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Simpson's primrose-willow

savannah primrose-willow

Habit Herbs sometimes creeping and rooting at nodes, new shoots arising from trailing stems or main caudex, rarely forming stolons.
Roots

fascicled, often fusiform, or spreading horizontally.

Stems

erect, ascending, decumbent, or prostrate, slightly ridged, well branched, 10–60(–75) cm, glabrous, with raised lines decurrent from leaf axils.

subterete to scarcely angled, with narrow raised lines or wings decurrent from leaf axils, 45–85 cm, branched mainly near base, glabrate with strigillose raised lines or strigillose.

Leaves

alternate or proximal pairs opposite;

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

petiole winged, 0.2–1 cm, blade spatulate or oblanceolate to very narrowly oblanceolate or sublinear, 0.6–1.5(–2) × (0.1–)0.3–0.7(–1.1) cm, base attenuate, margins subentire with hydathodal glands, apex acute or mucronate;

bracts not much reduced.

stipules narrowly deltate, 0.1–0.2 × 0.1–0.15 mm;

sessile;

blade ovate to obovate proximally, lanceolate-linear to linear distally, 2–7 × 0.2–1(–1.5) cm, base cuneate, margins entire, apex acute to rounded, surfaces strigillose, densely so particularly along veins;

bracts usually very reduced in size, sublinear.

Inflorescences

open, leafy spikes or racemes, flowers solitary in leaf axils;

bracteoles attached in opposite pairs near base of ovary, lanceolate-elliptic, 0.9–1.5(–2.5) × 0.4–0.9 mm, swollen at base, apex acuminate.

sparse racemes, flowers solitary in leaf axils;

bracteoles attached in subopposite pairs on distal 1/3 of pedicel, lanceolate-linear, 0.7–3.2(–5) ×0.2–0.5 mm, margins entire, apex acute, surfaces strigillose.

Flowers

sepals ascending, creamy white near base adaxially, ovate-deltate, 1.2–1.8 × 1–2 mm, margins entire, apex narrowly acute or acuminate, surfaces glabrous;

petals 0 or very rare;

filaments nearly translucent, 0.5–0.8 mm, anthers 0.2–0.4 × 0.3–0.4 mm;

pollen shed singly;

ovary obconic, subterete or scarcely 4-angled, 1.2–1.8 × 1.2–2 mm;

nectary disc elevated 0.3–0.4 mm on ovary apex, green, 0.9–1.3 mm diam., distinctly 4-lobed, glabrous;

style pale green, 0.4–0.6 mm, stigma pale yellow, subglobose, 0.2–0.3 × 0.2–0.3 mm, not exserted beyond anthers.

sepals strongly reflexed, narrowly ovate-deltate, 6–10 × 2.5–4.5 mm, margins entire, apex acute, surfaces finely strigillose to glabrate;

petals cordate, 14–19 × 13–15 mm, base attenuate, apex emarginate;

filaments opaque white, awl-shaped, 1.9–4.2 mm, anthers 2–4 × 0.6–1 mm;

ovary subcuboid to globose, 3–4 × 3–4 mm;

nectary disc elevated, domed, 0.8–1.4 mm diam., prominently 4-lobed, ringed with silky-curly hairs;

style 5–9.5 mm, glabrous, stigma capitate to hemispherical, 0.6–1.3 × 1.3–2.6 mm, shallowly 4-lobed, as long as or exserted beyond anthers.

Capsules

obconic, obscurely 4-angled, 1.5–2.5 × 1.5–3 mm, hard-walled, dehiscent by loculicidal slits, pedicel 0–0.4 mm.

subglobose to ellipsoid, 3.5–6.8 × 3.3–4.3 mm, 4-angled, angles not developed into wings, pedicel 6.5–17 mm.

Seeds

light brown or brown, ellipsoid, 0.5–0.6 × 0.3–0.4 mm, surface cells transversely elongate, glabrous, occasionally covered by minute waxy hairs.

light brown, elliptic-oblong to reniform, 0.5–0.7 × 0.3–0.4 mm, surface cells elongate transversely to seed length or elongate parallel to length near raphe.

2n

= 48.

= 16.

Ludwigia simpsonii

Ludwigia virgata

Phenology Flowering Apr–Nov (year-round). Flowering summer.
Habitat Sandy, peaty ditches, open pineland swamps, edges of cypress swamps, tidal flats and nearby marshes, limestone sinks. Sandy savannas, pinelands, damp roadside ditches, margins of ponds, bogs, irrigated fields, usually within 75 miles of sea coast.
Elevation 0–50 m. (0–200 ft.) 0–300 m. (0–1000 ft.)
Distribution
from FNA
FL; MS; West Indies (Cuba, Jamaica)
from FNA
AL; FL; GA; MS; NC; SC; VA
[WildflowerSearch map]
[BONAP county map]
Discussion

Ludwigia simpsonii is a hexaploid species occurring primarily in Florida, with outlier populations in southern Mississippi, western Cuba, and Jamaica. The species grows frequently in close proximity to L. curtissii; it grows mainly along roadside ditches with other weeds, whereas L. curtissii grows in less disturbed habitats, and the two seldom occur side by side (C. I. Peng 1989). Peng (1988, 1989) suggested that the hexaploid (2n = 48) L. simpsonii and the diploid (2n = 16) L. microcarpa gave rise to L. curtissii, the only octoploid (2n = 64) in sect. Isnardia.

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

Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Isnardia Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Ludwigia
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. palustris, L. peploides, L. peruviana, L. pilosa, L. polycarpa, L. ravenii, L. repens, L. spathulata, L. sphaerocarpa, L. suffruticosa, L. virgata
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. palustris, L. peploides, L. peruviana, L. pilosa, L. polycarpa, L. ravenii, L. repens, L. simpsonii, L. spathulata, L. sphaerocarpa, L. suffruticosa
Synonyms L. cubensis, L. curtissii var. simpsonii Isnardia virgata
Name authority Chapman: Fl. South. U.S. ed. 2 repr. 2, 685. (1892) — (as simpsoni) Michaux: Fl. Bor.-Amer. 1: 89. (1803)
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