How to Manage Pests

Identification: Weed Photo Gallery

Pigweeds

Scientific name: Amaranthus spp. (Pigweed Family: Amaranthaceae)

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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.

Seedling

Seedlings of all common pigweeds are similar. Cotyledons (seed leaves) are long and narrow and are often red underneath.

Mature plant

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.

Flower

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).

Fruit

The single-seeded fruit 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

Seeds are round, roughly 1/25 to 1/17 inches (1–1.5 mm) in diameter, glossy, and dark reddish brown to black.

Reproduction

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 species/Similar looking plants

Redroot pigweed
Prostrate pigweed

More information

• Broadleaf ID illustration
• Palmer amaranth Calflora's distribution map
• Smooth pigweed Calflora's distribution map
• Low amaranth Calflora's distribution map
• Redroot pigweed Calflora's distribution map
• Tumble pigweed Calflora's distribution map
• See UC IPM's Pest Management Guidelines for agricultural information