This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seeds and by rooting at the joints. Time of bloom: June to October. Seed-time: July to November. Range: Nova Scotia to Manitoba and Oregon, southward to
Florida, Louisiana, California, and Mexico. Habitat: Swamps, wet meadows; clogs ditches.
A small, prostrate, often floating weed, whose habit of putting forth fibrous roots at its joints makes it frequently a pest to the muck farmer.
Stems smooth, succulent, much branched at the base, often ruddy-colored, four to fifteen inches long. Leaves opposite, ovate or spatulate, a half-inch to an inch long, narrowing to a short, slim petiole; when growing in mucky ground, they are smaller, nearly sessile, blunt-pointed, and reddish. Flowers axillary, sessile, solitary, scarcely a tenth of an inch broad; they have a top-shaped calyx with four pointed triangular lobes, and sometimes four small reddish petals, though these are often wanting, particularly in floating plants; stamens four and stigma four-parted; ovary four-celled. Capsule four-sided and four-celled, flat at the top, containing many very fine, wrinkled, brown seeds.
Fig. 204.- Seed-box (Ludvigia alterni-folia). X 1/4.
Only by digging or hand-pulling can this obnoxious little plant be removed, and the work needs to be done early, before the first development of seed.