Response of buckthorn to basal bark herbicide treatment

If you have been following this blog, you know that I am a big fan of herbicide treatment of woody plants by the basal bark method with Garlon 4. This has the advantage that one confines the herbicide to just the target species. Carried out properly, there is no need to slop herbicide all over the ground.

Last fall we used basal bark treatment on lots of small buckthorn plants. We are now seeing the results of our work.

The photo shows a buckthorn plant whose leaves are just coming out. You might at first think that the herbicide was not working, but if you look carefully you will see that these leaves are curled in "funny" ways. They aren't healthy leaves. Likely in a few days they will curl up and die.

I have never seen any research on this phenomenon, but my explanation is that the herbicide that was taken in last fall by our treatment sat all winter in the roots. Now that temperatures are warming, plant metabolism is starting, and the herbicide is able to exert its action. The leaf buds at the top of the shrub were able to get started "before" the roots were affected, but this was just a temporary phenomenon.

The same phenomenon can be seen in large buckthorn plants that have been basal barked. Here the leaves may come out and even look normal, but sometime around the end of May or early June they curl up and die. Although the whole buckthorn plant dies, it may remain intact for a year or two. Eventually, its roots rot off and the plant falls over. If you walk through an area where buckthorn plants had been basal barked in a past year, you should be able to simply push the whole plant over, or even pull it up by the roots.