Palmer Amaranth: Amaranthus palmeri
||Weed Description: An erect
summer annual that may reach 6 1/2 feet in height. Palmer amaranth closely resembles
many other pigweed species, and is found throughout the southern United States from
southern California to Virginia.
|Seedling: Stems below the cotyledons
(hypocotyls) are without hairs (glabrous) but may sometimes be slightly hairy, and are
often red in color. Cotyledons are narrow (10-12 mm long) and green to reddish in
color on the upper surface. Lower surfaces of cotyledons have a reddish tint.
First true leaves are alternate, ovate in shape, and are slightly notched at the tip of
the leaf blade (apex).
||Leaves: Alternate, without hairs
(glabrous), and lance-shaped or egg-shaped in outline. Leaves are 2 to 8 inches long
and 1/2 to 2 1/2 inches wide with prominent white veins on the undersurface. Leaves
occur on relatively long petioles.
that is often, but not always, reddish in color.
Fruit: A single seeded utricle that reaches 2 mm
in length and are wrinkled when dry. Each utricle splits open in the middle to
expose a single glossy black to dark brown seed that is 1 to 1.2 mm long.
|Stems: One central stem occurs from
which several lateral branches arise.
|Flowers: Small, green, inconspicuous
flowers are produced in dense, compact, terminal panicles that are from 1/2 to 1 1/2 feet
in length. Smaller lateral inflorescences also occur between the stem and the leaf
petioles (leaf axils). Male and female flowers occur on separate plants. Each
terminal panicle contains many densely packed branched spikes that have bracts that are 3
to 6 mm long.
||Identifying Characteristics: Dense,
compact terminal panicles and relatively tall plants with alternately arranged leaves with
petioles that are longer than the leaves. Palmer amaranth is often confused with
other similar pigweed species. However, no other pigweed species have terminal
panicles that reach 1 1/2 feet in length. Additionally, the terminal spike of palmer
amaranth is much smoother and narrower and less spike-like than either Redroot Pigweed (Amaranthus retroflexus) or smooth pigweed (Amaranthus
hybridus). The leaves of palmer amaranth are also without hairs and have
prominent white veins on the undersurface unlike those of redroot pigweed. These
species may also resemble Common Lambsquarters (Chenopodium
album) in the cotyledon stage, however common lambsquarter's cotyledons often have a
mealy gray cast and the first true leaves are alternate, unlike any of the pigweed