Pigweed (Portulaca oleracea)
Pigweed is also known as Common Purslane, and is a prostrate, succulent annual weed that often forms a dense mat. It competes for available soil moisture and nutrients, screens out light to the soil surface, and prevents seedling emergence. Common Purslane has red stems that originate from a central point, and radiate out like spokes of a wheel.
Pigweed is not the same as Horse purslane (Trianthema portulacastrum).
Why is Pigweed such a problem?
- Pigweed is an alternative host of pests and diseases such as Root Knot, Pin, and Reniform nematodes.
- It is a highly invasive weed and one reason for this is Pigweed produces a large amount of seed. One plant produces up to 250,000 seeds over a season. Pigweed seed survives in the ground for several years, but germinates rapidly after soil disturbance and when it is exposed to light.
- Pigweed re-grows vegetatively.
- It is drought tolerant, although it does best in moist, fertile soils.
- Pigweed has negative allelopathic effects on seed germination, and seedlings.
After you read this, you will be able to:
- Identify Pigweed or Purslane.
- Know the habitat of Pigweed.
- Know the best cultural and chemical options to control Purslane.
Pigweed produces a large numbers of seeds, and quickly colonises warm and moist sites. It is also able to regrow from stem or root fragments.
A unique competitive advantage of Pigweed is its ability to switch from C4 metabolism to crassulacean acid metabolism (CAM). This occurs in the presence of short days or when it is under drought stress. This means Pigweed closes its stomata during the day in dry conditions to reduce water loss, and opens them at night to take in CO2 it needs for photosynthesis.
How to Identify Pigweed.
Pigweed has a branched, often red creeping, fleshy hairless stem, that is 20 to 50 cm long
Category: Purslane is a broadleaf (Dicot) weed.
Flower: Pigweed flowers are yellow, have 4 to 6 petals (often 5), and are 3 to 10 mm long. These are often single or in small clusters, and you can see them in the forks of leaves.
Height: Pigweed is a prostrate weed.
Leaf length: The hairless wedge-shaped leaves of Pigweed, have alternate along stems, and are 5 to 25 mm long,
Leaf width: The leaves of Pigweed are 3 to 15 mm wide.
Pigweed Reproduction.
Pigweed spreads mainly by seeds but vegetative reproduction is possible from stem fragments.
The seeds germinate in the late Spring and through the Summer. Pigweed seeds spread long distances by wind, water, and by passing through the guts of birds. The seeds remain viable for up to 40 years.
Pigweed seedlings emerge once temperatures exceed 24°C, and after rainfall. Four to six weeks later it emerges, the plants flower, and then have several flushes of flowers depending on the conditions.
Mature Pigweed produces seed within as little as 6 weeks of germination. Purslane plants are susceptible to lower temperatures, and begin to die once temperatures begin to fall in the early Autumn. After an irrigation or rainfall, Pigweed germinates very near to or at the soil surface in large numbers.
The burial depth of Pigweed seed is also a significant factor in the germination. Seedling emergence is greatest at the soil surface, and declines with increasing soil depth
The fleshy stems of Common Purslane can remain moist and viable for several days after cultivation.
Comments: Pigweed is thick, and flat at the nodes. Its taproot is white or brown in colour with fibrous hairs that reach to a depth of 30 to 50 cm. The stems of are maroon-purple, hairy, and erect.
Habitat: Pigweed is found from sea level up to about 2500 m. It is a common weed of crops, pastures, gardens, disturbed sites, waste areas, footpaths and roadsides. It favours high fertility soils with moderate moisture, but can grow in nearly all soil types.
For more information on weeds check out our weed ID Chart.
The distribution map of Pigweed in Australia is courtesy of The Living Atlas of Australia.
How to control Pigweed.
You can control Purslane or Pigweed by cultural and chemical means, but successful management of this weed is best if you adopt an integrated approach.
Cultural control of Pigweed:
In healthy, well-established turfgrass, Pigweed is usually not a problem. It is more of a problem in weak, poorly maintained turfgrass. Therefore, feed your turf properly and cut it at the right height to maintain healthy, competitive turfgrass.
The first step to manage Pigweed is to prevent it in the first place. Once Common Purslane establishes it is difficult to control. Avoid bringing Common Purslane into un-infested areas and clean equipment like mowers etc. before they enter clean areas.
Personally we have seen big issues with Pigweed after cultivation, as this tends to bring deeper weed seeds to the surface where they then germinate after irrigation.
If Purslane is flowering remove the plants offsite to make sure that it does not release viable seed.
Chemical control of Pigweed:
In Australia, a number of chemicals are registered for Pigweed, for instance: 2,4-D, Dicamba, Pendimethalin, Propyzamide, and Glyphosate but not all of these for turf use.
Pre-emergent Control.
If you use pre-emergent herbicides to control Purslane make sure they are present at the soil surface when seedlings emerge and are activated with an irrigation. If you treat mature Pigweed too late in the season, control is often erratic as seed set may have already occurred.
In the USA the pre-emergents herbicides Dithiopyr, Pendimethalin, and Propyzamide control Pigweed.
In Australia, Metolachlor is labelled for suppression of Pigweed. Another option is BASF Freehand herbicide.
Postemergent control
Dicamba, and 2,4-D are effective post emergent herbicides, and are available to the home gardener. Another option for Pigweed control is Quali-Pro Crest, but If you use this, use it with a Crop Oil Concentrate like ProForce Voltage MSO.
In South Africa, Casper Turf is registered to control Purslane or Pigweed at 600 – 800g /Ha.
Non Selective Control of Pigweed.
- Glufosinate-ammonium.
- Glyphosate. You can use Glyphosate as a non selective option to control Pigweed or Purslane. If you use Glyphosate, and water quality is an issue then use ProForce Manta Ray.
The following are non-selective but also have a long term residual and stop any re-growth of Pigweed.
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- Renegade. Renegade stops the germination of Purslane for up to 12 months, and reduces the need for multiple herbicide applications.
- Numchuk Quad. This gives effective post and pre emergent Purslane control for up to 12 months.
- Cortex Duo. Cortex Duo gives a rapid knockdown of Pigweed, and residual control for up to 3 months, and is safe to use around trees.
