Need a different approach for dealing with large buckthorn

[Conquistador3]

When I was talking about "used", I was talking about a used Stihl pruner gear head/gearbox to bolt onto my existing Stihl trimmer.

You can get a used Echo (whole machine) for the price of a Stihl pruning head. Honestly I prefer Echo/Shindaiwa over Stihl when it comes to trimmers/brushcutters/pruners etc.
I am not a Stihl hater (I have three saws from Waiblingen) but their pricing, used or new, is often borderline silly.

 

[John Lyngdal]

After you make the cut on the Buckthorn, I'd see if your local farm store has Tordon RTU available.
Painting that on stump cut should help kill the roots.