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bushy seedbox, ludwigie à feuilles alternes, rattlebox, seedbox, square-pod water-primrose

Roots

fusiform, fascicled, thickened, epidermis splitting or peeling near base.

Stems

subterete or somewhat angled, with narrow raised lines or wings decurrent from leaf axils, 40–150 cm, well branched in distal 1/2, glabrous or sparsely to densely strigillose.

Leaves

stipules narrowly deltate, 0.05–0.2 × 0.05–0.1 mm;

petiole 0.1–0.3(–0.7) cm;

blade lanceolate-elliptic, (0.6–)2–12 × (0.3–)1–1.5(–2.5) cm, base attenuate, margins entire, apex acute, surfaces strigillose throughout or glabrate with strigillose veins;

bracts often reduced and more linear.

Inflorescences

leafy racemes, flowers solitary in leaf axils;

bracteoles linear-lanceolate, 1–2.5 mm, margins entire, apex acute or subacuminate, glabrous or with scattered hairs, attached near base of ovary.

Flowers

sepals narrowly ovate-deltate, (6–)6.5–9.5 × 4–6.5 mm, margins entire, apex acute to obtuse, surfaces strigillose, sometimes mixed with villous hairs, or glabrate;

petals cordate, 10–14 ×8–12 mm, base attenuate, apex emarginate;

filaments opaque white, awl-shaped, 1–3 mm, anthers 1–1.7 × 0.6–0.8 mm;

ovary subcuboid to globose, 2.5–4 ×2.5–3.5 mm;

nectary disc slightly elevated on ovary apex, 0.8–1.5 mm diam., 4-lobed, ringed with soft, curly hairs or glabrous;

style 1.5–2.4 mm, glabrous, stigma light yellow, capitate to hemispherical, 1–1.3 × 1.4–2 mm, shallowly 4-lobed, not or scarcely exserted beyond anthers.

Capsules

subcuboid to squarish globose, 4–6(–7) × 4–6 mm, 4-angled and 4-winged, wings 0.3–1.5 mm wide, pedicel 2–7 mm.

Seeds

light brown, oblong to reniform, 0.5–0.8 × 0.2–0.4 mm, surface cells elongate transversely to seed length.

2n

= 16.

Ludwigia alternifolia

Phenology Flowering summer–early fall.
Habitat Swamps, damp, peaty places, roadside ditches, margins of cultivated fields.
Elevation 0–1800 m. (0–5900 ft.)
Distribution
from FNA
AL; AR; CO; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MO; MS; NC; NE; NH; NJ; NY; OH; OK; PA; RI; SC; TN; TX; VA; VT; WI; WV; ON; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

Ludwigia alternifolia is widespread and common in the eastern half of the flora area, as far west as Ontario in Canada, eastern Colorado, and Texas.

Ludwigia macrocarpa Michaux 1803 is a superfluous, illegitimate name for L. alternifolia. Rhexia linearifolia Poiret was originally described as a species of Melastomataceae, but the description is superficially similar to Ludwigia and has often been included in synonymy with L. alternifolia. The type of R. linearifolia has not been located or studied.

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

Source FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Ludwigia
Sibling taxa
L. alata, 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, L. virgata
Synonyms Isnardia alternifolia, I. alternifolia var. salicifolia, I. alternifolia var. uniflora, I. aurantiaca, L. alternifolia var. linearifolia, L. alternifolia var. pubescens, L. angustifolia var. ramosissima, L. aurantiaca, L. ramosissima, L. salicifolia, L. uniflora
Name authority Linnaeus: Sp. Pl. 1: 118. (1753)
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