I have 7 pistachio trees in my garden in Aegina, Greece. Three of them, the youngest trees, seem to be growing out from the base (root) of the tree, which I cut every year. What is this problem? The other trees are perfect.
Certified GKH Gardening Expert
It's possible the tree is sending up shoots from the root stock if the tree is grafted.
Remove those sucker shoots.
Here is a link with good information on pruning.