Spermatophytes (seed plants): Angiosperms (flowering plants): Eudicots: Core Eudicots: Caryophyllales
WEAKLEY'S FLORA OF THE SOUTHEASTERN US (4/24/22):
Alternanthera philoxeroides
FAMILY
Amaranthaceae
Go to FSUS key
Dig deeper at SERNEC, a consortium of southeastern herbaria.
Check out EDDMapS.org to see where this has been reported.
Read more about Alligator-weed at Vascular Plants of North Carolina.
This plant is a serious weed of natural areas, per Weakley's Flora (2022)
SYNONYMOUS WITH
PLANTS NATIONAL DATABASE:
Alternanthera philoxeroides
FAMILY
Amaranthaceae
SYNONYMOUS WITH Floristic Synthesis of North America. BONAP (Kartesz, 2021)
Alternanthera philoxeroides
SYNONYMOUS WITH Flora of North America
Alternanthera philoxeroides
SYNONYMOUS WITH VASCULAR FLORA OF THE CAROLINAS (Radford, Ahles, & Bell, 1968) 066-01-002:
Alternanthera philoxeroides FAMILY Amaranthaceae
SYNONYMOUS WITH Manual of the Southeastern Flora (Small, 1933, 1938)
Achyranthes philoxeroides
COMMON NAME:
Alligator-weed
To see larger pictures, click or hover over the thumbnails.
)
USDA-NRCS PLANTS Database / USDA Wetland flora: Field office illustrated guide pnd_alph_003_lvd
)
Richard and Teresa Ware rtw_a_philoxeroides
June
Small, white, rounded cloverlike clusters of tiny flowers are 0.5-0.7" wide, per A Field Guide for the Identification of Invasive Plants in Southern Forests (Miller, Chambliss, & Lowenstein, 2010).
COMPARE
aquatic plants
)
JK Marlow jkm160914_110
September
SE-EPPC Aquatic Plant ID Workshop
)
James H. Miller, USDA Forest Service, Bugwood.org bug_1539028
Month Unknown
Leaves somewhat succulent, obtuse to rounded at the tip, per Weakley's Flora (2012).
)
Gary Buckingham, USDA Agricultural Research Service, Bugwood.org bug_4723003
Month Unknown
Each flower w 5 minute petals (actually sepals) surrounding yellow anthers, per A Field Guide for the Identification of Invasive Plants in Southern Forests (Miller, Chambliss, & Lowenstein, 2010).
)
Julia Scher, Federal Noxious Weeds Disseminules, USDA APHIS ITP, Bugwood.org bug_5376307
Month Unknown
)
James H. Miller, USDA Forest Service, Bugwood.org bug_5379494
Month Unknown
)
James H. Miller, USDA Forest Service, Bugwood.org bug_5422002
Month Unknown
)
Nancy Loewenstein, Auburn University, Bugwood.org bug_5471274
Month Unknown
Bracts not keeled. Peduncles 1-7cm, from the leaf axils or terminal, per Weakley's Flora (2012).
WEAKLEY'S FLORA OF THE SOUTHEASTERN US (4/24/22):
Alternanthera philoxeroides
FAMILY
Amaranthaceae
SYNONYMOUS WITH
PLANTS NATIONAL DATABASE:
Alternanthera philoxeroides
FAMILY
Amaranthaceae
SYNONYMOUS WITH
Floristic Synthesis of North America. BONAP (Kartesz, 2021)
Alternanthera philoxeroides
SYNONYMOUS WITH
Flora of North America
Alternanthera philoxeroides
SYNONYMOUS WITH
VASCULAR FLORA OF THE CAROLINAS (Radford, Ahles, & Bell, 1968) 066-01-002:
Alternanthera philoxeroides
FAMILY
Amaranthaceae
SYNONYMOUS WITH
Manual of the Southeastern Flora (Small, 1933, 1938)
Achyranthes philoxeroides
2937
Emergent aquatic (rooted along shoreline, but floating mats can detach); Forb
Perennial
Habitat: Floating in mats on the surface of the waters of blackwater rivers, sloughs, ditches, ponds, and in very moist soil of ditches and shores, per Weakley's Flora
Non-native: tropical America
Common in Coastal Plain, uncommon in Piedmont, rare in Mountains
Click here to see a map, notes, and images from Weakley's Flora of the Southeastern US.
Click here to see a map showing all occurrences known to SERNEC, a consortium of southeastern herbaria. (Zoom in to see more detail.)
This plant is causing problems in natural areas outside its native range, according to authorities such as:
- Alabama Invasive Plant Council, 2012
- Georgia Exotic Pest Plant Council, 2006
- Kentucky Exotic Pest Plant Council, 2013
- Mid-Atlantic Exotic Pest Plant Council
- NC Department of Transportation
- SC Department of Natural Resources Aquatic Nuisance Species List, 2003
- SC List of Regulated Pest Plant Species, 2017
- Tennessee Exotic Pest Plant Council, 2009
- US Forest Service Southern Research Station
- Virginia Department of Conservation and Recreation, 2014
LEAVES:
Simple
Opposite
FLOWER:
Spring/Summer/Fall
White
Bisexual
5 sepals
Petals absent
5 stamens, united at base
FRUIT:
Spring/Summer/Fall
Utricle
TO LEARN MORE about this plant, look it up in a good book!
- Field Guide to Aquatic Plants of Alabama (Lovell, 2007) p07
- Guide to the Wildflowers of SC (Porcher & Rayner, 2001) p374
- Invasive Plants, Guide to Identification, Impacts and Control (Kaufman & Kaufman, 2007) p422
- A Field Guide for the Identification of Invasive Plants in Southern Forests (Miller, Chambliss, & Lowenstein, 2010) p098
- Invasive Exotic Plants of North Carolina (Smith, 2008) p052
- Wildflowers of the Atlantic Southeast (Cotterman, Waitt, & Weakley, 2019) p210
- Wildflowers of the Carolina Lowcountry (Porcher, 1995) p098
- Wildflowers of Tennessee (Carman, 2005) p052
- Wildflowers of Tennessee, the Ohio Valley, and the Southern Appalachians (Horn, Cathcart, Hemmerly, & Duhl, 2005) p074