Capeweed

Arctotheca calendula (L.) Levyns

Synonyms - Arctotis calendula, A. calendulacca, Cryptostemma calendula, C. calendulacea, C. calendulaceum.

Family: Asteraceae.

Names:

Capeweed - refers to its origin, the Cape of Good Hope in South Africa and its weedy nature.

Other Names:

Cape Dandelion
Dandelion

Summary:

Capeweed is an autumn/winter germinating, stemless, rosette forming annual herb with broad, deeply lobed, succulent, leaves 30-250 mm long that have white furry hairs underneath and form a dense rosette. Yellow petalled daisy flowers about 40 mm diameter with a black to brown centre appear in spring on individual 200 mm stalks. The tiny woolly fruits are topped by minute scales.
It is a common weed of pastures, crops and roadsides, but also quite common in disturbed bushland and native to South Africa

Description:

Cotyledons:

Two. Oval to club shaped. Hairless. 10-20 mm long. Round tip. Indistinct merging petiole 1-2 mm long. Seedlings have a short hypocotyl and no epicotyl.

First leaves:

Paired, 10-20 mm long with a short petiole. Spear shaped with a round tip. May have scalloped edges. Green on top with a few hairs and white underneath with a dense mat of furry hairs.

Leaves:

Later leaves emerge singly. Succulent. Forms a rosette to 500 mm wide. Usually lie flat on the ground unless in dense crop or swards.
Stipules - None.
Petiole - Shorter than the blade and hairy.
Blade - Green on top white underneath. 30-300 mm long x 10-80 mm wide. Acute tip. Multiple and deeply lobed. Short, soft, white mat of downy, sometimes slightly sticky hairs underneath. Short, often mealy, hairs on upper surface that become rough to touch due to stiff hair bases as the leaf ages. Midrib prominent on underside.
Stem leaves - Lower ones are similar to rosette leaves, but have many multicellular and cobwebby hairs on the upper surface and are up to 250 mm long. Upper ones have no petiole and have fewer or no lobes.

Stems:

Often has no main stem. When present, it is prostrate, often striped, ribbed, succulent and woolly, up to 400 mm long and often has a small hollow core.
Flower stem - This is often called the stem and is white to green, unbranched, striped, hairy, fleshy, round or fluted and 50-300 mm long x 2-4 mm diameter.

Flower head:

Single flower head (involucre) on stalks that are slender, 2-4 mm wide x 50-300 mm long, erect, unbranched, glandular-hairy, white to green, striped, round or fluted and fleshy. Stalks are usually shorter than the subtending leaf.
Involucre is hemispherical, 10-15 mm diameter with many overlapping bracts in 4-5 unequal rows. The outer ones are egg shaped with spreading awl shaped tips and woolly with hairy edges. The inner bracts are oblong with thin black or purple edges.

Flowers:

Daisy like with 15-20 yellow 'petals' surrounding a black to purplish or brownish centre. 30-70 mm wide overall.
Florets - Outer florets are ligulate, 15-20 in a single row, sterile, 12-30 mm long, spreading, yellow with darker veins and often have a brown blotch at the base and a blackish tinge on the back. The ligules are spear shaped.
Disk florets, many, blackish purple, tubular, bisexual.
Ovary -
Stamens -
Anthers -

Fruit:

Achene. Oblong. 2 mm long. Covered with fine hair initially that form pinkish tangle of wool that hide the 6-8 short, spear to egg shaped, membranous, translucent, pappus scales.

Seeds:

Covered with pale brown wool. Up to 4,300 seeds per plant.

Roots:

Taproot, with many laterals.

Key Characters:

3-7 cm diameter daisy like flowers with yellow “petals” and a blackish or dark centre.
Lobed leaves that are green on top and whitish hairy underneath.

Biology:

Life cycle:

Annual. Germinates autumn/winter. Nearly all the seed germinates within a few weeks of the autumn rains and late germinations in crops are not common. Grows rapidly in warm temperatures often smothering companion plants in early winter. Flowers late-winter/spring. Dies off with onset of summer.

