Tropical Soda Apple
Solanum viarum Dunal

Miller, James H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. Gen. Tech. Rep. SRS–62. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p.

Plant. Upright, thorny perennial subshrub or shrub, 3 to 6 feet (1 to 2 m) in height, with leaves shaped like oak leaves, clusters of tiny white flowers, and green-to-yellow golf-ball size fruit. Fruit sweet smelling and attractive to livestock and wildlife. Remains green over winter in most southern locations.

Stem. Upright-to-leaning, much branched, hairy, covered with broad based white-to-yellow thorns. Leaves. Alternate, 4 to 8 inches (10 to 20 cm) long and 2 to 6 inches (5 to 15 cm) wide. Margins deeply lobed (shaped like oak leaves). Velvety hairy with thorns projecting from veins and petioles. Dark green with whitish midveins above and lighter green with netted veins beneath.

Flowers. May to August (year-round in Florida). Terminal small clusters of five-petaled white flowers. Petals first extended, then becoming recurved. Yellow-to-white stamen projecting from the center.

Fruit and seeds. June to November (year-round in Florida). Spherical, hairless, pulpy berry 1 to 1.5 inches (2.5 to 4 cm). Mottled green ripening to yellow. Each berry producing 200 to 400 reddish-brown seeds.

Ecology. Occurs on open to semishady sites. Viable seed in green or yellow fruit but not in white fruit. Reaches maturity from seed within 105 days. Persists by green stems or rootcrowns in warmer areas. Rapidly spreading by cattle and other livestock transportation and by wildlife-dispersed seeds as well as seed-contaminated hay, sod, and machinery.

Resembles horsenettle, S. carolinense L., an 8- to 30-inch (20- to 80-cm) forb, which has similar but smaller fruit, long elliptic-to-ovate lobed leaves 3 to 5 inches (8 to 12 cm) long and 1 to 3 inches (2.5 to 8 cm) wide, and prickly yellow spines on stems and lower leaf veins.

History and use. Native to Argentina and Brazil and introduced into Florida in the 1980s. No known use. A Federal listed noxious weed with an eradication program underway.

Recommended control procedures for isolated sightings:

• Thoroughly wet leaves and stems with one of the following herbicides in water with a surfactant at times of flowering before fruit appear: Garlon 4 (or Remedy in pastures) or Arsenal AC* as a 2-percent solution (8 ounces per 3-gallon mix); a glyphosate herbicide as a 3-percent solution in water (12 ounces per 3-gallon mix).
• Collect and destroy fruit to prevent reestablishment.
• If mowing is used to stop fruit production, delay herbicide applications until 50 to 60 days to ensure adequate regrowth.

*   Nontarget plants may be killed or injured by root uptake.

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