Arvense is from the Latin arvum meaning 'cultivated field' and refers to the plants association with cultivation.
Corn Gromwell
Other Names:
Sheep weed
Stone weed
Wheat Thief
White Iron weed
Summary:
An erect, grey green, roughly hairy, winter growing, annual herb with small white flowers in spring.
Description:
Cotyledons:
Two. Oval. Stalked. Hairy on upper surface. Tip slightly indented. Sides convex. Base tapered.
First leaves:
Hairy on upper and lower surfaces. Club shaped. Tip slightly indented.
Leaves:
Alternate.
Stipules -
Petiole - Distinct petiole or leaf tapers toward the base.
Blade - Short, stiff, closely pressed hairs, rough to touch. Narrowly egg shaped to oblong, 15-100 mm long, 3-11 mm wide. Upper leaves tending to be more elliptical and half clasping the stem and half as long as the lower leaves, 15-40 mm long. Midrib sticks out underneath.
Stems:
Usually many stems arising from the base. Grooved. Maybe branched from base. 100-500 mm tall. Sparse stiff hairs that lie against the stem.
Flower head:
Long, loose, leafy terminal cyme.
Flowers:
White. On very short stalks, at the ends of stems and in the upper leaf axils. Each has a leafy bract at the base that is longer than the sepals. Flower parts arranged radially.
Ovary - 4 celled.
Style - 1.5 mm long. Arises from near the base of the ovary.
Stigma - 2 lobed.
Sepals - 5. Narrow, leaf like, free almost to the base, coarsely hairy (less so when in fruit), obvious midrib. 3-5 mm long. Persistent. Rigid, spreading and up to 10 mm long when in fruit.
Petals - 5. 3-8 mm tube with 1-2 mm long, rounded, spreading lobes. Hairy outside. Tubular with 5 longitudinal bands of hairs inside running from the base of the lobes to the stamens and a ring of 10, rounded, tiny scales, inside at the base surrounding the ovary.
Stamens - Attached below the middle of the corolla tube.
Anthers -
Fruit:
4 grey to brown or pale, hard, warty and wrinkled apart from the smooth areole with 2 tiny white warts, 2.5-4 mm long nutlets that detach from the receptacle and are enclosed by the calyx(sepal) lobes. Acute tip.
Weed of crops, wheat, cultivation, fallows, ephemeral creeks and disturbed areas.
Toxicity:
Contains toxic alkaloids but rarely causes problem.
Symptoms:
Liver lesions.
Treatment:
Avoid grazing dense infestations for long periods.
Avoid feeding cereal grain contaminated with Corn Gromwell seed to pigs, cattle or horses.
Legislation:
None.
Management and Control:
Thresholds:
Competes strongly with winter cereals causing yield reductions.
Eradication strategies:
Herbicide resistance:
Biological Control:
Related plants:
Plants of similar appearance:
Amsinckia, Paterson's curse, Heliotrope.
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P128. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P717. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P307-309. Diagram.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P564. Photo.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P116.
Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P22. Photos.
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). #206.1.
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). P547.