Prostrate Pigweed (A) — Amaranthus blitoides — Family: Amaranthaceae — Amaranth

Prostrate pigweed is a native mat-forming summer annual weed that invades thin, damaged or under-fertilized lawns. It is common in areas with disturbed soils or neglected areas. Prostrate pigweed lacks the hairs common to redroot pigweed and has smooth leaves.

Also Known As...

• spreading pigweed
• prostrate amaranth
• mat amaranth

Lanceolate	Entire	Opposite	Spreading

leaves are spatulate (tapering to the petiole) to obovate (wider at the apex); leaves are thin, pale-green and glossy with prominent veination

prostrate stems with upright tips

primary taproot with secondary, more fibrous roots

flowers form in small axillary cluster of leaves (no terminal spikes)

Prostrate pigweed can be confused with other members of the Amaranth family. It is important to remember that prostrate pigweed is glabrous (no hairs) and does not produce terminal seed spikes. The flowers on prostrate pigweed will be in axillary clusters. The leaves on prostrate pigweed have smooth margins (entire). The leaves on redroot pigweed are ovate (wider at the base) and have wavy margins.

Links:

• Redroot Pigweed (Amaranthus retroflexus)

Prostrate pigweed is a small-seeded summer annual weed that needs soil disruption to expose the seed and encourage germination. Prostrate pigweed is most common in new establishments where the turfgrass is not very dense or competitive. It can be difficult to remove prostrate pigweed with mowing due to its low growth habit. It will not persist more than one season if the turf is encouraged to fill-in during the fall after the pigweed has completed its lifecycle. Prostrate pigweed re-establishes by seed each season. For this reason, it is unlikely that redroot pigweed will invade a thick vigorous turf in the year after establishment. This is a case where improved turfgrass vigor and density is extremely effective at limiting future populations.

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