Alligator Weed
-
Scientific Name
Alternanthera philoxeroides - Visit ITIS for full scientific classification.
-
DescriptionAlligator Weed flower. Courtesy CDFA IPC Program. © 2005 Regents, University of CaliforniaAlligator Weed plants at shoreline. D.O. Clark. © 2007 Regents, University of California
- Dense, floating mats that are rooted in soil of shallow water.
- Floating form has hollow stems and terrestrial form has solid stems.
- Stems can reach over 3 feet long.
- Leaves are in pairs along stem.
- Leaves are narrow: up to 4 1/3" long and up to 1" wide.
- Flower spikes are fragrant, pearly and up to 3 1/2" long.
-
Habitat
- Shallow, slow moving water or wet (or sometimes dry) soil.
- Tolerates up to 10% salinity.
- Needs warm summer.
- Can tolerate cold winter but not a long freeze.
-
Invasion Pathways and Distribution
- Believed to have been introduced from South America.
- Also occurs in Central America.
- In California it is found in the San Joaquin Valley and in Los Angeles, San Bernardino and Riverside Counties.
- Pieces of mats break off and can infest new areas.
-
Life History
- Rarely produces seed.
- Spreads by stolons (a type of stem) that produce new plants.
-
Impacts
- Dense mats reduce light and displace native species.
- Especially heavy infestations can reduce oxygen and favor mosquitos.
-
References and Useful Links
For references by category and links to other useful AIS sites see our LEARN MORE page.