Horse Purslane (Trianthema portulacastrum Linn.)

• A short dormancy period. This allows multiple generations in a single growing season.
• It produces enormous numbers of seeds. This results in a large seed bank.
• A unique C4-CAM photosynthetic pathway.

After you read this, you will be able to:

• Identify Horse Purslane.
• Know the habitat of Black Pigweed.
• Know the best cultural and chemical options to control Horse Purslane.

Black Pigweed has allelopathic effects on seed germination, seedlings, and yield in soybeans.

For more information on weeds check out our weed ID Chart.

Horse purslane is a strong competitor. Research shows it results in significant losses for many agricultural crops.

Category: Broadleaf (Dicot).

Photosynthetic Pathway: C4 + CAM. In the daylight hours Crassulacean Acid Metabolism (CAM) stops evapotranspiration through the stomata. This is a survival mechanism to reduce water loss. This allows CAM plants to survive when water is in short supply. This allows Horse Purslane to survive dry spells, and recover quickly once water is available again.

Flower: Black Pigweed flowers are white, pink, or purple.

Height: Horse Purslane has a prostrate growth habit.

Leaf length: Black Pigweed leaves are 1 to 5 cm long, have purple edges, and a petiole. They are opposite, unequal, and the lower pair is smaller than the others. Leaves are ovate to almost circular, with slightly wavy margins.

Reproduction: After it emerges, Horse purslane grows vegetatively for 35 to 40 days. After this both vegetative and reproductive growth occur simultaneously. Horse purslane seeds germinate at 20°C to 45°C, with an optimum germination temperature of 35°C.

The seeds of Black Pigweed have no dormancy period, and emerge from soil depths of up to 1 cm. However, as seed depth increases, emergence declines. Horse Purslane flowers 20 to 30 days after seed germination.

Horse Purslane produces 52,000 seeds in its life. These have a hard coat, and persist for many years.

Comments: Horse Purslane is thick, and flat at the nodes. Its taproot is white or brown, and has fibrous hairs that reach to a soil depth of 30 to 50 cm. The stems are maroon-purple, hairy, and erect.

Horse Purslane is toxic to livestock.

Habitat: Horse Purslane grows in dry areas along roadsides, wastelands and in lawns. Seedlings prefer rich and moist soil but are sensitive to flooding.

You can control Horse Purslane by cultural and chemical means, but successful management of this weed is best with an integrated approach.

• Indian Research shows that pre-emergent application of oxadiazon, and Pendimethalin (ProForce Battalia) control Horse Purslane in crops.
• In Australia in pigeonpeas, Pendimethalin at 1.14 kg ai/Ha reduced Black Pigweed by 80 to 90%.
• Both of these results contrast with US work in peanuts, where Pendimethalin at 1.12 kg ai/Ha, Metalochlor at 1.4 kg ai/Ha or dimethenamid gives < 75% control.
• In Sweet Potato production in Australia, Black Pigweed is a priority weed. Pre-emergent options are Chlorthal Dimethyl and Metalochlor.
• Indaziflam is registered in the USA for this weed.
• BASF Freehand.

• Bentazone (Quali-Pro Nutmeg).
• 2,4-D
• Dicamba.
• In Florida Trifloxysulfuron (ProForce Recondo) controls Horse Purslane in sugarcane. Best results are if you apply this with a non ionic surfactant like OptiSpread 1000 at 0.25% v/v.

Non selective options for use on public rights of way and domestic and urban areas include Glyphosate (Rapid Fire 800) under APVMA Permit 9907. If you use glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.

Other non selective options include:

• Cortex Duo
• Renegade and
• Numchuk Quad.