Physiology:

Generally considered drought tolerant and has the ability to survive false breaks but 7 reported lower rates of seedling survival than clover or ryegrass after a false break at Merredin in 1993.
Fairly tolerant to grazing.
Capeweed is more soil acidifying than clover on a per kg basis 8.
Capeweed tends to have higher cadmium levels than clover and grasses 9, 10, 11 and Zinc 10. Capeweed supplies about 3 times more cadmium to grazing animals than clover or annual ryegrass in typical field conditions 12.
Capeweed has higher levels of copper and molybdenum and lower levels of sulphur than clover during the growing season 13.
Remote sensing using the Plant Pigment Ratio (PPR) can be used to detect capeweed infestations in corps and pastures 14.
Capeweed has greater nitrogen uptake than either wheat or lupins which reduces nitrate leaching 15 in cropping systems and is very efficient at absorbing, storing and reducing soil nitrate levels in pasture systems 16.
Individual capeweed plants differ considerably in their response to potassium. In solution culture at 2.6 mu M dry weights of tops varied from 8-218 mg 17.

Reproduction:

By seed.

Flowering times:

July to November.

Seed Biology and Germination:

The survival of seed in the soil is likely to be very strongly influenced by the ecotype or location and the degree of burial that occurs. In WA it ranges from almost no carryover of seed from one season to the next to in excess of 20% of seed set being carried over for at least 2 years.
Wool around seed assists early germination.
Seeds are usually dormant at maturity with an after ripening period of 2-3 months. This is rapidly relieved by summer temperatures around 400C. Time and light breaks dormancy 18. Secondary dormancy may be initiated by low winter temperatures 19.
Long term dormancy is dependent on the ecotype with seed on the soil surface from the southern agricultural area of WA having >95% germination at the break of the season and seed from the northern agricultural area having less than 5% germination in the first year, 75% in the second season and 20% remaining dormant for more than 2 years with dormancy cycling to favour autumn germination (20). 21 argue that a large proportion of the seed might enter a persistent seed bank through a combination of embryo and seed coat based dormancy in the ecotypes they were using. Scarification of seed also reduces dormancy (18).
Seeds kept in the dark or buried will remain dormant longer than those exposed to light. Again this appears to be ecotype dependent as seeds in Portugal had almost complete germination at 15 deg C in continuous darkness 22, whereas in Australia, seed burial prevented germination 20.
Diurnal temperatures of 10/150C were optimal for germination in 23 work but higher at 250C in 24 WA data. Germination is very low at temperatures above 30 deg C 20. This results in strong autumn flushes of germination in Mediterranean environments.

Vegetative Propagules:

None but it transplants fairly readily.

Hybrids:

None.

Allelopathy:

None reported.

Population Dynamics and Dispersal:

Capeweed is favoured by 'false breaks'. Low rainfall events can result in capeweed germination before other species because the woolly seed covering attracts moisture and reduces desiccation. Capeweed can survive periods of drought better than most common agricultural species, so a dry period following good germinating rains increases the proportion of capeweed. Surveys show capeweed proliferated in years where germinating rains were followed by a 4-5 week dry period 25.
The RGR of capeweed is initially higher than clover and annual ryegrass under high fertility but competition for light was unlikely under grazed conditions unless the capeweed established some weeks earlier than other species 26. Early season RGR of capeweed is twice that of clover 24.
Seed is readily spread by animals, wind and water and in hay. It rapidly invades overgrazed or poorer pastures.
Viable Capeweed seed will pass through the gut of rabbits.
High continuous stocking rates with high levels of phosphate application lead to capeweed dominance in annual pastures and increased soil acidification 27. This may explain the predominance around stock camps.
During the growing season sheep select annual ryegrass then clover then capeweed then long storksbill (Erodium) giving the weeds a competitive advantage under grazing 28.
At high temperatures (28/32 deg C) and high light levels capeweed grows faster than subterranean clover and annual ryegrass, at lower temperatures (27/22 deg C) and light levels it looses its competitive advantage 24.
Increased levels of defoliation reduces root weights 29.
At low densities capeweed is more productive than clover or annual ryegrass. At high densities annual ryegrass is the most productive 29.
In summer dry matter loss of tops for capeweed is about the same as for clover and 2-3 times faster than grasses 30.
Defoliation has little effect on seed production unless the defoliation removed buds or flowers 31.

Origin and History:

South Africa.
First collected in Australia in 1834 in Albany, WA and soon after in Fremantle and Adelaide. There was probably multiple introductions as a contaminant of feed and packing. It took decades to establish in the Sydney region and spread to the interior agricultural areas mainly by human transport. The range of capeweed appears to be still expanding 32.
The development of ecotypes suited to marginal environments may assist this expansion.
Capeweed was probably introduced to Tunisia from Australia 33.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
Tunisia.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate, Mediterranean.
In WA, the capeweed content of pastures is higher in the lower rainfall wheat belt areas at 50% DM content than in the high rainfall grazing areas where it is 37% on average 25.

