*Alternanthera philoxeroides (Martius) Grisebach. Common name: Alligator-weed. Phenology: Mar-Oct. 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. Distribution: Native of tropical America. This plant is a serious weed of natural areas. Reported for s. IN by Bill Thomas (pers.comm., 2022).
Origin/Endemic status: Neotropics
Synonymy ⓘ: = Ar, C, FNA4, Il, K4, NcTx, Ok, RAB, S13, Tn, Tx, Va, WH3; = Achyranthes philoxeroides (Mart.) Standl. — S; = n/a — F, Tat; Bucholzia philoxeroides Martius. Basionym: Bucholzia philoxeroides Mart. 1825
Links to other floras: = Alternanthera philoxeroides - FNA4
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Wetland Indicator Status:
- Atlantic and Gulf Coastal Plain: OBL
- Eastern Mountains and Piedmont: OBL
- Great Plains: OBL
- Midwest: OBL
Heliophily ⓘ: 9
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© Richard & Teresa Ware CC-BY-NC, permission granted to NCBG | Original Image ⭷
© Gary P. Fleming | Original Image ⭷
© Gary P. Fleming | Original Image ⭷
© Gary P. Fleming | Original Image ⭷Feedback
Horticultural Information
Intro: Ascending to reclining, mat-forming, aquatic perennial floating in mats on the surface of blackwater rivers, sloughs, ditches and ponds, and in very moist soil of ditches and shorelines. Native of tropical America.
Stems: Stems stout, mostly hollow, often red-tinged, hairy at the nodes; will root from the nodes, and in standing water will float on the surface, forming a dense, multi-layer mat with upright branches.
Leaves: Leaves opposite, each pair widely spaced and at right angles to the next, sessile, the leaf base forming a sheath around stem at the node, linear to elliptic, 2--4 in. long, obscurely toothed or entire, smooth.
Inforescence:
Flowers: Flowers in compact heads on long stalks coming from upper leaf nodes, white to off-white, tiny, consisting of 5 1/4-in.-long sepals.
Fruits:
Comments: A serious weed of natural areas.
Height: 2-3 ft.
plant sale text:
bloom table text:
description: Ascending to reclining, mat-forming, aquatic perennial floating in mats on the surface of blackwater rivers, sloughs, ditches and ponds, and in very moist soil of ditches and shorelines. Native of tropical America.
stems: Stems stout, mostly hollow, often red-tinged, hairy at the nodes; will root from the nodes, and in standing water will float on the surface, forming a dense, multi-layer mat with upright branches.
leaves: Leaves opposite, each pair widely spaced and at right angles to the next, sessile, the leaf base forming a sheath around stem at the node, linear to elliptic, 2--4 in. long, obscurely toothed or entire, smooth.
inflorescence:
flowers: Flowers in compact heads on long stalks coming from upper leaf nodes, white to off-white, tiny, consisting of 5 1/4-in.-long sepals.
fruits:
comments: A serious weed of natural areas.
cultural notes:
germination code:
native range:
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