Contains 25 accepted taxa overall.

Characteristics
Ludwigia L.
PRIMROSEWILLOW
Classification
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MYRTALES
Ludwigia
Citation
LUDWIGIA Linnaeus, Sp. Pl. 188. 1753 (Ludvigia); corr. Linnaeus, Gen. Pl., ed. 5. 55. 1754.
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TYPE: Ludwigia alternifolia Linnaeus Lectotypified by Britton & A. Brown, Ill. Fl. N. U.S., ed. 2. 2: 586. 1913.
Species
Scientific Name Common Name Herbarium Specimens Status Photos
Ludwigia alata Winged Seedbox
Ludwigia alternifolia Alternate-leaf Seedbox
Ludwigia arcuata Piedmont Primrose-willow
Ludwigia bonariensis Carolina primrose-willow
Ludwigia brevipes Long Beach Seedbox, Coastal Plain Water-purslane
Ludwigia decurrens Wingstem Water-primrose
Ludwigia glandulosa Small-flowered Seedbox
Ludwigia grandiflora Showy Water-primrose
Ludwigia hexapetala Common Water-primrose
Ludwigia hirtella Rafinesque's Seedbox
Ludwigia lanceolata Lanceleaf Seedbox
Ludwigia leptocarpa Water-willow
Ludwigia linifolia Flaxleaf Seedbox
Ludwigia maritima Harper's Seedbox
Ludwigia microcarpa Small-fruited Seedbox
Ludwigia octovalvis Mexican primrose-willow
Ludwigia palustris Common Water-purslane
Ludwigia peploides var. glabrescens Floating Primrose-willow
Ludwigia pilosa Hairy Seedbox
Ludwigia ravenii Raven's Seedbox
Ludwigia repens Creeping Seedbox
Ludwigia spathulata Southern Water-purslane
Ludwigia sphaerocarpa Globe-fruited Seedbox
Ludwigia suffruticosa Shrubby Seedbox
Ludwigia virgata Savanna Seedbox
Identification Key
1.  Leaves opposite
1.  Leaves alternate
2
2.  Stamens 4-5 per flower, as many as the sepals
2.  Stamens 8-10 per flower, twice the number of sepals
3
3.  Sepals 5(-7)
3.  Sepals 4
1.  (Key A) Pedicels 6-45 mm long
2
1.  Pedicels 0-2(-5) mm long
3
2.  Pedicel mostly subequal to shorter than the subtending leaf; petals 4-5 mm long
2.  Pedicel usually much longer than the subtending leaf; petals 7-11 mm long
3.  Plant densely strigulose
3.  Plant glabrate
4
4.  Sepals 1-2.1 mm long; petals absent; anthers 0.2-0.4 mm long, the pollen shed as monads; faces of fruit with a longitudinal band or obscure line running down from the sepal midrib, the appearing dissimilar from the corners
4.  Sepals 1.8-5 mm long; petals present but often quickly deciduous; anthers 0.4-0.9 mm long, the pollen sheds as tetrads; fruit faces and corners similar in appearance
1.  (Key B) Fruit much longer than wide
2
1.  Fruit about as long as wide
4
2.  Leaf blades elliptic, lanceolate, ovate, to oblanceolate, larger ones 4-12 mm wide; petals absent; fruit with a groove descending from the middle of the calyx lobe
2.  Leaf blades linear to linear-oblanceolate, larger ones 1-4 mm wide; petals present; fruit without a groove
3
3.  Calyx lobes 2-3 mm long, much shorter than the quadrangular fruit
3.  Calyx lobes 5-6 mm long, ca. 0.6-1 times longer than the subcylindric fruit
4.  Pedicel apparent, 3-20 mm long
5
4.  Pedicel scarcely evident, 0-2 mm long
8
5.  Leaf blade base cuneate-attenuate
5.  Leaf blade base rounded to obtuse
6
6.  Proximal leaf blades glabrous; style 7-10 mm long, longer than the sepals
6.  Proximal leaf blades pubescent; styles to 3 mm long, shorter than the sepals
7
7.  Plant hirsute
7.  Plant pubescent to puberulent
8.  Flowers several in a densely congested in a terminal spike with bract-like leaves
8.  Flowers mostly separated along a leafy racemes or interrupted spike, or few in a congested, bracteate terminal spike
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9.  Plant hirtellous
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9.  Plant glabrous to strigillose
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10.  Sepals whitish along the upper surface and often tinged pink along the midvein and edge, the apex long-acuminate to subcuspidate and reflexed; anther 0.6-1.3 mm long, filament 0.7-1.1 mm long; style glabrous, 0.25-0.5 mm long; nectary disc hirtellous between the lobes
10.  Sepals greenish on the upper surface, the apex acuminate and ascending; anther ca. 0.3 mm long, filament 1.5-2.5 mm long; style hirtellous, 1-2 mm long; nectary disc glabrous
11.  Capsule quadrangular or winged
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11.  Capsule not angular, not winged
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12.  Stem usually ridged or winged; sepals whitish and subequal to the fruit
12.  Stems usually smooth to obscurely ridged; sepals greenish, ca. ½ as long as the fruit
13.  Sepals 1-2 mm long; fruit 1-1.5 mm long; seeds reddish brown
13.  Sepals 2-4 mm long; fruit 1.5-7 mm long; seeds tan to yellowish
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14.  Leaf blades obovate, spatulate, to oblanceolate
14.  Leaf blades linear-lanceolate to oblong-elliptic
1.  (Key C) Stems prostrate to decumbent, rooting
2
1.  Stems erect to ascending, not rooting at least distally
3
2.  Bracteoles below hypanthium lanceolate; hypanthium subequal to shorter than the sepals
2.  Bracteoles below hypanthium deltoid to ovate; hypanthium longer than the sepals
3.  Fruit cylindric, 3-5 cm long (much longer than the pedicel), 2-4 mm wide
3.  Fruit obconic, quadrangular, 1-3 cm long (subequal to the pedicel), 5-10 mm wide
1.  (Key D) Stem conspicuously 4-winged
2
1.  Stem without wings or slightly ridged on the angles
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2.  Leaf blades lanceolate, ovate-lanceolate, to elliptic
2.  Leaf blades linear-lanceolate
3.  Stems hirsute to villous
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3.  Stems glabrate
5
4.  Fruit more than twice as long as the sepals, with a distinct ridge descending from the sepal midvein
4.  Fruit subequal to slightly longer than the sepals, without a ridge continuous with the sepal midvein
5.  Calyx lobes 3-4 mm long; petals 4-5 mm long
5.  Calyx lobes (5-)10-15 mm long; petals (10-)15-30 mm long
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6.  Pedicel shorter than the hypanthium; hypanthium subequal to slightly longer than the sepals
6.  Pedicel longer than the hypanthium; hypanthium more than twice as long as the sepals
Genus Synonyms
Synonym Full Citation Basionym Type
No synonyms found.