Flatweed but this is more correctly applied to H. radicata.
Glabrous Cat's-ear
Summary:
Smooth Cat's-ear is a herb to 400 mm wide with yellow daisy type flowers up to 30 mm diameter borne on simple or branched, leafless stalks at any time of the year with a flush in spring to early summer. The small florets all have radiating petal-like blades. The tiny fly-away fruits are topped by a stalked ring of barbed to feathery bristles. The leaves form a flat rosette and are variable being entire to shallowly lobed, and smooth and hairless to somewhat bristly. The flower stems often have galls. It is usually an annual and difficult to distinguish from Flatweed (Hypochaeris radicata) which is often perennial. Hybrids between the two species are common.
Description:
Cotyledons:
Two. Club shaped, 7-16 mm with a round tip and short, 3-5 mm long stalk. Very short epicotyl. Hairless.
First leaves:
15-25mm long. Short merging stalk. Few long, stout hairs on top of leaf. Leaves grow singly.
Leaves:
Form a basal rosette.
Stipules -
Petiole - None.
Blade - 10-200 mm long by 3-60 mm wide, irregularly lobed, toothed or not lobed, club shaped in outline, clasping base. Hairless or a few coarse, simple hairs on upper surface and midrib of lower surface. Occasionally densely hairy on the upper surface. There may be tiny hairs on the edges. Sticky white sap oozes from midrib when cut.
Stem leaves - None. Small bract well below the flowers.
Stems:
Single or a few from the centre of the rosette, slender, erect, round, usually branched, hollow below flowers, 50-400 mm long by 2-3 mm wide, often have lumpy galls. Hairs on lower section. Hairless and striped on upper section. Sticky white sap.
Flower head:
Single, oblong to cylindrical, flower head on a long, sparsely scaly, hairless stalk (peduncle) at the ends of long branched stems.
Flowers:
Yellow, daisy type, 8-20 mm long by 30-70 mm wide. Open in the morning and close in the afternoon.
Bracts - Elliptical, overlapping, differing sizes in 4-5 rows. Hairless or with small spines near the top.
Usually 14-20 at the base of the flower head.
Florets - Many, the outer florets about as long as the involucre.
Ovary - Flat receptacle with bracts.
'Petals' - Golden yellow on top, greenish yellow underneath.
Stamens -
Anthers - Yellow.
Fruit:
Brown, striped with lengthwise ribs, cylindrical achene 2.5-17 mm long. Central ones tapering gradually with a long smooth beak. Edge ones with a short or no beak. Feathery pappus with an outer row of rough, slightly feathery hairs and an inner row of long feathery hairs.
Seeds:
Roots:
Taproot.
Key Characters:
Yellow flowers. Outer florets about as long as the involucre. 14-20 involucre bracts. Relatively hairless. Tends to be annual. Edge achenes beakless and central achenes beaked.
Biology:
Life cycle:
Annual or perennial. Germinates autumn to winter. Flowers all year with a flush in spring.
Physiology:
Reproduction:
By seed.
Flowering times:
Spring in western NSW.
October to December in SA.
April to November in Perth.
All year with a flush in spring in WA.
Seed Biology and Germination:
Vegetative Propagules:
None.
Hybrids:
There are several varieties. Variety Loiseleuriana has beaks on all achenes. Variety arachnoidea has no beaks on any achenes. Variety minima is a small and slender with heads of a few flowers and only 7-8 involucre bracts.
Hybridisation between H. glabra and H. radicata makes identification very difficult.
Allelopathy:
Population Dynamics and Dispersal:
Seed spread by wind and carriage on animals.
Origin and History:
Europe.
Distribution:
ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
Africa, New Zealand, South America, USA
Habitats:
Climate:
Mediterranean. Temperate.
Soil:
Wide range. Often abundant on sandy soils.
Plant Associations:
Significance:
Beneficial:
Fodder.
Detrimental:
Weed of crops causing yield reductions due to competition.
Weed of pastures, bush, horticulture, gardens, lawns, cultivation and disturbed areas.
Toxicity:
Causes stringhalt in horses, especially draught horses.
Symptoms:
Involuntary lifting or jerking up of the legs. Knuckling over at the fetlocks.
Treatment:
Remove horses from infested areas. Recovery may take 2 years.
Give vitamin B (thiamine) injections at 5-8 mg/kg body weight daily.
Legislation:
None.
Management and Control:
Spray grazing with 2,4-D amine provides partial control.
Rotational grazing reduces infestations by encouraging grasses.
Plant perennial pastures if possible.
Use a cereal crop sprayed with glyphosate pre plant and Lontrel® post emergence to clean up infested pasture paddocks.
Thresholds:
Eradication strategies:
Use a weed fork to extract the taproot if hand pulling.
Use 2-3 L/ha glyphosate(450g/L) on road shoulders to reduce the spread of seed in traffic slipstreams.
In bushland, 200 g/ha of Lontrel®750 as an overall spray or 4 g Lontrel®750 in 10 L water as a spot spray is fairly selective. Rosettes may be wiped with a mixture of 1 part glyphosate in 2 parts water. Alternatively, half a teaspoon of urea in the centre of the rosette will provide control. For small infestations, 50 mL Tordon®75-D in 10 L water will control growing plants and leave a soil residue to control seedlings for about 12 months. Apply herbicides regularly to prevent seeding. Plant perennials and tall growing species to reduce re-invasion.
Cultivation provides good control but leaves the area susceptible to re-invasion.
Mowing and grazing are ineffective and often favour its abundance. It will flower within two weeks of mowing.
Herbicide resistance:
Biological Control:
Related plants:
Flatweed (H. radicata) is similar but the outermost seeds have a beak, it has hairs and the leaves, stems and involucre are usually longer and 'flowers' larger. It has 30-35 involucre bracts rather than 14-20. It is often very difficult to distinguish due to hybridisation. It is a perennial but may act as an annual in drier areas.
White Flatweed (H. microcephala var. albiflora) has white flowers.
Plants of similar appearance:
Capeweed (Arctotheca calendula) has leaves with green upper surfaces and almost white undersides.
Dandelion (Taraxacum officinale) doesn't have branching flowering stems. Has regularly lobes leaves that aren't as leathery and do have petioles.
Fleabane (Conyza spp.)
Hawkbit(Leontodon taraxacoides) is very similar but doesn't have branching flowering stems. Has regularly lobes leaves that aren't as leathery. The cotyledons are narrower.
Indian Hedge Mustard (Sisymbrium orientale)
Ox tongue (Helminthotheca echioides)
Prickly Lettuce (Lactuca serriola)
Prickly Sow Thistle (Sonchus asper)
Rapistrum (Rapistrum rugosum)
Skeleton Weed (Chondrilla juncea) has backward pointing leaf lobes.
Slender Thistle (Carduus spp.)
Sow Thistle (Sonchus oleracea)
Wild Radish (Raphanus raphanistrum)
Wild Turnip (Brassica tournefortii)
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P105. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P939.
Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P178.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P400.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P716.
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). P100. Photo.
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). #672.1.
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). P687. Diagram.