Botanical name: Alternanthera philoxeroides Family: Amaranthaceae (Amaranth family)
Synonyms: Bucholzia philoxeroides, Achyranthes paludosa, Achyranthes philoxeroides
Alligator weed is an immersed aquatic plant. It originated in South America, but has spread to many parts of the world and is considered an invasive species in Australia, China, New Zealand, Thailand and the United States. It is a sprawling herb, usually in water, often in row crops and gardens. Stems are pinkish, can become hollow when larger, up to 3.3 ft long. Leaves are opposite, narrowly elliptic or spatulate, up to 9 cm long; occasionally a few indistinct teeth on margin. Flowers are reduced, bisexual in round white heads on long stalks from upper leaf axils. Each flower has 4-5 thin, papery bracts, 5 stamens, 1 pistil. Fruit is tiny, one-seeded, thin-walled.
Identification credit: Navendu Pagé
The flower labeled Alligator Weed is ...