Spermacoce prostrata Aubl., Rubiaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Borreria prostrata (Aubl.) Miq.

Common name(s): [more details]

Chinese: pu fu feng hua cao

English: false buttonweed, prostrate false buttonweed

Spanish: botoncillo

Habit:  herb

Description:  "Prostrate or decumbent annual herbs to 40 cm tall, branching mostly near the bases, leafy stems 0.4-2 mm thick, glabrous or rarely with thin hairs to 0.8 mm long, with 4 longitudinal ribs 0.1-0.3 mm high; stipule sheaths 1-3 mm high, 1.5-6 mm broad, with 3-9 awns 1-2 mm long. Leaves opposite or pseudoverticillate with 2-4 smaller axillary leaves at each node, sessile or subsessile; leaf blades 10-35 mm long, 2-18 mm broad, elliptic to narrowly elliptic or elliptic-lanceolate, apex acute (obtuse), base cuneate and decurrent on petiole, drying membranaceous to chartaceous, greenish or yellowish brown, glabrous or with minute (0.2 mm) stiff hairs above and below, scabrous on the margin, 2§ veins 2-4/side. Inflorescences mostly axillary (sometimes terminal), 2-4 mm high and 3-8 mm broad, flowers few (3-8) to many (ca. 20) and sessile. Flowers with hypanthium 0.5-1 mm long, calyx lobes usually 2 larger and 2 smaller, 0.6-1 mm long; corolla white, less than 3 mm long. Fruits ca. 2 mm long, body of the fruit 0.8-1.2 mm long; seeds 0.7-1.2 mm long, 0.3-0.5 mm broad, reticulate, often with longitudinal ridges (x 10) and distinctive transversely elongated pits (x40), dark reddish brown" (Berger, 1993; p. 318).

"Spermacoce prostrata is recognized by the small weedy habit, usual lack of puberulence, often sessile leaves, minute flowers, and small seeds with reticulated surface of distinctive pits. These pits are larger (0.05-0.1 mm) than in S. exilis or S. ovalifolia and they are transversely oblong (x40)... The fruits usually appear to have only two calyx lobes because the two smaller lobes fall off. Many of these specimens were earlier placed under the name Borreria ocymoides (Burm.) DC., an Asian species. Compare with S. exilis" (Berger, 1993; p. 318).

A key to some Spermacoce species (adapted from Lorence & Flynn, 2006; pp. 4-5):

1.  Mature seed surface with deep transverse grooves, the surface between grooves foveolate:  Spermacoce remota [=Spermacoce assurgens].
1.  Mature seeds with surface variously sculptured but not transversely grooved:  2

2(1).  Calyx lobes consistently 2:  Spermacoce exilis
2.       Calyx lobes 4 (occasionally 2-3 in some flowers of Spermacoce prostrata):  3

3(2).  Leaves, at least the lower ones, distinctly petiolate with petioles 5-10 mm long; corolla tube c. 4-5 mm long; capsule (excluding calyx) 2.5-3.0 mm long; seeds 2.0-2.6 mm long:  Spermacoce latifolia
3.      Leaves sessile or the lower ones with petioles 1-3 (5) mm long; corolla tube 0.5 mm long; capsule (excluding calyx) 1-2 mm long; seeds 0.7-1.8 mm long:  4

4(3).  Calyx lobes 4 (occasionally 2-3 in some flowers), 0.5-0.7 mm long, deltate to narrowly deltate with green midrib and broad pale margins; capsule 1.0-1.1 mm long; seeds 0.7-0.9 mm long, deep purplish-brown, dorsal surface with fewer than 8 vertical rows of deep, circular-rimmed pits:  Spermacoce prostrata
4.      Calyx lobes 4, 0.4-1.1 mm long, narrowly deltate to linear-subulate with green midrib and narrow pale margins; capsule 1.2-2.0 mm long; seeds 1-1.8 mm long, chestnut to purplish-brown, dorsal surface with more than 10 vertical rows of minute, shallow pits:  Spermacoce ovalifolia

Habitat/ecology:  "Common weedy plants of open sites in evergreen and partly deciduous forest regions (only rarely collected in deciduous forest areas), from near sea level to 1900 m elevation" (Berger, 1993; p. 318).

Propagation:  Seed

Native range:  "Southern United States to South America and the West Indies" (Berger, 1993; p. 318).

Presence:

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	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)
China China	China (People's Republic of)	introduced invasive	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Naturalized in disturbed wet sites at low elevations. Hainan, Hong Kong.
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 187)
Mexico Mexico	Mexico (United Mexican States)	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)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan Taiwan Island	Taiwan Island	introduced invasive	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Naturalized in disturbed wet sites at low elevations.

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  Hawaiian species originally misidentified as Spermacoce ovalifolia (Lorence et al., 1995; p. 52).

Control:  If you know of control methods for Spermacoce prostrata, please let us know.