Northern Prairie Wildlife Research Center
Southern Wetland Flora
Field Office Guide to Plant Species
Alternanthera phylloxeroides (Mart.) Griseb.
- Family: Pigweed (Amaranthaceae)
- Flowering: April-October
- Field Marks: This mat-forming species is distinguished by its smooth, opposite, toothless leaves
and its long-stalked spikes of small white flowers.
- Habitat: Wet to moist soils, forming mats over still water, including water-filled ditches, sloughs,
swales, bayous, lakes, ponds, canals.
- Habit: Perennial herb, forming mats.
- Stems: Trailing, mat-forming, smooth except for a few hairs where the leaves are attached;
flowering stems upright, up to 1 foot tall.
- Leaves: Opposite, simple, elliptic to oblanceolate, pointed or somewhat rounded at the tip,
tapering to the sessile base, smooth, toothless, somewhat fleshy, up to 4 inches long.
- Flowers: Small, crowded into terminal or axillary spikes; spike about 1/2 inch long, on a stalk
up to 3 inches long.
- Sepals: 4-5, white, free from each other, up to 1/4 inch long, minutely toothed near the tip.
- Petals: None.
- Stamens: 5, united at the base.
- Pistils: Ovary superior; styles 2.
- Fruits: Small, indehiscent, 1-seeded.
- Notes: This species, native in the tropics, can be an aggressive weed in wetlands. The flowers
have a sweetish odor.
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