
May contain sufficient nitrate to cause nitrate toxicity.
Milo, Sudan Grass, Sudax, Sugar Drip and Zulu have all been associated with occasional stock problems in Australia.
Management and Control:Thresholds:
It usually disappear naturally. If persistent, it is probably a weedy biotype or is in a disturbed situation. Prevention of seed set for a year or two should provide control.
Herbicide resistance:Tolerant to triazine herbicides.
Biological Control:Related plants:
Annual Native Sorghum (Sorghum stipoideum)
Broom Millet (Sorghum dochna)
Brown Sorghum (Sorghum nitidum)
Columbus grass (Sorghum X almum) are the fertile hybrids between Johnson Grass (Sorghum halepense) and cultivated Sorghum (Sorghum bicolor) and some are these are useful fodders such as Columbus grass.
Downs Sorghum (Sorghum timorense, Sorghum australiense)
Forage Sorghum (Sorghum bicolor)
Johnson Grass (Sorghum halepense) is very similar but has larger aggressive rhizomes and the spikelets detach from the seed head branches.
Plume Sorghum (Sorghum plumosum)
Sudan grass (Sorghum sudanense) has a softer seed head and the seed doesn't protrude from the outer glumes.
Wild Sorghum (Sorghum arundinaceum, Sorghum leiocladum, Sorghum arundinaceum, Sorghum verticilliflorum)
Plants of similar appearance:Grasses.
References:Ciba Geigy (1980) Grass Weeds 1. CIBA GEIGY Ltd, Basle, Switzerland. P135. Diagrams.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P139.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P351-352.
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). P70.
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). #1147.4.
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). P989.
McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P21. Diagram.
Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P86. Diagram.
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.