Pilea

Pilea
Pilea rotundinucula
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Rosales
Family:	Urticaceae
Genus:	Pilea Lindl., 1821
Species
See text.

Pilea, with 600–715 species, is the largest genus in the plant family Urticaceae and one of the larger genera in the Urticales and eudicot rosids.

It is distributed throughout the tropics, subtropics, and warm temperate regions (with the exception of Australia and New Zealand).

The majority of species are succulent shade-loving herbs or shrubs, which are easily distinguished from other Urticaceae by the combination of opposite leaves (with rare exceptions) with a single ligulate intrapetiolar stipule in each leaf axil and cymose or paniculate inflorescences (again with rare exceptions).

Pilea is of little economic importance; six species have horticultural value (P. cadierei, P. grandifolia, P. involucrata, P. microphylla, P. nummulariifolia, and P. peperomioides),^[1] and one species is used in Chinese traditional medicine (P. plataniflora). The genus has attracted little monographic attention since Weddell (1869), and the majority of taxonomic contributions have come from floristic treatments. To date, 787 species names have been published (International Plant Names Index, 2003) and estimates for the species number range from 250 to 1000.^[2] Based on previous floristic treatments, about 30% of the species from regions not yet covered by contemporary floristic treatments may be undescribed.

The genus name is derived from Latin pileus, "felt cap", because of the calyx covering the achene.

Species include

• Pilea cadierei - aluminium plant
• Pilea cataractae
• Pilea cavernicola
• Pilea crassifolia
• Pilea depressa - creeping Jenny
• Pilea fontana
• Pilea glauca - silver sprinkles
• Pilea grandifolia
• Pilea involucrata - friendship plant
• Pilea jamesonia
• Pilea laevicaulis
• Pilea matama
• Pilea microphylla - artillery plant, gunpowder plant
• Pilea mollis - Moon Valley plant
• Pilea myriantha
• Pilea myriophylla
• Pilea napoana
• Pilea nummulariifolia - creeping Charlie
• Pilea peperomioides - Chinese money plant, missionary plant
• Pilea pollicaris
• Pilea pumila - Canadian clearweed
• Pilea repens - black-leaf panamiga
• Pilea riopalenquensis
• Pilea schimpfii
• Pilea selbyanorum
• Pilea serpyllacea
• Pilea serratifolia
• Pilea topensis
• Pilea trianthemoides
• Pilea trichosanthes
• Pilea trilobata
• Pilea tungurahuae

References

1. RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964.
2. (C. D. Adams, BM, personal communication).

• Britton, N.L. and Brown, A. (1913) An Illustrated Flora of the Northern United States and Canada. In three volumes. Dover Publications. ISBN 0-486-22642-5, page 634
• Fouler Rhoads, A. and Block, T.A. (2000). The Plants of Pennsylvania. University of Pennsylvania Press. ISBN 0-8122-3535-5, page 694.
• Hortus Third, pages 872-873
• Monro, A.K. (2006). The revision of species-rich genera: a phylogenetic framework for the strategic revision of Pilea (Urticaceae) based on cpDNA, nrDNA, and morphology. American Journal of Botany 93:426-441. HTML
• Monro, A.K. (2009). A new species of Pilea(Urticaceae) from the Talamanca Mountains, Costa Rica. Phytotaxa 2: 24-28.
• Strausbaugh P.D. and Core, E.L. (1964). Flora of West Virginia. 2nd ed. Seneca Books Inc., ISBN 0-89092-010-9, pages 318-319
• Weddell H.A. (1869). Pilea. In A. De Candolle [ed.], Prodromus systematis naturalis regni vegetabilis 16, 104–163. Victoris Masson, Paris, France.
• USDA U.S. Dept. of Agriculture Plants Database

Further reading

• Chen, C. J. (1982). A monograph of Pilea (Urticaceae) in China. Bull. Bot. Res., Harbin 2: 1-132.
• Monro, A.K. (2006). The revision of species-rich genera: a phylogenetic framework for the strategic revision of Pilea (Urticaceae) based on cpDNA, nrDNA, and morphology. American Journal of Botany 93:426-441.