Common buckthorn (Illegal to sell in Illinois)

Common buckthorn is an invasive plant in Illinois and should not be planted. It forms dense thickets and reproduces very freely, crowding out other plants and disrupting ecosystems in forest preserves and other natural areas. In woodlands, it can completely replace existing understory plants, including native wildflowers. Buckthorn has berries that are spread by birds. The seeds germinate at a very high rate and remain viable in soil for two to three years. Buckthorn is very common in gardens and yards in the Midwest, but should be removed where it is found. Buckthorn is a large shrub or tall tree with glossy oval leaves that can easily be recognized in fall, when it remains green after most other leaves have fallen. The Illinois Exotic Weed Act prohibits the sale of buckthorn in Illinois.

Family (English) Buckthorn
Family (botanic) Rhamnaceae
Tree or plant type Tree, Shrub
Foliage Deciduous (seasonally loses leaves)
Native locale Non-native
Size range Large shrub (more than 8 feet), Compact tree (10-15 feet), Small tree (15-25 feet)
Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily), Full shade (4 hrs or less of light daily)
Hardiness zones Zone 3, Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7
Soil preference Acid soil, Alkaline soil, Dry soil, Moist, well-drained soil, Wet soil
Tolerances Alkaline soil, Dry sites, Road salt, Wet sites
Flower color and fragrance Inconspicuous, Orange
Shape or form Multi-stemmed, Round
Growth rate Fast, Moderate

Native geographic location and habitat:

Native to Europe

Bark color and texture:

The bark is brown to gray in youth. Rough and peeling, the stems have prominent whitish lenticels and the interior wood is yellow. The stems may form dense thickets.

Leaf or needle arrangement, size, shape, and texture:

Leaves are opposite to sub-opposite, 1 ½ to 3” long, and ¾ to 1 ½” wide. They are elliptical in shape with minute teeth on margins and rounded to pointed tips. Leaves remain bright green in fall for some weeks after most other shrubs and trees have lost their leaves.

Flower arrangement, shape, and size:

Male and female flowers are on separate plants (dioecious). The flowers are small, green and fairly inconspicuous.

Fruit, cone, nut, and seed descriptions:

Berry-like fruits are borne in clusters on female plants only. They are dark blue in late spring and early summer, turn black in August and persist throughout the winter.

Plant care:

This is an invasive plant. It is illegal to sell in Illinois.

However, if the plant is already persisting, there are several management methods. Buckthorn can be managed culturally by pulling small plants and seedlings or mowing them over. Large plants can be girdled by removing 2 inch strips of bark from each stem and applying herbicide to the girdled surface. Buckthorn can also be controlled chemically in late fall. Systemic chemicals can be sprayed on the plant to be drawn down into the plant’s roots. A stump treatment can be implemented by spraying or painting glyphosate or triclopyr on a freshly cut stump.

List of pests, diseases, and tolerances:

Buckthorn is susceptible to rust and powdery mildew.

Buckthorn is on Illinois’ exotic weed list due to its high germination rate in a variety of habitats including gardens, fence rows, pastures, prairies, and abandoned farm fields. In woodlands it can completely replace existing understory plants, including native wildflowers. Seeds remain viable in soil for 2 to 3 years which contributes to the invasive nature of this plant.