Flora of North America species comparison

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Pilea microphylla

Pilea

artillery plant, artillery weed, pistol plant, rockweed

clearweed
Habit Herbs, annual or short-lived perennial, 0.3-2 dm. Herbs, shrubs, or subshrubs, annual or perennial, glabrous.
Stems

10-40-branched, erect.

simple or branched, erect, ascending, or repent.
Leaves

blades spatulate to obovate, paired blades unequal, the larger 3-10 × 1.5-5.5 mm, the smaller 1.5-4 × 0.7-2 mm, margins entire.

blades paired, equal or unequal, ovate, margins dentate or entire;

cystoliths linear, ± conspicuous.
Inflorescences

crowded.

axillary, compact to lax cymes.
Flowers

ca. 0.5 mm across.

unisexual, staminate and pistillate flowers in same cyme;

bracts deltate to linear.
Staminate flowers

tepals 4;

stamens 4;

pistillode conic.
Pistillate flowers

tepals 3, equal or sometimes 1 tepal enlarged and hoodlike;

staminodes 3, opposite tepals, under tension and ejecting mature achene;

style and tufted stigma deciduous.
Achenes

uniformly light brown, slightly compressed, ovoid-cylindric, ca. 0.5(-1.1) × 0.3 mm, smooth.

sessile, laterally compressed, ovoid to teardrop-shaped, free from perianth at maturity, partly covered by hoodlike tepal.
x

= 12, 13.

Pilea microphylla

Pilea
Phenology Flowering all year.
Habitat Waste places, hammocks, rocky woods, cultivated plots, on masonry
Elevation 0-100 m (0-300 ft)
Distribution
from FNA
FL; GA; LA; SC; HI; Mexico; Central America; West Indies; tropical South America; Asia
[WildflowerSearch map]
[BONAP county map]
from USDA
Mostly tropical and subtropical regions worldwide except Australia and New Zealand
[BONAP county map]
Discussion

Pilea microphylla has been collected once in Tennessee and once in Michigan, but it is unlikely that the species persists so far north. It is widely grown as a houseplant in the north and a border plant in the south. It is a greenhouse weed in various parts of the flora.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species ca. 400 (5 in the flora).

Pilea should be further revised.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaf margins dentate; paired blades equal.
→ 2
1. Leaf margins entire; paired blades unequal.
→ 3
2. Achenes uniformly black except for very narrow, pale, marginal band, surface conspicuously pebbled with raised bosses.
P. fontana
2. Achenes uniformly light colored or streaked with purple, surface smooth or purple striations sometimes slightly raised.
P. pumila
3. Stems repent or prostrate.
→ 3
3. Stems erect or diffusely ascending.
→ 4
4. Herbs; leaf blades spatulate to obovate.
P. microphylla
4. Shrubs or subshrubs; leaf blades of 2 types, obovate and orbiculate to orbiculate-cordate.
P. trianthemoides
Source FNA vol. 3. FNA vol. 3.
Parent taxa Urticaceae > Pilea Urticaceae
Sibling taxa
P. fontana, P. herniarioides, P. pumila, P. trianthemoides
Subordinate taxa
P. fontana, P. microphylla, P. pumila, P. trianthemoides
Synonyms Parietaria microphylla Adicea
Name authority (Linnaeus) Liebmann: Naturvidensk. Math. Afd., ser. 5, 2: 296. (1851) Lindley: Coll. Bot., plate 4 and text on facing page. 1821, name conserved
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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