Pilea hyalina Fenzl, Urticaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 8 (Go to the risk assessment)

Habit:  herb

Description:  "Small erect herbs 10-30 cm. tall, bisexual, unbranched or more often with several lateral branches and bush-like form, leafy internodes 4-40 mm. long, 0.4-2.5 mm. thick, glabrous, succulent but drying yellowish and often translucent; stipules rudimentary and less than 1 mm. long, usually obscure. Leaves of the same node of similar size and shape, petioles 4-40 mm. long, 0.2-0.8 mm. thick (dry), glabrous; laminae 0.7-4 (6) cm. long, 0.6-3 (4) cm. broad, ovate to elliptic-ovate or rhombic, acute at the apex, obtuse to abruptly rounded at the base, crenate-serrate or serrate (except near the base) with 3 to 6 teeth per cm., laminae drying membranaceous, upper surface with a few scattered transparent hairs about 0.5 mm. long, the lower surface essentially glabrous, venation palmate with 3 primary veins, midvein with 3 to 7 pairs of obscure secondary veins, short-linear cystoliths usually visible above. Inflorescences in the axils of many nodes and solitary or paired, 3-20 (30) mm. long, short-peduncled but usually much-branched and cymose-paniculate, bisexual but the male flowers soon lost, flowers in congested clusters 1-3 mm. long; male and female flowers about 0.5 mm. long. Fruit 0.3-0.5 mm. long, ovoid to broadly ellipsoid in outline, thick-lenticular with narrowed margins, drying yellowish brown or pale brown"  (Berger, 1977; p. 262).

"Plants annual, the stems erect, mostly simple, succulent and almost transparent, 40 cm. high or less, glabrous; stipules minute, deciduous; leaves of a pair subequal, the slender petioles 4 cm. long or less, the blades thin, rhombic-elliptic or broadly ovate, 1-6 cm. long, 1-3.5 cm. wide, acute, obtuse or broadly cuneate at the base, coarsely serrate, sparsely pilose or villous above, glabrous beneath, with numerous linear cystoliths; flower spikes 2-4 in the axils of almost all the leaves, 2.5 cm. long or less, androgynous, the staminate flowers very few, the pistillate flowers crowded in numerous almost contiguous glomerules; achenes ovate, 0.4 mm. wide"  (Standley and Steyermark, 1952; 24(3)414-415).

Habitat/ecology:  In Costa Rica (native): "plants of seasonally dry or wet evergreen forest formations between (0) 500 and 1800 m.  A succulent-stemmed plant of moist sites and along water courses; completing its life cycle in the wet season"  (Berger, 1977; p. 262).  In Guatemala (native), "moist thickets or forest, frequently a weed in cafetales and other cultivated ground, 250-1,600 meters"  (Standley and Steyermark, 1952; 24(3)414-415).

Propagation:  Seed

Native range:  "Southern Mexico; El Salvador to Panama; tropical South America"  (Standley and Steyermark, 1952; 24(3)414-415).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Lau, Alex/Frohlich, Danielle (2013) (p. 12) Voucher cited: K. Onuma & R. Kihara s.n. (BISH 751164) Found growing in nursey pots shipped from Costa Rica.

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	Burger, W. C. (1977) (p. 262)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	Standley, Paul C./Steyermark, Julian A. (1952) (pp. 24(3)414-415)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Panama (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Colombia	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Carchi, Chimborazo, Guayas, Los Rios
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	Macbride, J. Francis (1936) (p. 13(2/2)343)

Control:  If you know of control methods for Pilea hyalina, please let us know.