Flatweed

Hypochaeris radicata L.

Family: Asteraceae.

Names:

Flatweed because the leaves form a flat basal rosette.

Other names:

Catsear
Cat's-ear
Common Catsear
Dandelion
Rooted Cat's-ear

Summary:

Flatweed 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 usually somewhat bristly but can be hairless. The flower stems often have galls. It a perennial but often acts as an annual in drier climates. It is difficult to distinguish from Smooth Cat's-ear (Hypochaeris glabra) which is an annual. 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 and no hypocotyl. Hairless.

First leaves:

15-25 mm long. Short merging stalk. Few long, stout hairs on the top of the leaf. Leaves grow singly. Edges may be slightly indented. Later leaves are more lobed.

Leaves:

Rosette often around 300 mm diameter.
Stipules - None.
Petiole - None.
Blade - 30-200 mm long x 3-60 mm wide, variable in size and shape, irregularly lobed, club shaped in outline, clasping base, stiff leathery texture, rounded tip. Variable hairiness from scattered coarse hairs to warts with stout hairs to long white hairs on upper surface. Fewer and usually shorter hairs on the lower surface. Edges smooth or with tiny hairs and slightly wavy. Sticky white sap oozes from midrib when cut.
Stem leaves - None. Small bract well below the flowers.

Stems:

Single to several from the centre of the rosette, slender, erect, fluted or round in cross section, solid but may be hollow below flowers, often branched. Hairs on lower section. Hairless and striped on upper section. Often swollen where they branch due to a wasp that causes lumpy galls. 2-3 mm wide. 50-1000 mm long. Round or fluted. Sticky white sap.

Flower head:

Corymbose panicle. Flowers borne singly on ends of long stems (peduncles) that are sparsely scaly towards the top and with a small bract some distance below the flower. Flower head (involucre) 8-25 mm long, oblong to cylindrical.

Flowers:

Yellow, 30-70 mm wide. Open in the morning and close in the afternoon.
Bracts - Overlapping, differing lengths, elliptical, 30-35 at the base of the flower in 4-5 rows. Smooth or bristly on the midrib or near the top.
Florets - Numerous, all ligulate, longer than the involucre.
Ovary - Flat receptacle with bracts between florets.
'Petals' - Yellow on top, greenish yellow underneath.
Stamens -
Anthers - Yellow.

Fruit:

Achene, brown, striped with lengthwise toothed ribs, cylindrical, 2.5-17 mm long, rough near the top. Plumose (feathery) white pappus. Pappus mounted on a beak in all seeds usually. Pappus bristles in 2 rows, the outer row shorter and almost simple or rough, the inner row longer and feathery.

Seeds:

Cylindrical, tapered.

Roots:

Taproot.

Key Characters:

Flowers longer than the involucre. Achenes usually all beaked. 30-35 bracts on the flower head (involucre).
Shiny leaves in a flat rosette.
Flower stems often have galls and are often branched.
Yellow 'flowers'.
Sticky white sap.

Biology:

Life cycle:

Annual or perennial. Germinates autumn to winter and occasionally in spring. Flowers all year with a flush in spring.

Physiology:

Tolerates nearly all conditions except inundation.

Reproduction:

By seed and perennial taproot.

Flowering times:

Most of the year in western NSW.
Most of the year in SA.
All year with a flush in spring in WA.
April to November in Perth.

Seed Biology and Germination:

Vegetative Propagules:

Taproot will re shoot when severed

Hybrids:

A number of varieties exist. Variety heterocarpa has the outer achenes with a small beak or without a beak.
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, North Africa.

Distribution:

ACT, NSW, SA, TAS, VIC, WA.
Throughout Tasmania. The most widespread weed in south east Australia.
Canada, Hawaii, Japan, New Zealand, South Africa, South America and USA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Wide range from coastal to alpine.

Soil:

Sandy to sandy clay loams, red earths and red brown earths, shallow stony hillside soils. Less frequent on grey clays.
Often in moister areas.

Plant Associations:

In many communities.

Significance:

Beneficial:

Palatable fodder.
Honey plant.

Detrimental:

Weed of crops causing yield reductions due to competition.
Weed of pastures, bush, lawns, gardens 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 control annual but not perennial forms of the plant. 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:

Smooth Cat's-ear (H. glabra) is similar but the outermost seeds are without a beak, it is generally hairless or has sparse hair and has shorter leaves and involucre and is generally smaller with smaller 'flowers'. It has 14-20 involucre bracts rather than 30-35. It is often very difficult to distinguish due to hybridisation.
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.) has leaves on the stems and no 'petals'.
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) has flowers with 4 petals.
Ox tongue (Helminthotheca echioides) has rough to touch leaves.
Prickly Lettuce (Lactuca serriola) has prickles on the stems.
Prickly Sow Thistle (Sonchus asper) has leaves on the stems.
Rapistrum (Rapistrum rugosum) has flowers with 4 petals.
Skeleton Weed (Chondrilla juncea) has backward pointing leaf lobes.
Slender Thistle (Carduus spp.) has purple flowers.
Sow Thistle (Sonchus oleracea) has leaves on the stems.
Wild Radish (Raphanus raphanistrum) has flowers with 4 petals.
Wild Turnip (Brassica tournefortii) has yellow flowers with 4 petals.

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. Diagram.

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P178. Photo.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P400. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P716. Photo

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.

Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P36. Diagram.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne). P144.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #672.3.

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.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P56. Diagram.

Moore, J.H. and Wheeler, J.R. (2002). Southern Weeds and their Control. Photos.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P55. Diagrams. Photos.

Acknowledgments:

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