Soil:

On most soil types.
Prefers sandy soils and loams.
Soil type and topographical features influence the abundance of capeweed 25.
Capeweed tends to predominate on high P soils and long storksbill on low P soils.

Plant Associations:

Clover, Annual Ryegrass, Winter annuals.

Significance:

Beneficial:

Fodder, it is one of the most common species in many rain fed pastures in temperate Australia. Animal intake of capeweed can be marginal, it is a good accumulator of minerals and has good and similar crude protein and carbohydrate to clovers and grasses from autumn to spring but breaks down quickly in summer 34.
Does not host Root Lesion Nematodes (Pratylenchus neglectus or thornei)
Used in Spain to treat stomach disease 35.

Detrimental:

Weed of crops causing yield reductions due to competition in lucerne (36) cereals (37) autumn sown pastures (38). Weed of pastures displacing sown species. Weed of field peas (39).
Weed of cultivation, vineyards, orchards, vegetables (40), roadsides and disturbed areas.
Displaces native everlastings in the low rainfall areas.
Causes scouring in stock.
76% of cereal crops had capeweed infestations in NSW 41.
Has the ability to survive false breaks making control before cropping difficult.
Often transplants during cultural operations.
Taints milk.
Host for light brown apple moth and the larvae of 10 other species of Lepidoptera 42.
Carries the thrip transmitted tomato spotted wilt tospovirus (TSWV) 43 44.
Carries aphid transmitted cucumber mosaic virus (CMV) 45.
Alternate host for green peach aphid, blue green aphid and cowpea aphid and Redlegged Erarth Mite.

Toxicity:

Cattle, sheep, pigs and horses are affected.
It can accumulate nitrate levels high enough (2-4.7% dry matter) to cause toxicity to stock especially after spraying with hormone herbicides like 2,4-D. Early season spraying in warmer temperatures and in dull weather is associated with increased risk of toxicity. Avoid grazing with horses, pigs and young or breeding stock. Animals that have suffered previous nutritional stress appear to be more susceptible to poisoning.
May cause both nitrate and nitrite poisoning. Stressed, starved and unaccustomed stock are most susceptible.
Ruminants feeding on capeweed may scour but the causes are not clear.
Woolly seeds in unopened buds may cause hair balls and deaths in sheep.
May cause nasal granuloma in cattle that inhale pollen laden air for extended periods.
Causes hay fever and contact dermatitis in some humans.

Symptoms:

Depression, loss of appetite, pale mucous membranes, salivation, gasping, muscle tremors, staggering, collapse, coma and death. The blood may be chocolate coloured and clot poorly. Cattle may suffer rapid death within an hour of exposure.
In pigs enteritis and scouring may occur probably due to eating pollen.
Scouring, particularly when exposed to flowering capeweed in the field. However, feeding trials show that capeweed didn't cause scouring, was as nutritious as clover and annual ryegrass when green but intakes were reduced resulting in poorer sheep performance 46.

Treatment:

Remove stock from infestations. Avoid exposing stock to lush Cape Weed growth.
For nitrate poisoning, treat with injection by vein of 6-10 mL of 1% methylene blue for sheep or 100--200 mL for cattle.

Legislation:

None.

Management and Control:

Rotational grazing tends to reduce the build up of Capeweed in pastures 47 and favours the grass component. Spray grazing, Spray topping and pasture topping are economic methods of keeping levels low. Spray topping with glyphosate360 at 400 mL/ha during flowering of capeweed gave a 90% reduction in plants the following year (heavy grazing prior to spray topping had little effect) 48 49. 25 also reports that capeweed flower production is not affected by stocking rate.
Capeweed tends to build up moderate stocking rates and tends to disappear at very low very high stocking rates 50.
Diuron + MCPA provides very cheap control in cereals (37).

