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Common Name:
WATER SMARTWEED
Synonym:
Polygonum amphibium
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Coefficient of Conservatism:
6
Coefficient of Wetness:
-5
Wetness Index:
OBL
Physiognomy:
Nt P-Forb
M. Demmon
Polygonum amphibium of Michigan Flora.
Lakes and ponds, permanent or ephemeral; river margins and quiet backwaters, marshes; “terrestrial” forms in drier ground nearby (or after lowering of water levels).
Variety amphibia is native to in the Old World; we have two native intergrading entities sometimes distinguished as varieties, as follows:
(a) var. stipulacea (N. Coleman) H. Hara. Stems prostrate, in water (up to 2 m deep) producing flowering shoots with floating leaves (superficially resembling those of a Potamogeton). Young terrestrial shoots with a ± horizontal green flange at the summit of the ocrea, seldom flowering. (Both types of shoot may be found on a single stem which extends from a terrestrial to an aquatic habitat.) Inflorescence ± ovoid or conic, 1.5–3 (–4) cm long. This variety occurs throughout the state.
(b) var. emersa (Michx.) J. C. Hickman. Stems ± erect, even when in the water. Floating leaves not produced. Ocreae without green flange. Inflorescence ± cylindrical, at least 3–8 cm long. This variety apparently occurs only very rarely north of the Straits of Mackinac in Michigan, though it is common in the southern Lower Peninsula.