Alligator-weed
Alternanthera philoxeroides
Last reviewed: August 2026
Toxicity unknown
Alligator-weed (Alternanthera philoxeroides) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.
The USDA PLANTS Database (opens in new tab) does not flag Alligator-weed as toxic to livestock.
Light
full sun
Water
high
Size
12"–36" H × 24"–120" W
Bloom
Jun, Jul, Aug
Native alternatives to Alligator-weed
Alligator-weed is not native to the United States. These natives fill a similar role in a planting, matched on bloom season, bloom color and mature size.
Before you buy
Your city may pay you to plant this
Cities and water utilities offer rebates for replacing lawn with native and water-wise plants. We track 452 programs across 44 states, each with a link to the provider and the date we last checked it.
Find rebates in your areaAlligator-weed is an aggressive aquatic and semi-aquatic vine that spreads rapidly through waterways and wet areas. This invasive species forms dense mats that can quickly overtake native vegetation and is extremely difficult to control once established.
In an HOA neighborhood
Alligator-weed takes more care to keep looking intentional in a front yard. Maintenance level: high. Consider it for backyard or mid-zone beds rather than the street edge.
- Classified as invasive species
- Spreads aggressively and uncontrollably
- May violate local noxious weed ordinances
Wildlife value
While it may provide some habitat for aquatic insects, this invasive plant displaces native species that offer much better wildlife value. Its aggressive nature actually reduces overall biodiversity in affected areas.
Common questions
- How much sun does Alligator-weed need?
- Alligator-weed grows best in full sun conditions.
- When does Alligator-weed bloom?
- Alligator-weed blooms in June, July, and August.
- Is Alligator-weed toxic to livestock?
- The USDA PLANTS Database does not flag Alligator-weed as toxic to livestock.
- Is Alligator-weed HOA-friendly?
- Alligator-weed takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.
Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
If something looks wrong
Common plant problems, and what to check first
These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.
- It is dying right after planting
- Leaves turning yellow
- Wilting even though I watered it
- Brown crispy leaf tips
- Bugs on the plant
Ready to grow Alligator-weed? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.
Planning a bed around it? Start a free plan with this plant
Not sure where to start? Take the 2-minute yard quiz