Cotula australis (Sieber ex Spreng.) Hook. f.
Synonyms - Anacyclus australis
Cotula is from the Greek kotile meaning small cup referring to the shape of the flower or the concave base of the stem clasping leaves.
Australis is Latin for southern and refers to its Australian origin.
Other names:Batchelor's Button because of the yellow button like flowers.
Carrot weed because it has carrot like leaves.
Summary:A low growing annual or perennial herb with much divided (carrot like), hairy leaves and yellow (or white) button like flower heads with no 'petals' on slender stalks from spring to autumn.
Two. Oval, 2-3 mm long, round tips. Base tapered. Hairless. No petiole. Short hypocotyl and no epicotyl.
First leaves:Paired, oval to spear shaped, 15-20 mm long, pointed tip, smooth edge without lobes. Merging leaf stalk. Few long thin hairs on both surfaces. Later leaves grow singly.
Leaves:Rosette 100-300 mm wide. Alternate, may appear paired, membranous. As the plant grows the leaves become more lobed.
Stipules - Lobed and stem clasping.
Petiole - Short, on rosette and lower leaves. Base of petiole is stem clasping.
Blade - Once or twice deeply lobed, the segments with 3 or more narrow, acute tipped lobes, 10-20 mm long overall. Few hairs on upper side, long fine hairs on the lower surface. Carrot like. No minute dots or pits on the upper surface.
Stem leaves - Alternate. Up to 30 mm long. Sparse hairs on top with more hairs underneath. Lower leaves stalked, upper leaves clasp stem with lobed papery bases.
Stems:Up to 200 mm long. Round, solid, prostrate, semi erect or with short erect stems. Branched from the base and along their length. Forms roots near the base. Few fine hairs.
Flower stem - long and slender.
Flower head:At the ends of stems. Yellow to greenish white, single, hemispherical flower head, 3-5 mm wide, on a long, slender, erect, leafless flower stalk extending well above the foliage.
Flowers:Florets - 3-4 outer rows of fertile florets, without corollas surrounding inner rows of about 20 barren, hermaphrodite florets with 4 toothed, tubular, yellow corollas.
Bracts - Many, oblong to lance shaped, obtuse tip, sparsely hairy or hairless.
Ovary - Flat receptacle.
Petals - None.
Fruit:Achene, light brown, egg shaped, tiny, flattened, smooth, with a narrow, thick wing and slightly stalked. Tiny hairs between the thickened edges on both faces. Achenes of barren florets, narrower, not as flattened, have no wing and virtually no stalk and tiny hairs on both faces.
Short taproot with many fibrous roots.
Key Characters:Leaves pinnatisect, the ultimate lobes linear-lanceolate. Female flowers numerous in several rows. Female flowers without corollas. Receptacle flattish.
Annual or perennial. Seed germinates from autumn to spring and the plants grow rapidly, producing flower stems in late winter to spring and flowering soon after. Plants usually die (annual) or the top growth dies (perennial) as summer approaches.
By seed and re growth from the crown.
Flowering times:Mainly spring in NSW.
August to November in Perth.
August to May in WA.
Seed Biology and Germination:Vegetative Propagules:
Population Dynamics and Dispersal:
Spread mainly by seed.
Origin and History:Australia and New Zealand.
Distribution:ACT, NSW, QLD, SA, TAS, VIC, WA.
Distributed throughout Tasmania.
Courtesy Australia's Virtual Herbarium.
Soil:Wide range of soils.
Most abundant in winter waterlogged areas.
Weed of crops, pastures, gardens, lawns, playing fields, stream banks and disturbed areas.
Rarely eaten by stock probably because of its odour.
Often becomes a significant weed when pastures are bared during renovation.
Toxicity:Not recorded as toxic.
Legislation:Noxious weed of WA (Pest plant in Melville).
Management and Control:Thresholds:
Manually remove isolated plants.
Spray with hormone herbicides in winter before flowering.
A number of other herbicides provide good control in various situations.
Herbicide resistance:Biological Control:
Creeping Cotula (Cotula reptans)
Ferny Cotula (Cotula bipinnata)
Funnel weed (Cotula turbinata) has flowers with a yellow centre and small white petals and has a hollow stalk below the flower head.
Waterbuttons (Cotula coronopifolia) has much fleshier leaves and is hairless.
Plants of similar appearance:Cotula is very similar in appearance to Lesser Swinecress, particularly in the seedling stage if the cotyledons are absent. The early leaves of Cotula are more regularly lobed and hairy. Swinecress is hairless. The leaflets of Cotula also lack the distinct "cressy" smell of Swinecress. The leaflets of Cotula are usually pinnately lobed while those of Swinecress usually have lobes on side only. The terminal lobe of Cotula is often trifid, and that of Swinecress single.
In lawns it is often confused with Jo-Jo (Soliva pterosperma) because it has similar carrot like leaves but Jo-Jo has inconspicuous green flowers, and prickly seeds nestled in the leaf bases.
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P97-98. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P881.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P369.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P670. Photo.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P40. Diagram.
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). #361.1.
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). P674.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P280-281. Photos.
Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P52. Diagrams. Photos.
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