Pigweeds (Amaranthus spp.)
Click on images to enlarge
Pigweeds are erect summer annual plants that germinate from seeds during late winter through summer. Several species occur, but the most common is redroot pigweed.
Seedlings of all common pigweeds are similar. Cotyledons (seed leaves) are long and narrow and are often red underneath.
Prostrate pigweed (bottom, right in photo) forms dense mats, has dark glossy green leaves with distinctive light colored edges, and often pink or red tinged stems. Tumble pigweed is bushy with light green leaves.
Tumble pigweed (top, left) flower clusters only grow between the stem and leaf stalks, rather than in spikes as found in other pigweeds such as palmer amaranth (top, right).
The single-seeded fruits are tiny capsules, roughly less than 1/17 of an inch (1.5 mm) long and open around the middle by a caplike lid to release the seed.
Seeds are round, roughly 1/25 to 1/17 inches (1–1.5 mm) in diameter, glossy, and dark reddish brown to black.
In general, pigweeds reproduce by seed. In low amaranth, new shoots can grow from upper portions of a taproot and crown that remain in the soil after cultivation.
Related or similar plants
- Redroot pigweed, Amaranthus retroflexus
- Prostrate pigweed, Amaranthus blitoides