Ludwigia grandiflora
Ludwigia sect. Jussiaea
large-flower primrose-willow, Uruguayan primrose-willow
erect or ascending to creeping or floating, terete or sometimes angled distally, 20–300(–450) cm, usually densely branched, sometimes simple, glabrous if floating, or densely villous and viscid throughout, or rarely just on inflorescence.
decumbent to erect or ascending, terete, sometimes angled distally.
stipules (rarely in clusters of 3), ovate-deltate, 0.6–2 × 0.6–1.5 mm, fleshy, apex subacute, often mucronate;
petiole 0.1–1.1 cm;
blade usually lanceolate to (narrowly) elliptic or oblanceolate, rarely narrowly obovate, (1.7–)3.1–8(–10.5) × 0.5–2(–2.5) cm, chartaceous, viscid, base cuneate or attenuate, margins entire, apex obtuse or acute, always glandular-mucronate, surfaces densely villous, sometimes less dense adaxially, distal leaves more pubescent than proximal ones;
bracts scarcely reduced.
alternate or fascicled.
on emergent stems sometimes in leafy racemes, flowers solitary in leaf axils;
bracteoles narrowly to broadly obovate, 1–1.2 × 0.7–0.8 mm, succulent, apex acute, oppositely attached at ovary base.
sepals usually deciduous, not persistent on capsule, lanceolate, 6–12(–16) × 2–4 mm, chartaceous, apex acute, surfaces densely villous;
petals yellow, fan-shaped, (12–)16–20(–26) × 11–16(–21) mm, apex rounded, usually emarginate, rarely mucronate;
stamens 10(or 12), in 2 unequal series, yellow, filaments reflexed, shorter ones (2.8–)3.8–5.3 mm, longer ones (3.7–)6–6.5 mm, anthers oblong, 1–2.5 × (0.6–)0.8–1.2 mm;
ovary subcylindric, terete, 6–12 × 1.5–2.5 mm, apex thickened, densely villous;
nectary disc slightly raised on ovary apex, yellow, 1.5–2.5 mm diam., lobed, ringed with villous hairs;
style yellow, 4.7–6.7(–8) mm, glabrous or sparsely pubescent near base, stigma subcapitate-globose, 1–1.3 × 1.6–2.5 mm, usually exserted beyond anthers.
5(or 6)-merous;
petals present, yellow [white];
stamens 2 times as many as sepals, [rarely as many as];
pollen shed as monads.
subcylindric, terete, straight or curved, (11–)14–25 × 3–4 mm, with thick woody walls, irregularly and tardily dehiscent, villous-viscid, pedicel 13–25(–27) mm.
cylindric, subcylindric, or subclavate, terete, subterete, or obscurely angled, often up-curved, with thick, woody walls, irregularly and tardily dehiscent.
embedded in wedge-shaped piece of endocarp, 0.8–1 × 0.8–0.9 mm.
in 1 row per locule, pendulous and firmly embedded in woody, coherent segment of endocarp, raphe inconspicuous.
= 48.
= 16, 32, 48, 80, 96.
Ludwigia grandiflora
Ludwigia sect. Jussiaea
Ludwigia grandiflora occurs in two disjunct areas: the southeastern United States on the coastal plain of southern South Carolina, Georgia, northern Florida, Louisiana, west to central Texas, and recently in southern California (P. C. Hoch and B. J. Grewell 2012) and Oregon; and central South America from south of the Amazon basin of Brazil and Bolivia where it is very scattered, to Uruguay, northeastern Argentina, and Paraguay where it is very frequent. It has been collected three times in Guatemala and twice in Missouri, although it is not clearly established in either region. It usually grows below 200 m elevation, but in Guatemala and in Santa Catarina, Brazil (Smith & , MO), it has been collected as high as Klein 133831200 m elevation. Populations of L. grandiflora in the United States are fairly variable, although not as much as in South American populations.
As noted by Greuter and Burdet, the publication of Jussiaea grandiflora Ruíz & Pavon, which was a synonym of J. peruviana, occurred in 1830, not in 1802 as reported (P. A. Munz 1942; P. H. Raven 1963[1964]). Therefore, J. grandiflora Michaux in 1803 is legitimate, and J. grandiflora Ruíz & Pavon is an illegitimate homonym.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 9 (3 in the flora).
This cosmopolitan polyploid section of nine variable species (11 taxa) includes three diploid species (n = 8), four tetraploids (n = 16), one hexaploid [Ludwigia grandiflora, n = 24; P. H. Raven and W. Tai (1979) reported one anomalous count of n = 48], and one decaploid (L. hexapetala, n = 40; see also G. L. Nesom and J. T. Kartesz 2000). One persistent triploid (2n = 24) hybrid, described as L. ×taiwanensis C. I. Peng [L. adscendens (n = 16) × L. peploides subsp. stipulacea (n = 8); Peng 1990] is widespread in southern China and Taiwan. E. Zardini et al. (1991) reported several other natural hybrids.
Most species of sect. Jussiaea have non-naturalized distributions restricted to the New World. Section Jussiaea differs from most diplostemonous sections by releasing its pollen as monads and having woody, subcylindric capsules with uniseriate, firmly embedded seeds. Most species in sect. Jussiaea are vigorously aquatic, and several (including L. peploides, L. hexapetala, and L. grandiflora) can be invasive weeds in wetlands and wet agricultural areas; the latter two, or all three, species have recently become major invasive species in California, particularly in the Russian and Sacramento river drainages and in the San Diego region, in Arizona (especially Gila and Salt rivers), and in Washington (M. Wood 2006; P. C. Hoch and B. J. Grewell 2012).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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LA Plants
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