Hygrophila costata Nees & T. Nees

Gulf Swampweed

Herb

Perennial

Vascular

Gulf Swampweed is a native perennial in the Acanthus family (Acanthaceae). It can be found in the southern half of Alabama. Gulf Swampweed is native from the southern United States south through Central and South America, and in introduced in Australia and other warm parts of the world. It grows in shallow water at the edges of rivers and streams, in swamps, and on the margins of ponds and lakes. Gulf Swampweed is an emergent herbaceous perennial. Young shoots are often somewhat four angled. Older stems are more rounded and are reddish-purple in color. The stems are slightly pubescent and succulent. Stems produce adventitious roots at the nodes. Floating stems can be more than 1 meter in length. The leaves are opposite, oblong to elliptic in outline, with entire or undulate margins. Leaves are slightly pubescent below and have acuminate (pointed) tips and attenuate (gradually narrowed) bases. Leaves may be sessile or have short petioles. Inconspicuous flowers are produced in cymes in the leaf axils. The flowers are tubular and two-lipped. The upper lip is two lobed and the lower lip is three lobed. The flowers are white in color and very delicate. The flowers seldom last more than a few hours before turning brown. The fruit is a fusiform (spindle shaped) capsule with 12-18 round seed. The seed are brown in color and sticky when wet. Gulf Swampweed is available from nurseries specializing in aquatic plants for aquariums and pools. It is considered an invasive weed in Australia, where it was introduced through the aquarium plant trade.--A. Diamond

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Native OBL (NWPL) OBL (DEP) G5 (Global Rank)

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