Trifoliate Orange, Hardy Orange (Poncirus trifoliata)
From Bugwoodwiki
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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, small tree or shrub to 20 feet (6 m) in height with tufts of trifoliate (3-leaflet) leaves on densely packed stems with dangerously sharp axillary thorns. White flowers in spring cover plants to yield abundant small, fuzzy green orange-like fruit that turn yellow in fall. Root sprouts abundant around stems.
Stem
Twigs flattened, glossy green and hairless, turning yellowish in drought and winter, becoming stout, chestnut brown to reddish tan, smooth to velvety with light dots (lenticels), heart-shaped leaf scars and sharp thorns jutting outward to 2 inches (5 cm). Buds finely hairy, dome-shaped, and partially hidden by the leaf bases. Branches dark gray with lengthwise lighter stripes and intervening green stripes that become an intricate braided network on the bark. Basal sprouts vinelike and green, climbing up through the crown into surrounding trees.
Leaves
Alternate or tufts of trifoliate (3-leaflet) leaves in the axils of thorns, appearing at or just after the time of flowering in the spring. Leaflets unequal in size with the terminal 1 to 2.5 inches (2.5 to 6.4 cm) long and 0.5 to 1 inch (1.2 to 2.5 cm) wide, obovate to elliptic, while the lateral leaflets are similar but smaller. Dark green and hairless, becoming yellowish in the fall. Blades merge into the winged leaf stalk (sometimes not winged).
Flowers
March to early May. Showy clusters of white, 5-petaled flowers, 1.5 to 2 inches (3.8 to 5 cm) across that cover trees early on previous year’s branches. In the center of the flower are 8 to 10 projecting stamens that enclose a yellow, hairy stigma.
Fruit and seeds
July to October and rarely persisting into winter. A hairy, bitter orange, green turning yellow to golden when ripe, up to 1.5 inches (3.8 cm) wide. Pulp is minimal and the multiple seeds are viable.
Ecology
Moderate initial growth rate becoming rapid with establishment, forming dense, impenetrable thickets and stands. Prefers open areas or edges and acid, well-drained soils. Colonizes by basal sprouts and spreads by prolific animal-dispersed seeds.
Resembles
Resembles osage-orange [Maclura pomifera (Raf.) C.K. Schneid.], which has similar thorny stems, but larger, spherical yellowish fruit that are not hairy and leaves that are not trifoliate.
History and use
Introduced as an ornamental in the 1850s from China and Korea. Fruits are useful for extraction of acidic juice high in vitamin C. Used as a hearty rootstock for grafted citrus. Historically planted as a thorny hedge to confine livestock.
Distribution
Found in scattered dense infestations in TX, OK, AR, LA, and GA with occasional occurrences elsewhere throughout the region except KY.
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 and bulldoze when fruit are not present.
- Anticipate wider occupation when plants are present before disturbance.
- Cutting, tree injection, manual pulling, and tree wrenching are hindered by dense thorny branches and basal sprouts so use eye protection.
- 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.
- Treatment combinations should be used that are appropriate for dense thickets with limited access. Access trails may need to be cut.
Recommended control procedures
Large trees and saplings. Cut and immediately treat the stump tops with one of the following herbicides: a glyphosate herbicide or Garlon 3A as a 25-percent solution (3 quarts per 1-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). A subsequent foliar application may be required to control new seedlings and resprouts.
Saplings. When safety to surrounding vegetation is desired, apply a basal spray of either Pathfinder II undiluted or 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. When safety to surrounding vegetation is desired, thoroughly wet all leaves with a glyphosate herbicide or Garlon 3A as a 4-percent solution (1 pint per 3-gallon mix) in water with a surfactant; or if nontarget damage is not a concern, apply 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 October |  Photo by James H. Miller, USDA Forest Service, Bugwood.org July |  Photo by James H. Miller, USDA Forest Service, Bugwood.org March | |
 Photo by James H. Miller, USDA Forest Service, Bugwood.org May |  Photo by James H. Miller, USDA Forest Service, Bugwood.org March |  Photo by James H. Miller, USDA Forest Service, Bugwood.org March |  Photo by James H. Miller, USDA Forest Service, Bugwood.org March |
