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globefruit primrose-willow, round-pod water-primrose

Habit Herbs often with prominent aerenchyma when base submerged, forming stolons 20–90 cm, 2–3.5 mm thick, floating, sometimes branched.
Stems

erect, slightly ridged, well branched, (40–)60–110 cm, densely strigillose or glabrous.

Leaves

alternate;

stipules lanceolate-deltate, 0.1–0.4 × 0.1–0.2 mm;

stolons: petiole ± winged, 0.1–0.3 cm, blade narrowly elliptic to oblanceolate or spatulate, 0.9–3 × 0.4–0.8(–1.3) cm, base attenuate, margins subentire with hydathodal glands, apex acute or obtuse;

stems: petiole 0.1–0.4(–1) cm, blade narrowly elliptic or lanceolate to sublinear, on main stem (2.6–)6–10 × 0.5–1.1(–1.6) cm, on branches 2–5(–6) × 0.3–0.5(–0.6) cm, base attenuate or narrowly cuneate, margins entire with hydathodal glands mainly on primary cauline leaves, apex acute to very narrowly acute, surfaces glabrous or densely strigillose;

bracts not much reduced.

Inflorescences

open, leafy racemes, more congested on branches, flowers solitary in leaf axils;

bracteoles attached in subopposite pairs near base of ovary, usually linear to very narrowly lanceolate, rarely lanceolate, 0.5–1.5 × 0.1–0.3 mm, apex acuminate.

Flowers

sepals ascending, yellow or cream adaxially, ovate-deltate, 2–3.5(–4) × 1.6–3(–3.3) mm, margins entire, apex acuminate, surfaces glabrous or densely strigillose;

petals 0;

filaments yellow, 1–1.7 mm, slightly dilated toward base, anthers 0.5–0.8 × 0.4–0.7 mm;

pollen shed in tetrads;

ovary broadly obovoid or cup-shaped, 1.5–3.5 × 2–3 mm;

nectary disc elevated 0.4–0.6 mm on ovary apex, bright yellow, 1.5–3 mm diam., 4-lobed, glabrous or short-hirtellous between lobes;

style yellow, 0.6–1(–1.3) mm, glabrous or strigillose proximally, stigma yellow, capitate to subglobose, 0.3–0.5 × 0.4–0.7 mm, not exserted beyond anthers.

Capsules

sometimes tinged pink, subglobose, subterete, 2–4(–4.5) × 2–4 mm, hard-walled, irregularly dehiscent, pedicel 0.5–1.2(–2.3) mm.

Seeds

brown to light brown, elliptic, 0.4–0.7 × 0.3–0.4 mm, surface cells transversely elongate to seed length, sometimes oblique.

2n

= 32.

Ludwigia sphaerocarpa

Phenology Flowering Jun–Sep.
Habitat Drainage ditches, shores of slow-moving streams or ponds, marshes, swales, swamp forests, edges of limestone sinks, peaty bogs in pastures, interdunal marshes.
Elevation 0–300 m. (0–1000 ft.)
Distribution
from FNA
AL; CT; DE; FL; GA; IL; IN; LA; MA; MD; MI; MS; NC; NJ; NY; PA; RI; SC; TN; TX; VA
[WildflowerSearch map]
[BONAP county map]
Discussion

Ludwigia sphaerocarpa has its primary distribution along the Atlantic coastal plain, from Massachusetts to north-central Florida, and west along the Gulf coastal plain sporadically to southeastern Texas. Disjunct populations occur in south-central Tennessee, extreme southwestern Indiana, along Lake Michigan in northeastern Illinois and northwestern Indiana, and in west-central New York. In Michigan, L. sphaerocarpa is known from Allegan and Berrien counties, as reported by Reznicek and Voss in the Michigan Flora (https://michiganflora.net/species.aspx?id=1757).

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

Source FNA vol. 10.
Parent taxa 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. 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. suffruticosa, L. virgata
Synonyms Isnardia sphaerocarpa, L. sphaerocarpa var. deamii, L. sphaerocarpa var. jungens, L. sphaerocarpa var. macrocarpa
Name authority Elliott: Sketch Bot. S. Carolina 1: 213. (1817)
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