Pilea is the genus name of more than 600 species of the family Urticaceae. Although most of these plants are native to tropical and subtropical regions — such as Vietnam where the popular houseplant aluminum plant, P. cadierei, is native — the Canadian clearweed, P. pumila, and other nettles are native to North America. Pilea are shade-loving succulents that normally have attractive foliage. For example, the aluminum plant has shiny, aluminum-like markings on dark green, crinkly leaves. Various pilea plants are raised as houseplants, including the friendship plant, P. involucrata, and the Chinese money plant, P. peperomioides.
The ideal growing temperature for pilea plants is 70° Fahrenheit (about 21° Celsius), but no colder than 55° Fahrenheit (about 13° Celsius). They are tropical plants, therefore they do best in a humid area. A grower may raise the humidity around the plant by setting it on stones in a dish of water. The plant will rot if the pot sits in the water; therefore, the stones should hold it above the water. Various small pilea plants thrive in terrariums due to their shallow root systems and need for humidity.
As a tropical plant, most of them grow on the forest floor and are shaded by tree canopies, therefore they do not tolerate direct, intense sunlight. Indoors, they grow best in a north window or away from a southern window. These plants normally survive under artificial light, such as in an office area.
Some upright, bushy types of pilea need regular pruning to keep the round shape and to discourage legginess, which usually comes with age. Others are trailing plants, such as the creeping Jenny, P. depressa, and creeping Charlie, P. nummulariifolia, varieties. The artillery plant, P. microphylla, is often grown as a ground cover in warmer regions, such as Texas in the United States, but frequently becomes invasive if the gardener is not vigilant at keeping it controlled.
Friendship plant, P. involucrata, is an upright variety that has attractive, deeply textured, burgundy and green leaves. This plant should not be confused with Billbergia nutans, which is also called friendship plant. Like most pilea plants with textured leaves, the deeply creased leaves of the P. involucrata lose their texture as the plant ages.
Although the US Food and Drug Administration (FDA) and the governments of many other countries do not accept or support the use of folk medicines, tea made from P. muscosa leaves is used for a variety of ailments, including diarrhea. Some Malaysian natives use P. microphylla to treat wounds and scientists are studying it for its antioxidant and antibacterial qualities. A person needs to know which plants are safe for ingestion before making home remedies; numerous pilea plants, called nettles, have stinging hairs that can cause skin irritation on contact.