Ludwigia polycarpa
Ludwigia spathulata
false loosestrife, many-fruit water-primrose, manyfruit primrose-willow
southern water purslane, spoon primrose-willow
erect or ascending, slightly ridged, well branched, (10–)25–60(–85) cm, glabrate with raised ± strigillose lines decurrent from leaf axils.
prostrate or decumbent and ascending distally, slightly ridged, well branched, 10–40cm, densely strigillose throughout.
alternate;
stipules narrowly to broadly ovate, 0.1–0.4 × 0.1–0.3 mm;
stolons: leaves often clustered near apex of stolon, petiole 0–0.5 cm, blade narrowly elliptic or oblanceolate, 0.8–2(–3.2) × 0.2–0.8(–1.2) cm, base attenuate, margins entire or remotely denticulate, apex acute, surfaces glabrous;
stems: petiole winged, 0.1–1 cm, blade very narrowly oblong-elliptic, 3.5–11 × 0.4–1(–1.7) cm, base very narrowly cuneate or long-attenuate, margins entire and densely, minutely papillose-serrulate with obscure hydathodal glands, apex narrowly acute or acuminate, surfaces glabrous;
bracts not much reduced.
opposite;
stipules narrowly deltate or ovate, 0.05–0.15 × 0.05–0.1 mm;
petiole very narrowly winged, 0.3–0.9 cm, blade elliptic-spatulate or narrowly so, 0.9–1.7 × 0.3–0.9 cm, base attenuate, margins entire, apex acute, surfaces strigillose;
bracts not reduced except at branch tips.
elongated, leafy spikes, flowers solitary in leaf axils, sometimes borne almost to base of stems;
bracteoles attached 0.5–2.5(–3) mm distal to base of ovary, linear-lanceolate, 3.5–6.5(–8) × 0.
leafy spikes or racemes, flowers usually paired in leaf axils;
bracteoles attached at base of ovary or on short pedicel, narrowly oblong or oblanceolate, 0.2–0.8 × 0.05–0.2 mm, apex acute, often obscured by hairs.
sepals spreading horizontally with reflexed tips, pale green, narrowly ovate-deltate, 2.5–4.5 × 1.5–3.2 mm, margins entire, minutely papillose-serrulate, apex elongate-acuminate, surfaces glabrous;
petals 0;
filaments yellowish green, 0.7–1.5 mm, base dilated, anthers 0.5–0.9 × 0.5–0.7 mm;
pollen shed in tetrads;
ovary oblong, barely 4-angled, 3–4.5 × 2–3.5 mm;
nectary disc elevated 0.5–0.8 mm on ovary apex, yellowish green, 1.8–3 mm diam., 4-lobed, glabrous;
style yellowish green, 0.5–0.8 mm, glabrous, stigma broadly clavate to subglobose, 0.4–0.8 × 0.3–0.6 mm, usually 4-lobed, not exserted beyond anthers.
sepals ascending, pale green, broadly ovate-deltate, 1–1.7 × 1.1–1.7 mm, margins entire, apex acuminate, surfaces densely strigillose;
petals 0;
filaments translucent, 0.5–0.8 mm, anthers 0.2–0.4 × 0.3–0.5 mm;
pollen shed singly;
ovary oblong-obovoid, 4-angled to subterete, 1.5–2.5 × 1–1.5 mm;
nectary disc elevated 0.1–0.2 mm on ovary apex, yellowish green, 0.7–0.9 mm diam., 4-lobed, glabrous;
style yellowish green, 0.3–0.5 mm, glabrous, stigma pale yellow, capitate, 0.2–0.3 × 0.2–0.3 mm, not exserted beyond anthers.
oblong-obovoid, obscurely 4-angled, 4–7 × 2.5–5 mm, hard-walled, irregularly dehiscent, pedicel 0.1–0.3 mm.
oblong-obovoid, subterete, 2.5–4(–4.5) × 1.5–2.5 mm, thin-walled, seeds often visible on exocarp as small bumps, irregularly dehiscent or dispersing as unit, pedicel 0–0.5 mm.
light brown, narrowly oblong with curved ends, 0.5–0.6 × 0.2–0.3 mm, surface cells elongate parallel to seed length.
dark reddish brown, ellipsoid, 0.5–0.7 × 0.4–0.5 mm, surface cells transversely elongate.
–1(–1.3) mm, with a swollen base, margins minutely papillose-serrulate.
= 32.
= 32.
Ludwigia polycarpa
Ludwigia spathulata
Ludwigia polycarpa, unlike all other species in sect. Isnardia, is distributed primarily in the central Midwest and Great Lakes regions, with one highly disjunct population recorded from Kootenai County, Idaho, which is presumably introduced. This species has also been found scattered as far east as Connecticut and Massachusetts, and reports of it from Arkansas, Maine, Tennessee, and Vermont cannot be confirmed. As indicated by C. I. Peng (1989), a report of this species from Alabama involved a natural hybrid between L. glandulosa and L. pilosa.
The basal stolons formed by Ludwigia polycarpa tend to be shorter, more condensed, and more branched than those found in other species, and may be a morphological adaptation to perennial survival in the colder areas in which it grows.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Flowers May–Sep. Ditches, swales, edges of ponds, lakes, sinks, swamps, sandy river bars, dried seasonal ponds, disturbed low savannas; of conservation concern; 0–200 m; Ala., Fla., Ga., S.C.
The tetraploid Ludwigia spathulata is relatively uncommon and occurs primarily on the Gulf Coastal Plain in the panhandle of Florida, southern Alabama, and southwestern Georgia. Outlying populations have also been collected in transitional areas between the Coastal Plain and the Piedmont in South Carolina and Georgia. With its small apetalous flowers, L. spathulata is modally autogamous and shows low morphological variability. Its strongest affinities appear to be with L. palustris, with which it shares a genome (C. I. Peng 1988, 1989).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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