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Pilea microphylla

(L.) Liebm. (1851)

This name is accepted

Kingdom: Viridiplantae Phylum: Magnoliophyta Class/Clade: Eudicot-Rosids Order: Rosales Family: Urticaceae Genus: Pilea

artillery plant, gunpowder plant, rockweed

Description

Key Characters:

Growth Form: Annual or short-lived perennial herbs.

Stems: Stems succulent, sometimes slightly woody at base, spreading or cespitose, 5–50 cm long, stems diffuse, branched.

Roots:

Leaves: Leaves simple. Opposite, crowded throughout stem length. Blades obovate, elliptic, oblanceolate, or oblong; 2–10 mm long, 1–4 mm wide, those of a pair very unequal in size, sometimes some branches with leaves of a pair equal or all leaves of plant equal, 1–nerved. Upper surfaces with crowded elliptic cystoliths; lower surfaces finely reticulate. Margins entire. Petioles 1–4 mm long, always shorter than the blade. Stipules ca. 1 mm long.

Flowers: Flowers in sessile glomerules or cymes, peduncles 1–6 mm long. Flowers unisexual (and the plants monoecious or dioecious). Calyx lobes glabrous, each with a blunt, dorsal, apiculate appendage; outer Calyx lobe slightly longer than others with inconspicuous dorsal, apiculate appendages. Corolla (petals) absent. Staminate flowers 0.6–1 mm long; filaments incurved in bud, elastically reflexed when pollen is shed; anthers dithecal, opening by longitudinal slits. Ovary superior (pistillate flowers), 0.8–1 mm long, psuedomonomerous, 1-celled; ovule 1, basal; style 1; staminate flower ovary vestigial and sterile.

Fruit: Achenes uniformly light brown; slightly compressed; ovoid-cylindric; ca. 0.5(-1.1) × 0.3 mm; smooth. Achenes ellipsoid; compressed; 0.5–1 mm long; slightly longer than the largest calyx lobe. Seeds 1 per achene.

Ploidy: 2n = 36

Habitat: Mesic; disturbed areas.

Elevation Range: Low elevation.

Historical Distribution

Uses and Culture

USES

Natural History

Statewide Status

Naturalized

Island Status

Kuaihelani (Midway Atoll) Naturalized
Kaua'i Naturalized
O'ahu Naturalized
Molokai Naturalized
Lana'i Naturalized
Maui Naturalized
Hawai'i Naturalized

Dispersal Agents

Other Animals

Vegetative Reproduction

Pollinators

Bibliography

Name Published In: Mexic. Neldeagt. Pl.: 18 (1851)

Other References

Wagner et al. 1990:1306 (K, O, M, H); Wagner & Herbst 1995:26/Shannon & Wagner 1996:14 (Mi); Oppenheimer & Bartlett 2002:12 (L); Staples & Herbst 2005:553 (KEY), 554 (DESCR); Oppenheimer 2006:14 (Mo)

Occurrences

SNo. Scientific Name Locality Habitat Basis of Record Recorded By Record Number Island Source Date
1 Pilea microphylla east Maui, Makawao District, Makawao, east side of Kailua Gulch Preserved_Specimen Duvall, F. Maui BISH 2012-07-28
2 Pilea microphylla from her yard Preserved_Specimen Suenaga, B. Oahu BISH 1985-06-24
3 Pilea microphylla slopes of Koko crater Preserved_Specimen Christophersen, E. 1298 Oahu BISH 1930-04-06
4 Pilea microphylla Honolulu, Manoa, steps of Pan Pacific Union Preserved_Specimen Brown, F.B.H. 1262 Oahu BISH 1925-06-01
5 Pilea microphylla Bishop Museum Grounds, next to mail trailor beween Paki and Pauahi Moist wet soil collections in asphault under edges of trailor. Preserved_Specimen Crago, L.M. 2005004 Oahu BISH 2005-01-12
6 Pilea microphylla Koele Growing on rocks. Preserved_Specimen Oppenheimer, H.L. 109930 Lanai BISH 1999-10-25
7 Pilea microphylla Honolulu, Kahana Stream (tributary to Makiki stream). Completely channelized area N. of Wilder Ave Growing from crack in masonary wall. Partly sunny area Preserved_Specimen Faccenda, K. 1969 Oahu BISH 2021-06-12
8 Pilea microphylla Honolulu, 4400 Tantalus Dr. wet forest; roadside; with Heliocarpus popayanensis, Impatien. Preserved_Specimen Ray, G. 37 Oahu BISH 1997-08-16
9 Pilea microphylla Honolulu, 42 Coelho Way volunteer in flower pot Preserved_Specimen Neal, M.C. Oahu BISH 1961-06-04
10 Pilea microphylla S of road next to Lumahuli Stream In an abandoned garden with many exotic introdictions. Preserved_Specimen Corn, C. Kauai BISH 1978-06-16
11 Pilea microphylla Pali Preserved_Specimen Kerr, M. Oahu BISH 1945-07-04
12 Pilea microphylla Kailua roadside Preserved_Specimen Kondo, Y. Oahu BISH 1945-06-24
13 Pilea microphylla Hilo, Keaukaha, Richardson's beach rock wall, pavement Preserved_Specimen Cuddihy, L.W. 2067 Hawaii BISH 1987-08-08
14 Pilea microphylla Wailua Game Reserve plots stripmined for bauxite ore in 1958-60. Area variously treated with lime and fertilizer. Now residual pasture. On bare areas and slopes Preserved_Specimen Howard, R.A. 20272 Kauai BISH 1985-10-20
15 Pilea microphylla Bishop Museum Grounds, next to mail trailor beween Paki and Pauahi Moist wet soil collections in asphault under edges of trailor. Preserved_Specimen Crago, L.M. 2005004 Oahu BISH 2005-01-12
16 Pilea microphylla Makawao, highway side of Kanaha Rd disturbed roadside; dominated by grasses, Pluchea indica and P. symphytifolia Preserved_Specimen Wagner, W.L. 5799 Maui BISH 1988-03-03
17 Pilea microphylla East Maui, Keanae Arboretum bare lava and rock walls Preserved_Specimen Hobdy, R.W. 2488 Maui BISH 1986-01-23
18 Pilea microphylla Honolulu, Manoa, Univ. Hawaii campus wayside Preserved_Specimen Egler, F.E. 37425 Oahu BISH 1937-08-26
19 Pilea microphylla W of Kaunakakai Nursery. Preserved_Specimen Oppenheimer, H.L. 40407 Molokai BISH 2004-04-02
20 Pilea microphylla East Maui, Hana, Kauiki, on the eastern side of Hana Bay Terminalia grove behind Community building. Dominated by Casuarina planted in the late 1930's but with numerous other alien species, Terminalia, Syzygium Preserved_Specimen Flynn, T.W. 2514 Maui BISH 1987-10-21
21 Pilea microphylla Lihue cracks in crumbling asphalt Preserved_Specimen Takeuchi, W.N. Kauai BISH 1983-05-01
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