''Pilea pumila'', commonly known as clearweed, Canadian clearweed, coolwort or richweed, is an herbaceous plant in the nettle family (

Urticaceae The Urticaceae are a family, the nettle family, of flowering plants. The family name comes from the genus ''Urtica''. The Urticaceae include a number of well-known and useful plants, including nettles in the genus ''Urtica'', ramie (''Boehmeri ...

). It is native to Asia and eastern North America, where it is broadly distributed. This plant is most often found in rich loamy soil, usually in moist to wet areas. Its natural habitat is in forests or other lightly shaded conditions. It is a common plant throughout its range, and forms large colonies where it is found. It grows in both high-quality habitats and in ecologically degraded areas. Due to its high tolerance for disturbance, it is often seen near buildings and as a garden weed.

Description

''Pilea pumila'' is an erect annual, growing 0.7 to 70 cm tall. The

foliage A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

is opposite, simple with dentate margins, wrinkly (with depressed veins),

ovate Ovate may refer to: *Ovate (egg-shaped) leaves, tepals, or other botanical parts *Ovate, a type of prehistoric stone hand axe *Ovates, one of three ranks of membership in the Welsh Gorsedd *Vates In modern English, the nouns vates () and ovat ...

, and with long petioles. Both the leaves and stems are translucent and bright green, turning bright yellow in autumn. The flowers are small, borne in axillary

cymes An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed on ...

, unisexual with both genders occurring on the same plant, greenish yellow, and

pollinated Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, ...

by wind. Flowers bloom from midsummer through early autumn. Fruits (

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

s) are green with purple markings.

Root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...

s are fibrous, shallow, and

adventitious Important structures in plant development are buds, shoots, roots, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living plant a ...

off the stem in moist areas or when in contact with the soil. The plant is often mistaken for stinging nettle (''

Urtica dioica ''Urtica dioica'', often known as common nettle, burn nettle, stinging nettle (although not all plants of this species sting) or nettle leaf, or just a nettle or stinger, is a herbaceous perennial flowering plant in the family Urticaceae. Ori ...

''), but can be distinguished by the lack of

trichomes Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

, or stinging hairs, and the lower amount of branching of the

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

Taxonomy

Three varieties of ''Pilea pumila'' are currently recognized. They are: *''P. pumila'' var. ''hamaoi'' - Found in China, Japan, and Korea *''P. pumila'' var. ''obtusifolia'' - Restricted to China *''P. pumila'' var. ''pumila'' - Widespread in North America and eastern Asia Among the typical widespread variety ''pumila'', minor differences do exist between the Asian and North American populations. Further taxonomic studies are needed to clarify what level of rank (if any) these differences warrant.

Uses

Canadian clearweed is edible, but unpalatable. The plant can be used in classroom demonstrations of

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...

using food coloring due to its translucent stem. It was reportedly used medicinally by certain Native Americans for sinus issues, itch relief and to reduce hunger, and it is sometimes used as a

diuretic A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics in ...

in Asia.

Ecology

The plant is host to various caterpillars, including the leaf-mining larvae of '' Cosmopterix pulchrimella'', as well as the aphid '' Pseudasiphonaphis corni'' and leafhopper '' Empoasca recurvata''.

References

{{Taxonbar, from=Q1023681 pumila Flora of North America