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wing primrose-willow

Habit Herbs with aerenchyma when base submerged, forming stolons from lower nodes, 8–65(–95) cm, 0.7–2.5 mm thick.
Stems

erect or somewhat sprawling, slightly to distinctly winged (wings to 1.8 mm wide), branched distally, 40–120(–160) cm, glabrous.

Leaves

alternate;

stipules ovate-deltate, often narrowly so, 0.2–0.4 × 0.1–0.3 mm, succulent;

stolons: petiole 0.15–1 cm, blades orbiculate to oblanceolate or broadly elliptic, 0.4–2.6 × 0.4–1.5 cm, base attenuate, apex rounded to subacute;

stems: petiole 0–0.3 cm, blade lanceolate-elliptic or very narrowly elliptic to linear, sometimes to oblanceolate or oblanceolate-elliptic near base, 1.8–10 × 0.2–1.3(–2) cm, base narrowly cuneate or attenuate, margins subentire with remote hydathodal glands, rarely minutely papillose-serrulate near apex, apex acute to narrowly acute, leaves on side branches much reduced;

bracts much reduced.

Inflorescences

sometimes congested, leafy spikes or racemes, flowers solitary in distal leaf axils;

bracteoles attached near base of ovary, lanceolate-elliptic or narrowly so, 2.4–4.7 × 0.6–1.5 mm, margins minutely papillose or smooth, apex acute, surfaces glabrous.

Flowers

sepals spreading to reflexed, creamy white adaxially, broadly ovate-deltate, 2–4 × 1.6–4 mm, margins smooth or minutely papillose-serrulate, apex acute or acuminate, surfaces glabrous;

petals 0;

filaments nearly translucent, 1.1–1.7 mm, slightly dilated near base, anthers 0.5–0.9 × 0.4–0.7 mm;

pollen shed singly;

ovary obpyramidal, sharply 4-angled, 2–3.8 × 2–3.5 mm;

nectary disc elevated 0.5–0.8 mm on ovary apex, bright yellow, square with rounded corners, 2–3.3 mm diam., prominently 4-lobed, glabrous;

style pale green, 0.8–1.3 mm, glabrous, stigma pale yellow, subglobose, 0.3–0.6 × 0.3–0.7 mm, shallowly 4-lobed on top, not exserted beyond anthers.

Capsules

obpyramidal, sharply 4-angled and 4-winged, 3–5 × 2.8–4.5 mm, with hard walls somewhat bulging, dehiscent by apical ring, pedicel 0–0.8 mm.

Seeds

light brown, ellipsoid, slightly curved on both ends, 0.6–0.7 × 0.3–0.4 mm, surface cells elongate transversely to seed length.

2n

= 48.

Ludwigia alata

Phenology Flowering Jun–Oct.
Habitat Ditches, edges of ponds and lagoons, peaty or sandy swales, open cypress swamps, sandy borrow pits in open pine woods, swampy, flat outcrops of oolitic rocks, wet savannas, tidal flats, brackish marshes, sandy beach strands and hammocks.
Elevation 0–50 m. (0–200 ft.)
Distribution
from FNA
AL; FL; GA; LA; MS; NC; SC; VA; West Indies (Jamaica)
[BONAP county map]
Discussion

Ludwigia alata occurs only at very low elevations along the Atlantic and Gulf coastal plains from Virginia to the tip of Florida, and west to southwestern Louisiana, with disjunct populations on Jamaica (C. I. Peng 1989). This hexaploid species is often confused with L. lanceolata, with which it shares two genomes (Peng 1988, 1989) and with which it is frequently sympatric. The showy petals of L. alata suggest a higher level of outcrossing, and numerous natural hybrids have been documented (Peng 1988, 1989).

(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. 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. palustris, L. peploides, L. peruviana, L. pilosa, L. polycarpa, L. ravenii, L. repens, L. simpsonii, L. spathulata, L. sphaerocarpa, L. suffruticosa, L. virgata
Synonyms Isnardia alata
Name authority Elliott: Sketch Bot. S. Carolina 1: 212. (1817)
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