- Smooth buckthorn is a member of the Buckthorn family (Rhamnaceae).
- Smooth buckthorn is a rangy, deciduous shrub or small tree growing 6-23 feet tall. The species is most easily identifiable by its thorn-less branches and stems, which are covered by fine, wooly brown hairs. Conspicuous black round fruits ripen in late summer through early fall.
Leaves are alternately arranged, simple, one to three inches long, and dark green and shiny from above. (5)
Flowers have five white to yellowish green sepals and are arranged in clusters of two to eight flowers in the axils of the leaves on the plant’s new growth. Flowers are perfect, with both male and female parts present. (4)
Smooth buckthorn fruits are fleshy, round and approximately ¼ inch in diameter. Fruits turn from green to red to black throughout the course of summer into fall and are found in clusters close to the stem. (4)
A single mature individual of smooth buckthorn is capable of producing over 1,500 seeds a season. Studies suggest the species’ reproductive potential may be lower on less fertile, dry sites, however. Seeds are also predated on by rodents, destroying the embryo and reducing the species’ seed bank. Studies suggest seeds may remain viable in the seed bank for approximately 2-4 years. (6) Vectors include birds, small mammals, water and horticultural trade. (3)
There is currently no single optimal biological control agent in use against this species. (3)
Manual or Mechanical Control
Pulling / Digging Up Pulling by hand or via a weed wrench is an effective method of control for seedlings and smaller plants.
Mowing: Regular mowing, particularly in open areas will reduce or halt fruiting. Successive cuttings, at least 2 for at least 3 years, will reduce the size and density of common buckthorn infestations but will likely not eradicate it. (8)
Girdling: Larger stems may be girdled and re-sprouts clipped or sprayed as they emerge. (8)
Prescribed Fire: Fire will top kill the species and re-sprouting will occur. (7)
Prescribed Grazing: Smooth buckthorn may be browsed by deer, particularly in open environments, however, it is not a preferred species. The species is poisonous to some livestock, such as horses and cattle. (3)
Soil Tilling: Not advisable. Tiling will fragment roots and encourage re-sprouting. It will also expose more seeds for germination. (8)
Mulching: Not applicable
Solarization: Not applicable
Hot Foam Spray: Not applicable
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.
Foliar Spray: A 2-3% solution of glyphosate or triclopyr is effective at managing small plants of smooth buckthorn, although repeat applications may be necessary. Infestations managed in this way should be revisited in 2-3 weeks to monitor for regrowth. Always read and follow all instructions on the herbicide label. (8)
Cut Stump: A 50% solution of glyphosate or triclopyr is effective at managing larger plants when applied in the late summer or fall. Studies suggest that root sprouting can occur two to three years after treatment: subsequent follow up management must be scheduled at this time. (7)
Basal Bark: A 30% solution of triclopyr in oil is effective on smaller shrubs (i.e. less than 6 inches in diameter) when applied between midsummer and December.(8)
Stem Injection: Not applicable
Pre-Emergent Spray: Not applicable
General management overview and recommendation
As with any other invasive infestation complex, large stands of smooth buckthorn are best managed via a combination of mechanical and chemical means. Small seedlings and plants can be hand pulled or removed using a weed wrench while larger shrubs must be cut and sprayed, either with a basal bark or cut stump application, to attain good control. All managed infestations should be monitored to ensure exhaustion of the seed bank for at least two years and to prevent reinvasion from nearby populations. Any new seedlings can be hand pulled or sprayed.
Post treatment monitoring
Any infestations managed by chemical means must be revisited in 2-3 weeks to check for treatment efficacy, unless the application occurred during dormancy, in which case, follow-up during the growing season will be necessary. Infestations managed solely by mechanical or physical means will need consistent follow up treatment to manage root suckers and sprouts. Due to the long-distance dispersal mechanisms of smooth buckthorn, managed infestations must be checked for reinvasion.
Waste material can be burned, chipped or composted so long as management was completed prior to seed set. Any fruit must be bagged and disposed of. All roots must be thoroughly dried and or crushed.