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Piedmont primrose-willow

creeping seedbox, cylindricfruit primrose-willow

Habit Herbs usually creeping and rooting at nodes, forming mats. Herbs slender, forming stolons 5–20 cm, 0.4–0.8 mm thick.
Stems

prostrate or decumbent and ascending at tips, slightly ridged, often well branched, 5–70 cm, glabrate to sparsely strigillose, denser on distal parts.

erect, slightly ridged, usually well branched, 10–80(–100) cm, glabrate or often with strigillose raised lines decurrent from leaf axils.

Leaves

opposite;

stipules narrowly deltate or ovate, 0.05–0.15 × 0.05–0.1 mm; submerged stems: petiole 0–0.2 cm, blade narrowly linear, 1.9–4 ×0.1–0.25 cm;

emergent stems: petiole 0–0.2 cm, blade narrowly elliptic or narrowly oblanceolate-elliptic to linear, 0.6–1.8 × 0.2–0.5 cm, base narrowly cuneate, margins entire, apex acute, surfaces glabrous or sparingly strigillose on margins and abaxial midveins;

bracts reduced.

alternate;

stipules ovate-triangular, 0.15–0.35 × 0.05–0.25 mm, succulent;

stolons: petiole attenuate, 0.3–1 cm, blade narrowly elliptic, 1.5–3.5(–5.5) × 0.5–1.3(–2) cm;

main stem: petiole 0–1.5 cm, blade usually narrowly elliptic to elliptic, sometimes linear, 3–12 × 0.3–2.1 cm, base attenuate, margins subentire with hydathodal glands often visible, apex acute to very narrowly acute, surfaces densely papillose-strigillose, abaxial veins glabrous or sparingly, minutely strigillose;

leaves on side branches usually reduced, 0.8–4.5 ×0.2–1 cm;

bracts much reduced.

Inflorescences

in racemes or spikes, well-formed on ascending stems, not on prostrate stems;

bracteoles attached at base of ovary or 1.5–8 mm proximally on pedicels, sublinear to very narrowly elliptic, 1.4–5 × 0.2–0.8 mm, apex acute, surfaces minutely strigillose.

open, leafy racemes or spikes, flowers solitary in axils, often congested, especially on branches;

bracteoles attached on pedicel at base of ovary or to 2 mm distal to base, narrowly lanceolate to sublinear, 0.4–1 × 0.1–0.4 mm, apex acuminate, surfaces glabrate.

Flowers

sepals reflexed or spreading, green, lanceolate-deltate, 5.2–10 ×1.5–2.7 mm, with 3 prominent parallel veins, margins entire and minutely strigillose, apex acute or elongate-acuminate, surfaces minutely strigillose abaxially;

petals rarely caducous, elliptic-obovate to spatulate-obovate, 7–11 × 4.5–8 mm, base attenuate, apex rounded;

filaments initially spreading, becoming erect, yellow, 2.5–4.5 mm, anthers 1.3–2 × 0.7–1.1 mm;

pollen shed in tight tetrads;

ovary cylindric to funnelform, 4–5.5 × 1.5–2.8 mm;

nectary disc elevated 0.6–1 mm on ovary apex, 1.5–2.6 mm diam., bright yellow, with 4 distinct domed lobes, minutely strigillose between lobes or glabrous;

style yellow, 2.3–4(–4.8) mm, glabrous, stigma yellow, broadly capitate, 0.3–0.6 × 0.6–1.8 mm, as long as or exserted beyond anthers.

sepals ascending, light green, ovate-deltate, 1.1–2.3 × 1–1.8 mm, margins entire, fringed with minute, strigillose hairs, apex short-acuminate or acute, surfaces glabrous;

petals 0;

filaments nearly translucent, 0.6–1.1 mm, anthers 0.3–0.5 × 0.3–0.6 mm;

pollen shed in tetrads;

ovary subcylindric, 2–5 × 0.8–1.9 mm;

nectary disc elevated 0.3–0.4 mm on ovary apex, light green, 0.6–1.8 mm diam., 4-lobed, glabrous or minutely papillose;

style pale green, 0.3–0.8 mm, glabrous, stigma broadly clavate to subglobose, 0.2–0.5 × 0.2–0.5 mm, not exserted beyond anthers.

Capsules

clavate, subterete, sometimes slightly curved, 5.5–10 × 2.3–4 mm, hard-walled, irregularly dehiscent, pedicel (12–)17–45 mm.

subcylindric, subterete to obscurely 4-angled with 4 shallow grooves, 2–8(–9) × 1.3–2(–3) mm, hard-walled, irregularly dehiscent, pedicel 0–0.3(–0.5) mm.

Seeds

light to dark brown, elliptic-oblong, 0.5–0.7 × 0.3–0.4 mm, surface cells transversely elongate.

light brown, kidney-shaped with slightly pointed ends, 0.5–0.8 × 0.3–0.4 mm, surface cells columnar, elongate either parallel or transversely to seed length.

2n

= 32.

= 32.

Ludwigia arcuata

Ludwigia glandulosa

Phenology Flowering Mar–Aug.
Habitat Roadside ditches, edges of lakes or ponds, swampy prairies, springs, mucky or sandy beach strands.
Elevation 0–150 m. (0–500 ft.)
Distribution
from FNA
AL; FL; GA; SC
[BONAP county map]
from USDA
c United States; e United States
[WildflowerSearch map]
[BONAP county map]
Discussion

Ludwigia arcuata is common in its range, but geographically restricted to central and western parts of peninsular Florida and adjacent Georgia, extending to southern South Carolina. Disjunct populations have been collected in Bibb County in central Georgia and Mobile County, Alabama.

The tetraploid Ludwigia arcuata has the largest flowers in sect. Isnardia and is the most consistently outcrossing species; C. I. Peng (1989) reported abundant insect visitors on this species. It is morphologically most similar to the hexaploid L. brevipes, with which it shares two genomes (Peng).

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

Subspecies 2 (2 in the flora).

Ludwigia glandulosa consists of two subspecies: subsp. glandulosa is very common and widespread throughout the Atlantic and Gulf coastal plains and the Mississippi Embayment, westward to eastern Texas and southeastern Oklahoma; subsp. brachycarpa grows only in the western portion of the range of subsp. glandulosa, extending farther west in Texas and Oklahoma. The two taxa grow in similar habitats, but subsp. glandulosa prefers drier habitats farther south and west. The general distinctiveness of these subspecies is probably maintained by their modal autogamy; vegetative reproduction by means of stolons may likewise play a role in preserving favored genotypes (C. I. Peng 1989).

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

Key
1. Capsules (4–)5–8(–9) mm; cauline leaf blades 3.2–12 × 0.4–2.1 cm; seeds: surface cells elongate parallel to seed length.
subsp. glandulosa
1. Capsules 2–5 mm; cauline leaf blades 3–5(–7) × 0.3–0.5(–1) cm; seeds: surface cells elongate transversely to seed length.
subsp. brachycarpa
Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Isnardia Onagraceae > subfam. Ludwigioideae > Ludwigia > sect. Isnardia
Sibling taxa
L. alata, L. alternifolia, 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
L. alata, L. alternifolia, L. arcuata, L. bonariensis, L. brevipes, L. curtissii, L. decurrens, L. erecta, 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
L. glandulosa subsp. brachycarpa, L. glandulosa subsp. glandulosa
Synonyms Isnardia arcuata, I. pedunculosa, L. pedunculosa, Ludwigiantha arcuata
Name authority Walter: Fl. Carol., 89. (1788) Walter: Fl. Carol., 88. (1788)
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