Buckthorn is evil. Cutting it will just make it mad, pulling it out by the roots is exhausting and could cause soil erosion issues, and yelling obscenities at it has proven less than effective.
This is the approach I took 2 years ago to reclaim about an acre of pasture area. After 2 summers, the buckthorn hasn’t grown back, the remaining stumps have rotted to the ground, and the critters are grazing on the tall grass.
Step 1: Cut down the Buckthorn
I use a Stihl FS90 Bike Handle Trimmer with a forestry blade attached. This lets me slice right through the small diameter of the buckthorn. As long as the diameter is less than 2″, the Stihl will zip right through it.
Cut it about 6″-10″ above the ground so you can clearly see the stumps. You’ll understand why in the next step.
STEP 2: Treat the Buckthorn Stump
The next step is to apply a 2 4-D weed killer to the stump. I use Gordon’s LV400, add a little food coloring to it, and apply it with a small brush. The food coloring is so you can see which stumps you’ve already treated.
After a month or two, once I’m sure it is truly dead, I’ll come back and cut the stump as close to the ground as I can with the Stihl FS90.
STEP 3: The Satisfying Part
Now, you may be wondering what to do with all of the buckthorn you just cut down. Well…
One last thing…
During the warmer months of May, June and July, the sap in the buckthorn is running upward from the root. So, these are not good months to use this technique as the LV400 will not get sucked down into the root and kill it. I prefer to cut and treat during a warmer stretch of winter days where the temperature is above freezing.