Jan. 04--I just bought my first house and the neighbors have told me that I have a lot of buckthorn that needs to be removed. Can I do that over winter to get a jump on spring, when I will be busy doing other things?
-- Brenda Larson, Evanston
Common buckthorn is a widespread weed in northern Illinois gardens and an aggressive invader in natural areas. It tends to hold green leaves late in the fall after other trees have turned color or fallen. Exotic buckthorns are invasive and tend to form dense thickets that crowd out other trees, shrubs and perennials and pose a serious threat to natural areas; they are a big nuisance in gardens. They will spring up in the bases of shrubs and along lot lines and can take over sections of a garden over time. Many fruits fall below the plants, creating a dense understory of seedlings in garden beds. The trees produce lots of fruit that birds eat, thus spreading seeds far from the parent plant.
The buckthorn growing in your garden may also be causing problems in any natural areas near your home. Common buckthorn prefers light shade and is tolerant of many soil conditions. It was introduced to North America as an ornamental shrub and selected because of its hardiness and ability to thrive in a variety of soil and light conditions.
Winter is a good time to remove buckthorn. Loppers and handsaws work well to cut back small- to medium-size plants; a chain saw will be required to cut large buckthorn.
It is best to wait until the ground is frozen to minimize damage to existing good plants. Working in natural areas when conditions are wet like they currently are can cause lots of damage. The best control measure to use will depend on how big the buckthorns are and any adjacent plants that would be affected by the removal.
Buckthorn will readily resprout when cut back at ground level and not treated, so this will not be a permanent solution unless you can continue to cut back new sprouts for a few years. The cut stumps should be promptly treated with an herbicide after cutting for good results. The stumps of large buckthorn can also be ground with a machine, providing there is access. Use a triclopyr herbicide (Garlon) or formulation of glyphosate (Roundup or, for wetland areas, Rodeo) to treat the stumps. "Brush B Gon" is a readily available retail product that has triclopyr as an ingredient. Treating stumps will work in winter if the proper techniques and herbicide are used. Be sure to follow label instructions when using any herbicide.
Tim Johnson is senior director of horticulture for the Chicago Botanic Garden in Glencoe.
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