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common water-primrose, eastern false loosestrife, ludwigie palustre, marsh primrose-willow, marsh purslane, marsh seedbox, water-purslane

Habit Herbs often creeping, rooting at nodes, forming mats.
Stems

prostrate or decumbent and ascending at tips, subterete or with raised lines decurrent from leaf axils, well branched, 10–50(–70) cm, glabrous or, sometimes, minutely strigillose on leaf margins and inflorescence.

Leaves

opposite;

stipules narrowly deltate, 0.05–0.1 × 0.05–0.1 mm;

petiole narrowly winged, 0.1–2.5 cm, blade narrowly to broadly elliptic or ovate-elliptic, 0.5–4.5 × 0.3–2.3 cm, base abruptly attenuate, margins entire and minutely strigillose, apex subacute, surfaces glabrous;

bracts not reduced.

Inflorescences

leafy spikes or racemes, flowers usually paired in leaf axils of prostrate stems;

bracteoles attached at base or to 2.5 mm distal to base of ovary, sublinear, 0.3–1(–1.8) × 0.1–0.8 mm.

Flowers

sepals ascending, green, ovate-deltate, 1.1–2 × 1–2.1 mm, margins finely serrulate with minute hairs, apex acuminate, sometimes with blunt tip, surfaces glabrous;

petals 0;

filaments translucent, 0.4–0.6 mm, anthers 0.2–0.4 × 0.3–0.6 mm;

pollen shed singly;

ovary oblong, 1.5–3.5 × 1–2 mm, glabrate;

nectary disc elevated 0.15–0.3 mm on ovary apex, green, 1–2 mm diam., 4-lobed, glabrous;

style pale green, 0.3–0.7 mm, glabrous, stigma subglobose or capitate, 0.4–0.6 × 0.2–0.4 mm, not exserted beyond anthers.

Capsules

oblong obovoid, 4-angled, (1.6–)2–5 × 1.5–3(–3.5) mm, thin-walled, irregularly dehiscent or dispersing as unit, pedicel 0–0.5 mm.

Seeds

yellowish brown, ellipsoid, 0.5–0.7 × 0.3–0.4 mm, surface cells transversely elongate.

2n

= 16.

Ludwigia palustris

Phenology Flowering Feb–Oct.
Habitat Roadside ditches, wet meadows, dried pond bottoms, margins of ponds, swamps, rivers, alluvial sand bars.
Elevation 0–1000[–2700] m. (0–3300[–8900] ft.)
Distribution
from FNA
AL; AR; AZ; CA; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NM; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; BC; NB; NF; NS; ON; QC; Mexico (Chiapas, Chihuahua, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nuevo León, Oaxaca, San Luis Potosí, Sinaloa, Sonora, Tamaulipas, Veracruz); West Indies (Cuba, Hispaniola, Jamaica, Puerto Rico); Bermuda; Central America (Costa Rica, Guatemala, Panama); South America (Colombia, Peru, Venezuela); Europe; sw Asia; Africa; intro­duced in Pacific Islands (Hawaii, New Zealand); Australia
[WildflowerSearch map]
[BONAP county map]
Discussion

Ludwigia palustris is a common diploid and most widely distributed species in sect. Isnardia. It is particularly widespread in temperate North America and in Europe [the type is thought to be from Europe (P. H. Raven 1963[1964]; C. I. Peng et al. 2005)], more sporadically in Africa and sw Asia, and introduced in Australasia, and Hawaii. The close sister relationship of sect. Isnardia with sect. Miquelia (L. ovalis Miquel only, endemic to eastern Asia) suggests that this clade may have had a history connected with the evolution of the Arcto-Tertiary Geoflora (P. H. Raven and D. I. Axelrod 1974; Peng et al.).

Ludwigia palustris is known to hybridize with L. brevipes producing the sterile L. ×lacustris Eames.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Isnardia
Sibling taxa
L. alata, L. alternifolia, L. arcuata, L. bonariensis, L. brevipes, L. curtissii, L. decurrens, L. erecta, L. glandulosa, L. grandiflora, L. hexapetala, L. hirtella, L. lanceolata, L. leptocarpa, L. linearis, L. linifolia, L. maritima, L. microcarpa, L. octovalvis, L. peploides, L. peruviana, L. pilosa, L. polycarpa, L. ravenii, L. repens, L. simpsonii, L. spathulata, L. sphaerocarpa, L. suffruticosa, L. virgata
Synonyms Isnardia palustris, I. ascendens, I. nitida, I. palustris var. americana, L. apetala, L. nitida, L. palustris var. americana, L. palustris var. inundata, L. palustris var. liebmannii, L. palustris var. nana, L. palustris var. pacifica
Name authority (Linnaeus) Elliott: Sketch Bot. S. Carolina 1: 211. (1817)
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