Alligator-weed

Alternanthera philoxeroides

In the Carolinas and Georgia, found in floating in mats on the surface of the waters of blackwater rivers, sloughs, ditches, ponds, and in very moist soil of ditches and shores. Weakley, Flora of the Southeastern United States (2025), Carolinas & Georgia edition What its natural habitat tells you

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Severe harm

Not native to Louisiana. How scores work Is it native here?

Profile 82%

Height: About 2.4 inches
Light: Full sun, Partial shade
Soil moisture: Moist to standing water

See native alternatives

Alternanthera philoxeroides — flower photograph — National Plant Data Center, Baton Rouge, LA 70874-4490 USA. · Public domain · Original photograph

Do not plant. Listed invasive in Louisiana.

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At a glance

Life cycle: Perennial
Bloom: March to October
Fruiting season: Spring to summer

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Not yet recorded · Spread · Leaves

Recorded in 58 Louisiana parishes.

Natural habitats

Places it grows wild. Not a planting requirement. Each habitat page lists the plants and wildlife also found there.

1 of 3

Streams, rivers and their banks

Flowing water and its banks, bars and rocky shoals.

Roadsides, fields and disturbed ground

Ground opened by people: roadsides, old fields, pastures, fencerows and lots.

Ponds, lakes and their shores

Still water and its edges: ponds, lakes, millponds and reservoirs.

All habitats

Ecological relationships

Who uses this plant?

What these records mean

8CaterpillarsGenus host records with ranges including LA

Genus host records with ranges including LA · Alternanthera

Herpetogramma bipunctalisSouthern Beet Webworm, Two-Spotted Herpetogramma
Hymenia perspectalisSpotted Beet Webworm
Macrorrhinia endonepheleReddish Macrorrhinia/Alligatorweed Stem Borer Moth
Spodoptera frugiperdaFall Armyworm Moth
Spodoptera ornithogalliYellow-Striped Armyworm Moth, Cotton Cutworm
Spoladea recurvalisHawaiian Beet Webworm
Staphylus hayhurstiiHayhurst's Scallopwing, Scalloped Sooty Wing, Scalloped Sootywing
Endothenia microptera

Shropshire & Tallamy 2025, Lepidoptera of North America north of Mexico, ZooKeys 1261 (ODbL)

—BeesSoutheastern regional records

—Specialist beesPollen specialists

—BirdsRecorded genus food-resource interactions; not a state feeding claim

Growing and identification

Plant details

Family: Amaranthaceae
Hardiness: Zones 7a–10b
Flower color: White
Growth rate: Rapid
Growth habit: Spreads by runners
Foliage color: Green
Fruit begins: Spring
Fruit ends: Summer

Safety has not been reviewed for this plant; check toxicity and thorns before planting.

Growing sources and scope

Bloom · “March to October” · Weakley, Flora of the Southeastern United States (2025), Carolinas & Georgia edition (ranked first; USDA PLANTS differs) · Carolinas and Georgia
Flower color · “White” · NC Extension Plant Toolbox
Foliage color · “Green” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Fruit begins · “Spring” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Fruit ends · “Summer” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Growth habit · “Spreads by runners” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Growth rate · “Rapid” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Hardiness · “Zones 7a–10b” · NC Extension Plant Toolbox
Height · “About 2.4 inches” · USDA PLANTS · Nationwide species characteristics; local growing conditions may vary
Life cycle · “Perennial” · NC Extension Plant Toolbox
Light · “Full sun (6 or more hours of direct sunlight a day); Partial shade (direct sunlight only part of the day, 2-6 hours)” · NC Extension Plant Toolbox
primary_flower_color · “white” · USDA PLANTS
Soil · “Frequent standing water; Moist; Occasionally wet” · NC Extension Plant Toolbox

Also known as

Alligator Weed

Conservation status

Louisiana rank	SNA
Global rank	GNR
LA status	Not verified
Federal status	Not verified

Conservation source Global and federal source