Flora of North America species comparison

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Pilea fontana

clearweed, lesser clearweed
Habit Herbs, annual, 1-7 dm.
Stems

simple or slightly branched, erect.
Leaf

blades elliptic to ovate, paired blades equal, 1-10 × 0.6-4.5 cm, margins dentate.
Inflorescences

crowded or lax.
Flowers

ca. 1 mm across.
Achenes

uniformly black except for very narrow, pale, often inconspicuous, marginal band, compressed, teardrop-shaped, 1.3-1.7 × 1-1.5 mm, conspicuously pebbled or warty with raised bosses.

Pilea fontana
Phenology Flowering late summer–fall.
Habitat Mixed woods, along streams, swamps, seepages, and marshes
Elevation 0-300 m (0-1000 ft)
Distribution
from FNA
AL; CT; FL; GA; IA; IL; IN; MA; MD; MI; MN; NC; ND; NE; NJ; NY; OH; PA; RI; SC; SD; VA; VT; WI; ON
[WildflowerSearch map]
[BONAP county map]
Discussion

Pilea fontana and P. pumila are separated primarily by differences in their mature achenes. In addition, leaves of P. fontana are often more opaque and less shiny than those of P. pumila. A few collections of P. pumila from Bourbon, Owen, and Robertson counties, Kentucky, and Macon County, Tennessee, have the black achenes of P. fontana, but without the bosses, and show striations on the younger achenes as in P. pumila. I have seen only two mixed collections (Chisago County, Minnesota, and Richland-Ransom county line, South Dakota), which probably indicates that these two very similar species seldom occur together, even though their ranges overlap completely.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 3.
Parent taxa Urticaceae > Pilea
Sibling taxa
P. herniarioides, P. microphylla, P. pumila, P. trianthemoides
Synonyms Adicea fontana
Name authority (Lunell) Rydberg: Brittonia 1: 87. (1931)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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