Ludwigia hyssopifolia (G.Don) Exell

Annual herb 5 cm to 3 m, often becoming woody at the base; young growth and inflorescence minutely puberulent; elongate aerophores arising from buried submerged roots. Leaves lanceolate, 1-9 by 0.2-3 cm, narrowly cuneate at the base, apex acuminate; nerves 11-17 pairs; submarginal vein not prominent; petiole 2.5-18 mm. Sepals 4, lanceolate, 2-4 by 0.7-1.2 mm, finely puberulent, 3-nerved. Petals yellow, fading orange-yellow, elliptic, 2-3 by 1-2 mm. Stamens 8, pale greenish yellow, epipetalous ones shorter; filaments of episepalous stamens 1-2 mm, those of epipetalous ones 0.5-1 mm; anthers 0.4-0.6 mm wide, 0.2-0.3 mm high, shedding pollen directly onto the stigma at anthesis. Pollen grains shed singly. Disk ± elevated, with a depressed ciliate nectary surrounding the base of each epipetalous stamen. Style pale greenish yellow, 1-1.5 mm; stigma depressed-globose, c. 0.6-1.2 mm ø, 0.5-0.8 mm high, shallowly 4-lobed, the upper portion receptive. Capsule relatively thin-walled, finely puberulent, 1.5-3 cm by 1-1.2 mm, subterete, enlarged in the upper 1/6 to ⅓, subsessile. Lower seeds uni-seriate in each cell of the capsule, nearly vertical, brown, oblong, 0.7-0.85 mm long, each firmly embedded in a cube of relatively hard endocarp; raphe ⅓ the diameter of the body. Seeds in upper inflated portion of the capsule multiseriate, free, ovoid, 0.35-0.5 mm long, paler brown than the lower seeds and with a narrower raphe. Lower part of capsule at first marked by distinct bumps corresponding to the position of the uniseriate seeds, but as the endocarp hardens and swells, the capsule becomes smooth. Gametic chromosome number, n = 8.

A very common weed of pools, along drains, shallow ditches, water and river edges, in paddies and humid, fallow garden land, on waste land, fallow sawahs, and in clearings, both on clay and humid white sand (Borneo), in pools in Eucalypt savannah (Wetar I.), on Mt Kelud (Central Java) as a pioneer on old volcanic mudstreams (lahars), from the plains up to c. 1000 m. Fl. Jan.-Dec.

Uses. HEYNE ( HEYNE Nutt. Pl. 1927 1206 ) noted that in N. Celebes it is used for poulticing pimples. According to BURKILL ( BURKILL Diet. 1935 1273 ) it is in Malaya generally stocked by Chinese herbalists, but its use is not clear; it was once recorded that an infusion of the root is swallowed by Malays for syphilis. In the Philippines the whole plant is used for black dye ( QUISUMBING Medic. Pl. Philip. 1951 676 ).

Can be grown by seedlings.