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false loosestrife, large-flower primrose-willow, primrose willow, six petal water primrose, Uruguayan primrose-willow, water primrose

southern water purslane, spoon primrose-willow

Habit Herbs, subshrubs, or emergent aquatics, adventitious roots sometimes forming a thick mass 10–23 cm at submerged nodes, sometimes woody at base, white pneumatophores 5–10 cm often on submerged stems. Herbs creeping and rooting at nodes, often forming mats.
Stems

floating or creeping and ascending to erect, terete, 20–200(–400) cm, simple to densely branched apically, glabrous (floating) or sparsely to densely villous (emergent), sometimes villous only on inflorescence.

prostrate or decumbent and ascending distally, slightly ridged, well branched, 10–40cm, densely strigillose throughout.

Leaves

stipules ovate or deltate, 0.7–2 × 0.5–1.1 mm, not succulent, apex subacute, mucronate;

petiole flattened, 0.5–2(–2.5) cm;

blade narrowly oblanceolate, narrowly elliptic, or lanceolate to obovate or spatulate, (1.5–)4.2–10.7(–13.5) × (0.5–)0.8–3 cm, chartaceous, base cuneate or attenuate, margins entire, apex acute to obtuse, rounded or truncate, sometimes mucronate, surfaces not shiny, usually glabrous, sometimes villous on petiole and veins or throughout;

bracts not 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.

Inflorescences

emergent stems sometimes in leafy racemes, sometimes reflexed, flowers solitary in leaf axils;

bracteoles obovate to narrowly obovate, 1–1.8 × 0.7–0.8 mm, apex acute or acuminate, attached on distal 1/2 of pedicel or at ovary base.

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.

Flowers

sepals ovate-deltate or lanceolate-deltate, (8–)12–19 × 2–5 mm, chartaceous, margins entire, apex acuminate, surfaces ± densely villous;

petals bright yellow, sometimes with orange base, fan-shaped, (15–)20–30 × (12–)16–25 mm, apex emarginate or mucronate;

stamens 10(or 12), in 2 unequal series, yellow, filaments recurved, shorter ones (1.6–)2.3–5.2 mm, longer ones (3.1–)3.6–7.5 mm, anthers oblong, (1.2–)1.7–4 × 1–1.5 mm;

ovary subcylindric, terete, 10–18 × 2–3 mm, apex ± broadened, glabrous or sparsely to densely villous;

nectary disc slightly raised on ovary apex, yellowish green, 2–4 mm diam., lobed, glabrous or ringed with white hairs;

style yellow, 6–10 mm, glabrous, stigma subcapitate-globose, 0.5–1.5 × 1.5–2.5 mm, often 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.

Capsules

cylindric or subclavate, terete, sometimes curved, (12–)16–24(–30)× 2.5–4 mm, with thick woody walls, irregularly and tardily dehiscent, pedicel (9–)13–25(–85) 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.

Seeds

embedded in wedge-shaped piece of endocarp, 0.8–1 × 0.8–1 mm.

dark reddish brown, ellipsoid, 0.5–0.7 × 0.4–0.5 mm, surface cells transversely elongate.

2n

= 80.

= 32.

Ludwigia hexapetala

Ludwigia spathulata

Phenology Flowering spring–late fall.
Habitat Wet places, along slow-moving rivers, streams, canals, ditches, often growing into main channel as aquatic weed.
Elevation 0–200[–2600] m. (0–700[–8500] ft.)
Distribution
from FNA
AL; AR; CA; FL; GA; KY; LA; MS; NC; NY; OR; PA; SC; TN; WA; Central America (Costa Rica); South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay) [Introduced in w Europe (Belgium, France, Spain)]
[WildflowerSearch map]
from USDA
[BONAP county map]
Discussion

Ludwigia hexapetala (2n = 80) was formerly included with L. grandiflora (2n = 48) in L. uruguayensis (Cambessèdes) H. Hara, and some authors (G. L. Nesom and J. T. Kartesz 2000) still consider them to be a single species. The small but consistent morphological differences and different ploidy levels argue for keeping them distinct at the species level.

Fernald described Jussiaea michauxiana (1944), since he thought that J. grandiflora Michaux (1803) was a homonym (not J. grandiflora Ruíz & Pavon). However, it was later determined that the volume containing the Ruíz & Pavon name was published in 1830 (not 1802) making the name by Michaux valid and legitimate, and the name by Fernald an illegitimate substitution. Plants now known as Ludwigia hexapetala were included in the circumscription of L. uruguayensis (Cambessèdes) H. Hara (based on J. uruguayensis Cambessèdes) by P. H. Raven (1963[1964]) and P. A. Munz (1965).

(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.)

Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Jussiaea 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. 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
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. sphaerocarpa, L. suffruticosa, L. virgata
Synonyms Jussiaeahexapetala hooker, J. repens var. major, L. grandiflora subsp. hexapetala, L. grandiflora var. hexapetala, L. uruguayensis var. major Isnardia spathulata
Name authority (Hooker & Arnott) Zardini, H. Y. Gu & P. H. Raven: Syst. Bot. 16: 243. (1991) Torrey & A. Gray: Fl. N. Amer. 1: 526. (1840)
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