Buckthorn, Common

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Identification

Appearance

Common buckthorn is a deciduous shrub or small tree that can grow to 25 feet in height. The bark is dark gray and the inner bark is orange (easily seen when the tree is cut). Twigs are usually tipped with a sharp spine.

Foliage

The leaf arrangement is usually subopposite, but examples of opposite and/or alternate arrangements are commonly found. Leaves are dark green, oval, 1.5 to 3 inches long, slightly serrate with 3 to 4 pairs of curving veins and a somewhat folded tip.

Flowers

Flowering occurs in the spring, when yellow-green, 4-petaled flowers develop in clusters of 2 to 6 near the base of the petioles. Plants are dioecious (male and female flowers occur on separate plants).

Fruits

Fruits are small, black berries that are 0.25 inches in diameter.

Check out the downloadable fact sheet above.

Check out this video by RiverBankMedia on identifying buckthorn.

Biology

Ecological Threat

Birds and mammals feed on buckthorn berries during the winter, aiding in the dispersal of seeds. While buckthorn may benefit from this behavior, the feeding animals do not. Buckthorn berries contain emodin, a natural laxative, that prevents mammals from digesting sugars found in the berries.
Like many other invasive trees and shrubs, buckthorn leafs out early and retains its leaves into late fall, giving it a much longer advantageous growing season than native plants.
Buckthorn can increase the amount of nitrogen in the soil, impacting the composition of native species that can grow in the area.
Common buckthorn invades forests and can form dense thickets crowding out native shrubs and understory plants. Once established, it is difficult to remove.

Origin

Common buckthorn is a native of Europe and was introduced into the United States as an ornamental shrub

Habitat

Forests, forest edges, meadows, fields, disturbed areas

Life Cycle

Buckthorns reproduce by seed but plants can root sprout or regenerate even after they are cut or burned. Plants mature at 5-6 years old. Seed production is prolific. Common buckthorn fruits ripen from August to September while glossy buckthorn fruits ripen earlier—July to August. Seed germination rates are high and germinate well in the shade. Seeds remain viable for at least 2 years. Plants are usually dioecious; males do not produce fruit. Fruits are eaten by birds, mice, and deer. Seeds viable for 2-6 years.

Management Options

This species is Quarantined: Class B Noxious Weed

Treatment concerns:

Common buckthorn typically "leafs out" early and retains its leaves into late fall, making it easy to detect in spring and autumn.
Because of the high risk of spread by seeds, treatments are most effective before the plants go to seed.
The species is dioecious (separate male/female plants). With the main vector of spread being seeds, it is prudent to prioritize treating fruit producing plants first.
If feasible and fruit is present, bag and dispose of fruits to prevent seed dispersal during management activities.
Follow-up treatments will be needed for at least 5 years because of the seed bank.
Any removed plants are best left on site in a manner to allow roots to dry out and decompose.

General guidance:

Most methodologies alone will not suffice and should be part of an integrated pest management plan.
Which methods you choose also depend on the purpose of control: eradication (removal of all plants, plant parts, and seed bank), or containment (reducing seed production, reducing spread, reducing growth, removing individual plants near site of concern).
All action promotes disturbance - mechanical, chemical, and even just doing nothing. Our work is in figuring out how to minimize disturbance and maximize positive benefits.
The intent of mechanical or chemical treatment is to kill target plants.
Management options listed below are representative of research by institutions like The Nature Conservancy, Michigan Department of Natural Resources, and New York Invasive Species Information
Here are additional guidance documents on best management practices for common buckthorn.
New York Invasive Species Information Profile on Common Buckthorn
Michigan Department of Natural Resources Best Control Practices for Common Buckthorn

Summary of Mechanical Treatment Options

Mechanical treatment can sometimes cause greater disturbance than if the site was left alone or if another treatment option was utilized.
If pulling or digging, remember that soil disturbance can encourage growth from seed bank.
This species resprouts vigorously from roots or stumps not fully removed.

text in a table describing mechanical treatments for Common Buckthorn

Summary of Chemical Treatment Options

Be careful not to damage or kill nearby desirable plants when conducting management work.
Always read and follow pesticide label directions. Application of pesticides may require a certification from the Agency of Agriculture, Food and Markets. The Agency website provides information on what applicator certification is needed.
If a treatment for a specific species isn’t listed on a given product, don’t use it.
Product labels may require you to check Endangered Species Protection Bulletins. Learn more about protection bulletins here.
Understand the risk of, and how to avoid, drift.
The timing of some chemical treatments may overlap with when certain plants are flowering, and, in order to protect pollinators, herbicides should not be applied when plants are flowering. To mitigate the risk, consider utilizing an integrated pest management plan, such as cutting the plants to set back flowering time, and then applying pesticides in the lowest effective volume.
Chemical treatments pose a risk to plants, animals, and humans, but can be used in ways that greatly reduce this risk, and provide a solution to otherwise hopeless scenarios.
For questions regarding the appropriate chemical to use for a particular situation, or general information on pesticide safety, ingredients, and more, contact the Vermont Agency of Agriculture, Food & Markets’ Pesticide Program.
For questions about certification and continuing education credit opportunities, contact the Vermont Agency of Agriculture, Food & Markets’ Pesticide Program.
For questions about additional training opportunities, contact the UVM Extension Pesticide Safety Education Program.
Special permits are required to apply herbicides in a wetland. Contact Vermont Department of Environmental Conservation’s Wetlands Section for more information.
Herbicides cannot be applied within 200 feet of a Public Water Source Protection Area unless the Water Supply Division is notified. Call 1-800-823-6500 for more information. Similar requirements may be in place for proximity to private water sources.
Forests that are certified organic or adjacent to organically certified agricultural lands may carry restrictions regarding chemical application. Check with the Northeast Organic Farming Agency of Vermont for more information.
The National Pesticide Information Center provides objective, science-based information about pesticides. Check out their website for more information or call 1-800-858-7378.