Tungoil Tree (Vernicia fordii)
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Miller, J.H., E.B, Chambliss, N.J. Loewenstein. 2010. A Field Guide for the Identification of Invasive Plants in Southern Forests. General Technical Report SRS-119. Asheville, NC. United States Department of Agriculture, Forest Service. 126 p.
Contents |
Plant
Deciduous tree (leaves fall with frost) to 40 feet (12 m) in height having a rounded crown with many alternate branches and basal sprouts. Sap is milky white. Leaves heart shaped, some with rounded sinuses, and long petioles with a pair of conspicuous dark glands where joining the blade. Clusters of showy, white and rose, flaring flowers in spring yield large spherical “nuts” in the fall. Caution: Leaves and nuts are poisonous.
Stem
Twigs moderately stout, often radiating outward in numbers from a swollen branch knot that terminates each year’s growth. The branch knot has multiple leaf and fruit stem scars along with numerous protruding light dots. Twigs light green, becoming mottled with a silvery-gray film and turning grayish to gray tan with whitish dots (lenticels) that turn to faint lengthwise stripes that increase with age. Buds overlapping, maroon, with multiple, leafy scales. Pith white and spongy. Leaf scars circular when whorled or oval when stacked together. Larger scars reveal 8 vascular bundle scars. Bark light tan to light gray, tight, covered with corky dots.
Leaves
Alternate but more clustered at twig tips, heart shaped, 3 to 14 inches (7.5 to 35 cm) long with 1 tip, or lobed with deep sinuses and 3 to 5 pointed tips and a cordate base. Two rounded, dark reddish-maroon glands occur where the petiole joins the blade. Glossy and dark green above with 5 prominent light-green veins radiating from the base, whitish silvery beneath. Petioles 3 to 6 inches (8 to 15 cm) long, green with a maroon tinge. Leaves turning yellow in the fall with showy maroon petioles and lower veins.
Flowers
March to April. Large, terminal branched clusters of separate male and female flowers appearing before leaves to cover the tree. Widely flared flowers about 1 inch (2.5 cm) wide having 5 to 7 brilliant white petal lobes splashed with red to maroon within the throat radiating outward in lines, and protruding yellow floral parts. Stalks to 6 inches (15 cm) long, smooth, red to orange, the same color as the sepals.
Fruit and seeds
September to November. Large, spherical, woody nuts (drupes), 2 to 3 inches ( 5 to 8 cm) wide, dark green turning maroon to finally brown, dropping whole to the ground or water to split into 3 to 7 wedged-shaped, fibrous sections each with a large brownish nut, about 1 inch (2.5 cm) long.
Ecology
Rapid growing in moist and well-drained soils, forming dense stands. When first introduced, fruit could not withstand freezing temperatures, until crop breeding yielded frosthardy varieties. Colonizes by stump sprouts and spreads by animal- and water-dispersed seeds. Viable seed can be produced at 3 years.
Resembles
Resembles paper mulberry [Broussonetia papyrifera (L.) L’Hér. ex Vent], southern catalpa (Catalpa bignonioides Walt.), northern catalpa [C. speciosa (Warder) Warder ex Engelm.], and princesstree [Paulownia tomentosa (Thunb.) Sieb. & Zucc. ex Steud.], which have similar shaped leaves but are velvety or rough hairy and have no petiole glands. Also resembles Chinese parasoltree [Firmiana simplex (L.) W. Wight], which has similar shaped leaves with sinuses but has no glands and no milky sap.
History and use
Initially introduced in 1905 from China with further introductions to the lower Gulf Coast States for use in the tungoil industry, which collapsed by the 1950s due to freezes, hurricanes, and offshore competition. Sparingly planted as an ornamental for the showy flowers.
Distribution
Found in dense infestations in LA and the southern portions of MS, AL, and GA, and north FL. Scattered occurrence northward from ornamental plantings.
Management strategies
- Do not plant. Remove prior plantings, and control sprouts and seedlings. Bag and dispose of fruit in a dumpster or burn.
- Treat when new plants are young to prevent seed formation.
- Cut, mulch, and bulldoze when fruit are not present.
- Manually pull new seedlings and tree wrench saplings when soil is moist, ensuring removal of all roots.
- Burning treatments are suspected of having minimal topkill effect due to scant litter.
Recommended control procedures
Large trees and saplings. Make stem injections using undiluted Garlon 3A (June through September) when safety to surrounding vegetation is desired or Vanquish* as a 75-percent solution (9 quarts per 3-gallon mix) with water (June through October) in cut-spacings specified on the herbicide label. For stems too tall for foliar sprays, cut and immediately treat the stump tops with one of the following herbicides: Garlon 4 as a 25- to 50-percent solution (3 to 6 quarts per 3-gallon mix) or Garlon 3A as a 30-percent solution (7 pints per 3-gallon mix). ORTHO Brush-B-Gon, Enforcer Brush Killer, and Vine-X are effective undiluted for treating cut-stumps and available in retail garden stores (safe to surrounding plants).
Saplings. When safety to surrounding vegetation is desired, apply a basal spray of Pathfinder II undiluted. Otherwise, use Garlon 4 as a 20-percent solution (5 pints per 3-gallon mix) in a labeled basal oil product, vegetable oil or mineral oil with a penetrant, or fuel oil or diesel fuel (where permitted). Elsewhere, apply Stalker* as a 6- to 9-percent solution (1.5 to 2 pints per 3-gallon mix) in a labeled basal oil product, vegetable oil or mineral oil with a penetrant, or fuel oil or diesel fuel (where permitted).
Seedlings and saplings. Wet all leaves on young trees < 10 feet (3 m) tall using one of the following herbicides in water with a surfactant: Garlon 3A as a 2-percent solution (8 ounces per 3-gallon mix), a glyphosate herbicide as a 2- to 3-percent solution (8 to 12 ounces per 3-gallon mix) when safety to surrounding vegetation is desired, Chopper Gen2* as a 1-percent solution (4 ounces per 3-gallon mix), or Arsenal AC* as a 0.5-percent solution (2 ounces per 3-gallon mix).
* Nontarget plants may be killed or injured by root uptake.
Images
 Photo by James H. Miller, USDA Forest Service, Bugwood.org June |  Photo by James H. Miller, USDA Forest Service, Bugwood.org October |  Photo by James H. Miller, USDA Forest Service, Bugwood.org June |  Photo by James H. Miller, USDA Forest Service, Bugwood.org October |
 Photo by James H. Miller, USDA Forest Service, Bugwood.org October |  Photo by James H. Miller, USDA Forest Service, Bugwood.org April |  Photo by James H. Miller, USDA Forest Service, Bugwood.org November |  Photo by James H. Miller, USDA Forest Service, Bugwood.org June |
 Photo by James H. Miller, USDA Forest Service, Bugwood.org June |  Photo by James H. Miller, USDA Forest Service, Bugwood.org February |
