Pigweed, Green, Amaranthus powellii

Life Cycle

Annual.

Propagation

Reproducing only by seed.

Stems

Stems are green to reddish, erect, up to 1.5 m tall, simple or branched and often less hairy than that of redroot or smooth pigweed, with the majority of hair occurring at the highest internode.

Leaves

Alternate (1 per node), with the first leaves of green pigweed being tapered towards the tip , compared to those of redroot and smooth pigweed which have a more ovate or round shape. Leaf tips have a shallow notch. Margins are smooth and sometimes wavy. Older leaves of green pigweed are a very distinctive shiny green colour.

Flowers and Fruit

Compared to Redroot pigweed, older plants of Green pigweed have a brighter green, thinner, looser inflorescence in which the individual bristly, finger-like spikes (a) are usually longer (4-12cm) and tend to point upwards. The terminal spike (b) is much longer, narrower, about 1-1.5cm thick, and either stands erect or frequently hangs over a bit. Flowers and flower bracts are about the same length as in Redroot pigweed, but male flowers usually have only 3 stamens, and the chaff-like sepals are broadest at or below the middle and taper towards the tip. Compared to Smooth pigweed, older plants have thicker, spinier spikes and slightly larger flowers. Flowers from July to September.

Habitat

Green pigweed occurs throughout southern Ontario but is more abundant in the southwest, in some areas it is probably more important than Redroot pigweed.

Distinguishing Features

- young plants distinguished from Redroot pigweed by their somewhat shiny green or slightly reddish-green colour and somewhat less hairy stem and leaves. - compared to redroot pigweed, green pigweed has brighter green, thinner and looser inflorescence. Individual bristly, finger-like spikes are usually longer and tend to point upwards


Figure #1.

Green pigweed. A. Base of plant. B. Top of flowering plant.


Figure #2.

Young green pigweed plants are distinguished from redroot pigweed by their somewhat shiny green or slightly reddish-green colour.


Figure #3.

Green pigweed leaf top.


Figure #4.

Green pigweed leaf bottom.


Figure #5.

Upper stem of green pigweed.


Figure #6.

Green pigweed seed head. Brighter green, thinner, looser inflorescence than redroot pigweed.