This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Ludwigia hirtella Raf. Med. Rep. (II.) 5: 358. 1808.
Erect, branching, hirsute-pubescent, 1°-2° high, the clustered roots spindle-shaped. Leaves alternate, oblong-lanceolate or ovate-lanceolate, sessile, obtuse or acutish at the apex, rounded at the base, 1'-1 1/2' long; pedicels 2-bracteolate; flowers axillary, solitary, pedun-cled, 6"-10" broad; calyx-lobes ovate-lanceolate, acute, somewhat shorter than the yellow petals; capsules cubic with a rounded base, hirsute, about 2 1/2" high, shorter than the calyx-lobes, opening by an apical pore.
Ludwigia alternifolia L. Sp. Pl. 118. 1753.
Erect, branching, glabrous or finely pubescent, 2°-3i° high. Leaves alternate, short-petioled, lanceolate to linear-lanceolate, acute or acuminate at the apex, narrowed at the base, 2'-4 1/2' long; flowers axillary, short peduncled, solitary, 6"-8" broad; peduncles 2-bracted above the middle; calyx-lobes ovate to ovate-lanceolate, acuminate, about equalling the yellow petals which fall away when the plant is shocked; capsules glabrous, cubic with a rounded base, slightly wing-angled, about 2 1/2" high, opening by a pore at the base of the style and finally loculi-cidally dehiscent.
In swamps, New Hampshire to northern New York, Ontario, Michigan. Kansas, Florida and Texas. Roots often tuberous. June-Sept.