Flora of North America species comparison

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Alternanthera philoxeroides

Alternanthera paronychioides

alligator weed, pig weed

smooth joyweed
Habit Herbs, perennial, aquatic to semiterrestrial, stoloniferous, to 50 dm. Herbs, perennial, 1–8 dm.
Stems

prostrate, forming mats, often fistulose, glabrous.

prostrate, villous, glabrate.
Leaves

sessile;

blade narrowly elliptic, elliptic, or oblanceolate, 3.5–7.1 × 0.5–2 cm, herbaceous, apex acute to obtuse, glabrous.

sessile;

blade elliptic, ovate-rhombic, or oval, 0.6–2.5 × 0.3–1.1 cm, apex acute or obtuse, villous, soon glabrate.
Inflorescences

terminal and axillary, pedunculate;

heads white, globose, 1.4–1.7 cm diam.;

bracts not keeled, less than 1/2 as long as tepals.

axillary, sessile;

heads white, globose, 0.5–1 cm diam.;

bracts less than 1/2 as long as tepals.
Flowers

tepals monomorphic, white, lanceolate or oblong, 6 mm, apex acute, glabrous;

stamens 5;

pseudostaminodes ligulate.

tepals monomorphic, white, lanceolate, 3–5 mm, apex acuminate, without rigid, spinose tips, hairs not barbed;

stamens 5;

anthers 3–5, globose;

pseudostaminodes ligulate, shorter than filaments, margins entire or dentate.
Seeds

not seen.

lenticular, 1.2–1.5 mm.
Utricles

not seen.

included within tepals, stramineous, orbiculate to rounded-obovate, 2–2.3 mm, apex truncate.

Alternanthera philoxeroides

Alternanthera paronychioides
Phenology Flowering early spring–summer. Flowering spring–late fall, year-round in far south.
Habitat Ponds, ditches, streams, bayous Ballast ground, swamps, sandy places, limestone near salt water
Elevation 0-200 m (0-700 ft) 0-10 m (0-0 ft)
Distribution
from FNA
AL; AR; CA; FL; GA; IL; KY; LA; MS; NC; SC; TN; TX; VA; West Indies; native to South America [Introduced in North America]
[WildflowerSearch map]
[BONAP county map]
from USDA
Mexico; Central America; South America; West Indies; Asia; Africa; Pacific Islands [Introduced, Ala., Del., Fla., Ga., La., Miss., N.J., N.C., Pa., S.C., Tenn., Tex.]
[BONAP county map]
Discussion

Alternanthera philoxerioides is said to reproduce only vegetatively in North America. I have seen no fruit or seed.

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

Plants identified as Alternanthera paronychioides var. amazonica Huber have been collected on salt flats in central Louisiana. The specimens I have seen are not sufficiently distinct to warrant varietal recognition.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 4, p. 448. FNA vol. 4, p. 450.
Parent taxa Amaranthaceae > Alternanthera Amaranthaceae > Alternanthera
Sibling taxa
A. brasiliana, A. caracasana, A. ficoidea, A. flavescens, A. maritima, A. paronychioides, A. pungens, A. sessilis
A. brasiliana, A. caracasana, A. ficoidea, A. flavescens, A. maritima, A. philoxeroides, A. pungens, A. sessilis
Synonyms Bucholzia philoxeroides, Achyranthes philoxeroides Illecebrum ficoideum
Name authority (Martius) Grisebach: Abh. Königl. Ges. Wiss. Göttingen 24: 36. (1879) A. St.-Hilaire: Voy. Distr. Diam. 2: 439. (1833)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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