Silverthorn, Thorny Olive
Miller, James H.; Manning, Steven T.; Enloe, Stephen F. 2010. A management guide for invasive plants in southern forests. Gen. Tech. Rep. SRS–131. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 120 p.
Silverthorn or thorny olive (Elaeagnus pungens Thunb.) is an evergreen, densely bushy shrub 3 to 25 feet (1 to 8 m) in height with long limber projecting shoots that can eventually grow upward spread into tree crowns. Leaves are simple and silver scaly and alternate along shoots with sharp stubby branches, some thorned. Tiny flower clusters appear in fall that yield oblong, red olivelike fruit covered in brown scales in spring. Spreads by animal-dispersed seeds and occurs as scattered individuals, both in the open and under forest shade. Shrubs rapidly increase in size by prolific stem sprouts. Widely planted as an ornamental shrub and infrequently planted for wildlife food.
Management strategies
- Do not plant. Remove prior plantings, and control sprouts and seedlings. Bag and dispose of fruit in a dumpster.
- Treat when new plants are young to prevent seed formation.
- Cut, mulch, or bulldoze when fruit are not present.
- Minimize disturbance within miles of where this plant occurs, and anticipate wider occupation when plants are present before disturbance.
- Manual pulling and herbicide treatments are hindered by thorny branches.
- Manually pull new seedlings and tree wrench saplings when soil is moist, ensuring removal of all roots and wear eye protection during treatment.
- Burning treatments are suspected of having minimal topkill effect due to absence of litter fuel.
- Readily eaten by goats with potential spread of seed if browsed in spring.
Recommended control procedures
- Thoroughly wet all leaves with Garlon 3A and Garlon 4 as a 2-percent solution (8 ounces per 3-gallon mix). When nontarget damage is not a concern, use Arsenal AC* or Vanquish* as a 1-percent solution in water (4 ounces per 3-gallon mix) with a surfactant.
- For stems too tall for foliar sprays, apply a basal spray of Garlon 4 as a 20-percent solution (5 pints in a 3-gallon mix) or, where safety to surrounding vegetation is not a concern, Stalker* as a 6- to 9-percent solution (1.5 to 2 pints per 3-gallon mix). Mix either solution in a labeled basal oil product, vegetable oil or mineral oil with a penetrant, or fuel oil or diesel fuel (where permitted) (January to February or May to October).
- Cut large stems and immediately treat the stump tops with one of the following herbicides in water with a surfactant: Arsenal AC* as a 5-percent solution (20 ounces per 3-gallon mix) or when safety to surrounding vegetation is desired, a glyphosate herbicide as a 20-percent solution (5 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).
* Nontarget plants may be killed or injured by root uptake.
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