Horse purslane (Trianthema portulacastrum Linn.)

• A low dormancy period. This allows multiple generations in a single growing season.
• Enormous seed production which results in a large seed bank.
• Its 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 negative allelopathic effects on seed germination, seedlings, and productivity in soybeans.

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

Horse purslane is a strong competitor. Research shows it reduces mung bean yield by 50 to 60%, and significant losses in other crops are also attributed to this weed.

Category: Broadleaf (Dicot).

Photosynthetic Pathway: C4 + CAM. In the day Crassulacean Acid Metabolism (CAM) stops evapotranspiration through a plants stomata (water loss). This allows CAM plants to survive when water is limiting plant growth. Horse Purslane survives dry spells, and recovers quickly when water is available again.

Flower: Flowers are white, pink, or purple.

Height: Horse Purslane has a prostrate growth habit.

Leaf length: The leaves of Black Pigweed are 1 to 5 cm long, are purplish along their edges, and have 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, and then both vegetative growth and reproductive growth occur simultaneously. Horse purslane seeds germinate at 20°C to 45°C, with an optimum germination at 35°C.

The seeds of Black Pigweed have no dormancy and will emerge from a depth of 1 cm. However, emergence declines with increasing soil depth. Horse Purslane starts to produce flowers 20 to 30 days after germination of the seeds.

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 with fibrous hairs that reach to a depth of 30 to 50 cm. Stems are maroon-purple, hairy, and erect.

Horse Purslane is toxic if ingested.

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 can only be achieved by an integrated approach.

• Indian Research shows that pre-emergent application of oxadiazon, and Pendimethalin (ProForce Battalia) effectively control Horse Purslane in various crops.
• In Australia in pigeonpeas, Pendimethalin was applied at 1.14 kg ai/Ha and reduced Horse Purslane biomass by 87% and 92%.
• Both of these results contrast with US work in peanuts, where Pendimethalin at 1.12 kg ai/Ha and Metalochlor at 1.4 kg ai/Ha gave < 75% control.
• In Sweet Potato production in Australia, Black Pigweed is a priority weed. Pre-emergent options are Chlorthal Dimethyl and Metalochlor.
• Esplanade.
• S-metolachlor, or dimethenamid applied alone only gives less than 75% control of Horse Purslane.

• Bentazone (Quali-Pro Nutmeg)
• 2,4-D
• Dicamba.
• In Florida Trifloxysulfuron (ProForce Recondo) is the only herbicide labeled for selective control of Horse Purslane in sugarcane. Use 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.

• Cortex Duo and
• Numchuk Quad.