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Carolina primrose-willow

Habit Herbs, from woody rootstock. Herbs, perennial, or shrubs.Stems erect or spreading, terete, subterete, or ridged.

erect, subterete, 20–120 cm, branched, glabrate proximally, or strigillose, especially in distal parts, with raised strigillose lines decurrent from leaf axils mid stem.


stipules narrowly deltate, 0.3–0.5 × 0.1–0.2 mm;

petiole winged, 0.1–0.7 cm;

blade narrowly to broadly lanceolate, 4–15 × 0.3–1(–3) cm, base tapered, margins subentire to inconspicuously glandular-serrulate, apex acute to acuminate, surfaces finely strigillose, especially on abaxial veins, sometimes glabrate;

bracts narrower, reduced in size.



open, leafy racemes, flowers solitary in axils;

bracteoles lanceolate-linear or setaceous, 2–6 × 0.3–0.8 mm, attached on pedicel just proximal to base of ovary.


sepals ovate-deltate, 10–20 × 7–12 mm, abruptly acuminate or acute, inconspicuously 5–7-nerved, surfaces strigillose;

petals deep golden yellow, broadly obovate, 20–35 × 10–30 mm, apex shallowly emarginate, claw 1.5–3 mm;

stamens 8 in 2 unequal series, filaments flattened and dilated near base, epipetalous set 3.4–4.5 mm, episepalous set 4.5–5.5 mm, anthers oblong, 4–5 mm;

pollen shed in polyads;

ovary subcylindric, slightly 4-angled, 8–12(–20) mm;

nectary disc slightly elevated on ovary apex, 2–3 mm diam., 4-lobed, ringed by short hairs;

style 3–3.5 mm, stigma clavate-capitate, 2.5–3 × 2–2.5 mm, often exserted beyond anthers.


petals present, yellow;

stamens 2 times as many as sepals;

pollen shed in tetrads or polyads.


clavate-cylindric, subterete to obtusely 4-angled, 20–35 × 3.5–5 mm, thin walls, irregularly dehiscent, tapering to pedicel 10–40 mm.

cylindric to clavate-cylindric, ± angled to subterete, with thin walls, irregularly dehiscent.


in several indistinct rows per locule, yellow-brown, oblong (appearing round), 0.5 mm, shiny, raphe 2/3 as wide as body.

in several rows per locule, free, raphe enlarged, nearly equal to seed.


= 16.

= 16, 32, 48.

Ludwigia bonariensis

Ludwigia sect. Macrocarpon

Phenology Flowering summer.
Habitat Wet places, mainly along coastal areas, especially ditches, banks near brackish water.
Elevation 0–200[–2600] m. (0–700[–8500] ft.)
from FNA
AL; FL; MS; NC; SC; TX; Mexico (Chihuahua, Durango, Puebla, Quintana Roo, Tabasco, Tamaulipas, Veracruz); South America (Argentina, Bolivia, Brazil, Paraguay, Uruguay)
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se United States; Mexico; Central America; South America; s United States; West Indies; Eurasia; Africa; Indian Ocean Islands; Pacific Islands; Australasia

Species 4 (2 in the flora).

Section Macrocarpon consists of four species, all of which occur in Argentina, Brazil, and Paraguay. Ludwigia bonariensis also occurs as a disjunct in Mexico and the southern United States; L. octovalvis is found worldwide in subtropical and tropical areas and is widely distributed in the southern United States. Section Macrocarpon, which is supported as monophyletic by molecular data (Liu S. H. et al. 2017), differs from sect. Myrtocarpus by having strictly 4-merous (versus 4+-merous) flowers, cylindric (versus obconic) capsules, and distinctive seeds with an enlarged raphe.

Ludwigia bonariensis and L. lagunae are diploid (n = 8) and self-incompatible; L. neograndiflora is tetraploid (n = 16; Liu S. H. et al. 2017), but compatibility is unknown. In contrast, most populations of the multiploid L. octovalvis are polyploid, with some reports of diploids in the New World (P. H. Raven and W. Tai 1979), and self-compatible. Ludwigia octovalvis is extremely variable in morphology and ploidy level, and the entire section is in need of taxonomic revision.

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

Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Macrocarpon Onagraceae > subfam. Ludwigioideae > Ludwigia
Sibling taxa
L. alata, L. alternifolia, L. arcuata, 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
Subordinate taxa
Synonyms Jussiaea bonariensis, J. neglecta, J. suffruticosa var. bonariensis Jussiaea section macrocarpon
Name authority (Micheli) H. Hara: J. Jap. Bot. 28: 291. (1953) (Micheli) H. Hara: J. Jap. Bot. 28: 291. (1953)
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