Alligator-weed
Alternanthera philoxeroides
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. FloraQuest, phone app (app page) What its natural habitat tells you
-85
Severe harm
Not native to Virginia. 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
Do not plant. Listed invasive in Virginia.
Plant this instead
Choose your county to list local plants first.
- Manyflower Marsh-pennywortHydrocotyle umbellata
Similar growth form, evergreen or deciduous, bloom season
No recorded swaps for this county. Try the garden finder.
At a glance
- Life cycle
- Perennial
- Bloom
- March to October
- Fruiting season
- Spring to summer
JFMAMJJASOND
Not yet recorded · Spread · Leaves
Recorded in 13 Virginia counties.
Natural habitats
Places it grows wild. Not a planting requirement.
1 of 2
Streams, rivers and their banks
Habitats
Streams, rivers and their banks; roadsides, fields and disturbed ground; ponds, lakes and their shores.
Each habitat page lists the plants and wildlife also found there. All habitats
Ecological relationships
Who uses this plant?
6CaterpillarsGenus host records with ranges including VA
Genus host records with ranges including VA · Alternanthera
- Herpetogramma bipunctalisSouthern Beet Webworm, Two-Spotted Herpetogramma
- Hymenia perspectalisSpotted Beet Webworm
- Spodoptera frugiperdaFall Armyworm Moth
- Spodoptera ornithogalliYellow-Striped Armyworm Moth, Cotton Cutworm
- Spoladea recurvalisHawaiian Beet Webworm
- Staphylus hayhurstiiHayhurst's Scallopwing, Scalloped Sooty Wing, Scalloped Sootywing
—BeesSoutheastern regional records
—Specialist beesPollen specialists
—BirdsRecorded genus food-resource interactions; not a state feeding claimGrowing 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” · FloraQuest: Carolinas, Georgia (Southeastern Flora Team), phone app (app page) (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
| Virginia rank | SNA |
|---|---|
| Global rank | GNR |
| VA status | Not verified |
| Federal status | Not verified |
Sources
- Virginia DCR invasive plant list
- Digital Atlas of the Virginia Flora
- USDA PLANTS
- FloraQuest: Carolinas, Georgia (Weakley), phone app (app page)
- FloraQuest: Northern Tier (Weakley), phone app (app page)
- NatureServe Explorer
- Shropshire & Tallamy 2025, Lepidoptera of North America north of Mexico, ZooKeys 1261 (ODbL)
- Noori, Seltmann & Orr 2026, A curated and integrated dataset for exploring global bee-plant interactions (GloBI), Zenodo, CC BY 4.0
- Smith, Bachelder, Russell, Morales, Mosher & Seltmann 2024, Bee-Specialization-Modeling v0.6.1 (specialist host table compiled from J. Fowler's pollen specialist bee lists), Zenodo, CC BY 4.0
- Hurlbert, Olsen, Sawyer & Winner 2021, Avian Diet Database, Scientific Data 8: 260 (CC0)
- Narango, Tallamy & Shropshire 2020, Few keystone plant genera support the majority of Lepidoptera species, Nature Communications