Pigweed

Portulaca oleracea L.

Synonyms - Portulaca spp. affinity Portulaca oleracea.

Family: - Portulacaceae.

Names:

Portulaca is the Latin name for purslane.
Pigweed.

Other names:

Common Pigweed
Common Purslane
Inland Pigweed.
Munyeroo
Neverdie
Purslane
Red Pigweed

Summary:

A prostrate, succulent, running annual herb that often forms dense mats with spoon shaped, shiny leaves, red stems and 4-6 petalled, yellow flowers from August to March.

Description:

Cotyledons:

Two. Fleshy, oval. Tip rounded, Sides convex. Base rounded. Petiole shorter than the blade.

First leaves:

Fleshy, paired, triangular. Tip flat to roundish. Edges convex. Base tapered. Short petiole. Red stem.

Leaves:

Fleshy, mainly alternate, spiral to almost opposite arrangement. Turn black on drying.
Stipules - Occasionally a remnant consisting of a few, 1 mm long hairs
Petiole - Almost none.
Blade - Egg shaped to wedge shaped, thick, shiny, 10-30 mm long by 6-15 mm wide. Flat or blunt tip sometimes with a notch. Sides straight angular to convex. Base tapered Surface hairless and sometimes tinged with red or purple.

Stems:

Fleshy, low lying to bending upwards, 100-400 mm long, branched, often reddish, many arising from the base. Hairless. May form a mat up to 150 mm thick.

Flower head:

1-30 flowers in leaf axils.

Flowers:

No stalk. Yellow up to 5 mm diameter.
Ovary - Half inferior. Style 1.5-2 mm long with 4-6 stigmas(branches) 1.5-2 mm long.
Sepals - 3-6 mm long, keeled, fleshy, thin membranous edges. Joined at the base and to the lower part of the ovary. Tube breaks off just below the top of the ovary.
Petals - 4-6, egg shaped to wedge shape. 4-7 mm long by 2-5 mm wide, yellow, joined at the base. Only just longer than the sepals.
Stamens - 8-15.
Anthers -

Fruit:

Egg shaped, flat topped, membranous capsule, 3-5 mm long with many seeds. Hat (operculum) about the same length as the base and breaks off when mature taking the sepals and petals with it.

Seeds:

Dull to shiny black, many, globular to egg shaped, 0.6-1 mm diameter. Tip round. Edges convex. Base pointed to flat with stalk remnant. Surface finely dimpled and grooved.

Roots:

Taproot with many laterals.

Key Characters:

Prostrate succulent stems.
Leaves flat, succulent, oblong-cuneate.
Stipular hairs minute or absent.
Flowers sessile in the leaf axils.
Petals, yellow and scarcely exceeding the sepals.
Ovary inferior or half inferior.
From J.M. Black, N.T. Burbidge.

Biology:

Life cycle:

Annual. Seeds germinate from spring to summer and the plant grows over the warmer months and may form dense mats. Flowers August - March.

Physiology:

May accumulate oxalates and nitrates.

Reproduction:

By seed.

Flowering times:

Summer in western NSW.
Summer in SA.
August to March in Perth.
Summer in WA.

Seed Biology and Germination:

Vegetative Propagules:

None.

Hybrids:

A variable species and some taxonomists split it into several groups.
The inland forms are usually referred to as Munyeroo and Inland Pigweed and the coastal forms as Pigweed or Purslane

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Cosmopolitan. Temperate and tropical areas.
Probably introduced as a contaminant of other seeds.
In WA it is probably introduced to the south west and native to the rest of the state.

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate. Warm temperate. Mediterranean. Tropical. Sub tropical.
More abundant in high rainfall areas.

Soil:

On a wide range of soil types.

Plant Associations:

Many.
Often occurs with Native Spinach (Tetragonia tetragonoides)

Significance:

Beneficial:

Palatable, nutritious fodder under most conditions.
Used as a vegetable by pioneers and aboriginals.
Seed used for bread or cakes.

Detrimental:

Competitive weed of vegetables, horticulture, gardens, pasture, crops and disturbed areas.
Carries Xylella fastidiosa disease of grapes.

Toxicity:

Nitrate and oxalate toxic to sheep and cattle. Total oxalate levels range up to 13.3% and nitrates up to 18.8% KNO3 equivalent.
Most field cases of poisoning occur when hungry stock are released onto succulent stands growing in fertile conditions. Under normal conditions it usually causes no more than mild scouring.

Symptoms:

Oxalate poisoning.
Nitrate poisoning.

Treatment:

Oxalate poisoning.
Nitrate poisoning.
Don't expose hungry stock to heavy infestations. Don't stress or drive stock that have been grazing infested areas.

Legislation:

None.

Management and Control:

Grazing normally controls it.

Thresholds:

Eradication strategies:

Prevent seed set.
Increase grazing intensity.

Herbicide resistance:

Biological Control:

Related plants:

Slender Pigweed (Portulaca filifolia) has cylindrical leaves.
Large Pigweed (Portulaca intraterranea) has longer petals that are twice as long as the sepals.
Portulaca grandiflora is the large, red to white flowered ornamental Portulaca with cylindrical leaves.
Portulaca pilosa has pink flowers and obvious hairs more than 5 mm long in the leaf axils and parallel sided leaves and is found in the Kimberly and Pilbara.

Plants of similar appearance:

Australian Crassula, Dense Crassula, Spreading Crassula (Crassula spp.)
Chickweed (Stellaria media)
Four-leaved Allseed (Polycarpon tetraphyllum)
Mouse-eared Chickweeds (Cerastium spp.)
Pearlwort (Sagina apetala)
Petty Spurge (Euphorbia peplus) exudes a white sap when damaged.
Pimpernel (Anagallis arvensis)
Waterblinks (Montia spp.)
Pigweed (Portulaca spp.)

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P210. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P345-346. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P159-161. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P300. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P585.

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). P202-203. 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). #1014.3.

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). P101.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P42. Diagrams.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P114. Diagrams. Photos.

Acknowledgments:

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