Battling buckthorn trees a rather manageable feat
I just moved into a new home and need to get rid of buckthorn trees that seem to have gotten a foothold in my new garden. What is a good strategy to deal with this pesky weed? — Jessica Alvarez, Highwood
Common buckthorn grows as a shrub or small tree that can reach more than 20 feet in height with a trunk of 10 inches or more in diameter. You probably have a variety of plant sizes to address. This invasive tree is a serious problem that can be found in many home gardens in the Chicago area. Buckthorn tends to hold green leaves late in the fall after the leaves of other trees have turned color or fallen, so is easy to spot at this time of year. Exotic buckthorns are invasive and tend to form dense thickets that crowd out other trees, shrubs and perennials. Many fruits fall below the plants, which creates a dense understory of seedlings. The trees produce lots of fruit that birds eat, thus spreading seeds far from the parent plant. Common buckthorns prefer light shade and are tolerant of many soil conditions, so they grow well in home gardens. Buckthorn was introduced to North America as an ornamental shrub and was selected because of its hardiness and ability to thrive in a variety of soil and light conditions.
The best control measure to use depends on how big the buckthorns are and any adjacent plants that would be damaged by the removal. Smaller plants can be dug up or pulled out. It is easier to pull out seedlings if the ground is moist. A sharp, flat shovel works well to dig out buckthorn. Buckthorn with trunks that are 3 inches in diameter or more will be more difficult to dig out. You will need an ax to cut through larger roots as you dig the stumps out. Digging out large buckthorn may not be feasible if there are desirable trees or shrubs close by or if you have a lot of plants to remove. You may find buckthorn growing in the crowns of shrubs, so look closely as you weed in the garden.
Buckthorn readily resprouts when cut back at ground level at any time of year, so this is not a permanent solution unless you can continue to cut back new sprouts for a few years. The cut stumps should be treated with an herbicide immediately after cutting (preferred) or up to two hours later. Use a triclopyr herbicide (Garlon) or formulation of glyphosate (Roundup) or (Rodeo for wetland areas) to treat the stumps. Brush-B-Gone is a readily available retail product that has triclopyr as an ingredient. Treating stumps works in freezing weather if the proper techniques and herbicide (an oil-based formulation) are used. Be sure to follow label instructions when using any herbicide. This is a good time of year to cut your buckthorns down and treat the stumps with an herbicide. If you prefer not to use an herbicide, cover the stump for one to two years with black plastic to prevent the tree from resprouting. Native habitat managers also use burning to help control buckthorn and other weedy species.
Seeds from buckthorn in the soil can continue to germinate for many years, so monitor your garden and pull buckthorn seedlings as they appear in the coming years. I have been pulling buckthorn seedlings out of my home garden for the last 15 years and anticipate this will be a recurring maintenance task each year, as there are buckthorns in adjacent yards.