Thresholds:

It is very competitive in young crops and pastures.
Thresholds for spraying in cereals and lupins depend on the size of the capeweed compared to the crop.
For Cape Weed that has emerged at the same time as the crop, densities of 15 plants/m2 are usually worth spraying in cereals. For weeds that have survived the planting operation and transplants, 3-4 plants/m2 are often worth spraying.
In WA trials, 7-90 plants/m2 reduced wheat yields by 28-44%.
In lupins, 10 capeweed plants/m2 that germinated 6 weeks before the crop caused 100% grain yield loss; 10 plants/m2 that germinated with the crop caused no yield loss and 30 plants/m2 that germinated with the crop caused 20% grain yield loss. 30 capeweed plants that germinated 6 weeks after the crop caused no yield loss 51.
Control in cereals after tillering usually does not give a yield increase 52.
Competition from capeweed in annual pastures only seems to occur when biomass exceeds 1 t/ha 53.

Eradication strategies:

In Clover pastures, spray-grazing with 500-1000 mL/ha of 2,4-D amine(500g/L) in winter or spray-topping with 500 mL/ha paraquat(250g/L) at budding in spring for a number of years will lead to very low levels.
In crops there are a number of post-emergence options. Lontrel® and terbutryn are preferred because they have some soil residual action. In grass areas, picloram containing products provide long term control.
In bushland, overall spraying with 120 g/ha Lontrel®750 plus 0.25% wetting agent or hand spraying with 2.5 g Lontrel®750 plus 25 mL of wetting agent in 10 L water will provide good control and is safe on many native species. Glyphosate(450g/L) at 500-1000 mL/ha or 10 mL in 10 L of water is also fairly selective in bushland and roadside situations if applied when the plants are young (less than 100 mm wide) or at the budding stage to reduce seed set. Manual removal before flowering is effective.
Mowing is only effective if repeated regularly and close to the ground to prevent flowering.
Cultivation can be variable as Capeweed transplants readily in wet conditions. Grazing is generally ineffective as a control technique but intense rotational grazing can used to reduce the proportion of Capeweed present.
Replant shrub and tall growing species to increase shade in disturbed areas.

Herbicide resistance:

Resistance to diquat and paraquat has been reported from Victoria 54. It took about 20 years of fairly continuous use to develop resistance 55.

Biological Control:

A number of species have potential as biological control agents 56 but the importance of capeweed as a pasture species means they are not likely to be introduced until alternative pasture species are developed.
Redlegged Earth Mite feed on capeweed but prefer clover 57, however the damage to capeweed is greater than that to clover so infestations tend to favour the grass and clover components of mixed pastures 58. In spring they tend to prefer capeweed flowers 59. The closely related mite Halotydeus anthropus also occurs on capeweed.
Green peach aphid, blue green aphid and cowpea aphid are the predominant aphids on capeweed and legumes and are most abundant in spring 60.
Pasture day moth has a preference for capeweed over other weed species 61.
Junonia insect which normally feeds on plantains also feeds on capeweed 62.
Rutherglen bugs colonise capeweed at flowering and leave 6-10 weeks later 63

Related plants:

Beach daisy (Arctotheca populifolia)
(Arctotheca prostrata) roots at the nodes and the seeds are not woolly.

Plants of similar appearance:

Cape Weed is often confused with the Hedge mustards when young but can be distinguished from this and most other species by the white downy hairs on the underside of the leaf.
Capeweed (Arctotheca calendula) has a light underside and darker upper surface on the leaf.
Dandelion (Taraxacum officinale)
Flatweed (Hypochoeris radicata)
Fleabane (Conyza spp.)
Indian Hedge Mustard (Sisymbrium orientale) has 4 petalled flowers.
Hawkbit(Leontodon taraxacoides)
Ox tongue (Helminthotheca echioides)
Prickly Lettuce (Lactuca serriola)
Prickly Sow Thistle (Sonchus asper)
Rapistrum (Rapistrum rugosum) has 4 petalled flowers.
Smooth Catsear (Hypochoeris glabra)
Skeleton Weed (Chondrilla juncea) has backward pointing leaf lobes.
Slender Thistle (Carduus spp.)
Sow Thistle (Sonchus oleracea)
White Arctotis (Arctotis stoechadifolia)
Wild Radish (Raphanus raphanistrum) has 4 petalled flowers.
Wild Turnip (Brassica tournefortii) has 4 petalled flowers.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P84. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P891. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P376. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P680-681. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P159-160.

Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P16-17. Photos.

Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). p27. Diagrams.

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). #120.1.

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). P657. Diagrams.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P35. Diagram.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P40-41. Photos. Diagrams.

Acknowledgments:

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