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Green Pigweed

Amaranthus powellii S. Wats.


Family: Amaranthaceae

Habit: summer annual

Habitat: Important weed of agronomic crops and gardens. Become problematic in the northeastern US and Canada only in the past 50 years or so.

Similar Species: Redroot pigweed (Amaranthus retroflexus) has wavy leaf margins and an upper stem that is very hairy whereas Powell amaranth has entire leaf margins and upper stems lacking hairs. Also, redroot pigweed flowers are held in short, thick terminal branched spikes and not in elongated, stiff, mostly unbranched spikes as for Powell amaranth. Seedlings of the two species are difficult to differentiate and the presence of a reddish-pink root is not a reliable characteristic for differentiating redroot pi


Ecology

Management:

Because Powell amaranth seedlings are very small and fragile, stirring of the top 1-2 inches of soil 2 to 4 times within the first month following tillage is highly effective at removing most of the individuals that will emerge during the season (Weed early & shallow). Mulches of organic materials are highly effective for suppressing Powell amaranth, but it is often best to reduce plant density by superficial weeding before placing the mulch. Dense planting helps control this weed in crops that will tolerate high density.

Because the seeds are persistent in the soil, removal of escapes from the garden before they set seeds is critical for long term control.

Useful Management Techniques