Ludwigia hexapetala |
Ludwigia decurrens |
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false loosestrife, large-flower primrose-willow, primrose willow, six petal water primrose, Uruguayan primrose-willow, water primrose |
wingleaf primrose-willow |
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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 annual or short-lived perennial, roots and lower stem sometimes inflated and spongy. |
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. |
erect or strongly ascending, sharply 4-angled and 4-winged, 30–200 cm, simple to densely branched, glabrous. |
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. |
stipules deltate, 0.4–0.5 × 0.2 mm; sessile and continuous with wings on stem; blade lanceolate or narrowly lanceolate to narrowly ovate or elliptic, 2–20 × 0.2–5 cm, base acute or rounded, margins entire, often minutely scabrid, apex acute or acuminate, membranous, surfaces glabrous or sometimes minutely puberulent on abaxial veins; bracts linear, mostly reduced. |
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. |
open, leafy racemes, flowers solitary in distal axils; bracteoles deciduous, usually attached near base of ovary, without subtending glands, lanceolate to subovate, 0.5–1 × 0.2–0.5 mm, apex acute. |
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 ovate to lanceolate, 7–12 × 1.5–4 mm, apex acute or short acuminate, membranous, margins usually minutely scabrid, surfaces usually glabrous, sometimes puberulent abaxially; petals orbiculate-obovate, 10–20 × 10–18 mm, short-clawed; stamens 8 in 2 subequal series, yellow, filaments 1.3–2.5 mm, anthers oblong, 1.3–1.6 × 0.5–0.6 mm; ovary obconic, sharply 4-angled and 4-winged, 6–10 × 2–4.5 mm, glabrous or minutely puberulent; nectary disc plane on ovary apex, 3–5 mm diam., 4-lobed, glabrate or ringed with short hairs; style 2.5–3.2 × 0.5–0.6 mm, stigma globose, 1–2 × 1–2 mm, not exserted beyond anthers and pollen shed directly on it. |
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. |
rarely sharply curved, subclavate to oblong-obovoid or narrowly obpyramidal, sharply 4-angled and 4-winged, 10–25 × 3–5 mm, glabrous, pedicel 2–15 mm. |
Seeds | embedded in wedge-shaped piece of endocarp, 0.8–1 × 0.8–1 mm. |
oblong or subcylindric, 0.5–0.6 × 0.2 mm, striate, raphe very narrow and inconspicuous. |
2n | = 80. |
= 16. |
Ludwigia hexapetala |
Ludwigia decurrens |
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Phenology | Flowering spring–late fall. | Flowering summer–early fall. |
Habitat | Wet places, along slow-moving rivers, streams, canals, ditches, often growing into main channel as aquatic weed. | Moist or swampy habitats along sloughs, muddy stream banks, marshy shores of lakes and ponds, ditches, swamps. |
Elevation | 0–200[–2600] m. (0–700[–8500] ft.) | 0–300[–600] m. (0–1000[–2000] ft.) |
Distribution |
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)]
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AL; AR; DC; FL; GA; IL; KY; LA; MD; MO; MS; NC; OH; OK; PA; SC; TN; TX; VA; WI; WV; Central America; South America; Mexico (Campeche, Chiapas, Michoacán, Tabasco); West Indies; Bermuda [Introduced in Europe (France), e Asia (Japan), Africa (Cameroon), Pacific Islands (Philippines)]
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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.) |
Ludwigia decurrens appears to be most closely related to L. erecta, differing by having winged, not angled, capsules and larger flowers, with sepals 7–12 mm and petals 10–20 mm (in L. erecta, sepals 3–6 mm, petals 3.5–5 mm). They often grow in close proximity and may hybridize, but hybrids would be difficult to detect. Ludwigia decurrens is often self-pollinating, but larger flowers may promote outcrossing. Ludwigia jussiaeoides Michaux is an illegitimate later homonym of L. jussiaeoides Desrousseaux and pertains here. (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. Pterocaulon |
Sibling taxa | ||
Synonyms | Jussiaeahexapetala hooker, J. repens var. major, L. grandiflora subsp. hexapetala, L. grandiflora var. hexapetala, L. uruguayensis var. major | Diplandra decurrens, D. montana, Jussiaea alata, J. bertonii, J. decurrens, J. palustris, J. pterophora, J. tenuifolia |
Name authority | (Hooker & Arnott) Zardini, H. Y. Gu & P. H. Raven: Syst. Bot. 16: 243. (1991) | Walter: Fl. Carol., 89. (1788) |
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