Pilea

Scientific name

Pilea Lindl.

Common names

clearweed

Family

Urticaceae

Similar genera

Aciotis, Fittonia, Hemigraphis

Native distribution

tropical and subtropical regions worldwide, except Australia and New Zealand

Species cultivated

Several species and numerous varieties are cultivated.

Pilea cadierei Gagnep. & Guillaumin is the most commonly encountered.

Adventive distribution

introduced into Australia

Weed status

may be weedy

Habit

helophytic, often succulent herbs, subshrubs, or rarely shrubs

Brief description

Small to medium. Stems erect or ascending, simple or branched; stipules between the stem and petiolepetiole:
(n) the stalk of a leaf
. Leaves oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, decussatedecussate:
(adj) arranged along stem in pairs, with each pair at right angles to the pairs above and below
, pairs equal or unequal; petiolatepetiolate:
(adj) relating to or in the form of a petiole; bearing petioles
; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
typically ellipticalelliptical:
(adj) in the form of an ellipse (oval)
, oblongoblong:
(adj) two to four times longer than wide, with +/- parallel sides
or ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, sometimes bullatebullate:
(adj) having a pimpled or blistered surface
; apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
round to acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
; marginmargin:
(n) edge; rim
entireentire:
(adj) having a continuous margin that is not toothed or lobed
or dentatedentate:
(adj) (of a leaf margin) (1) toothed; (2) bearing shallow teeth projecting outward from midrib
; 3-veined, or pinnatepinnate:
(adj) in the form of a feather; of, e.g., leaflets, lobes, or veins: arranged in two rows along an axis
; cystoliths linear, conspicuous. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
an axillaryaxillary:
(adj) in, of, or produced from an axil
cyme or paniclepanicle:
(n) an indeterminate, branched (often much-branched) inflorescence; the ultimate units may be of a different inflorescence type
; bracts small; flowers sessilesessile:
(adj) attached directly, without a stalk
. Male flower tepals typically 4, often bearing a small horn near apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
; stamens 4. Female flower tepals typically 3, equal or sometimes 1 enlarged and hoodlike; staminodes 3, scale-like, oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
tepals; stigmastigma:
(n) the portion of the pistil that is receptive to pollen
sessilesessile:
(adj) attached directly, without a stalk
, with small tufts of hair.

Natural habitat

humid, moist to wet, shaded areas; commonly found among rocks on margins of bodies of water (streams, brooks, rivers, etc)

Additional comments

A large genus with over 250 helophytic species, none of which are true aquatics. Several species are cultivated as house plants, or for terraria or ripariums; Pilea cadierei is the most common species used in ponds and aquariums.