I have three Chinese Pistache and want to know if I can trim the tops. They are about 18 ft tall now at the age of five, growing straight up, not rounding out. They are very healthy, and I wouldn't want to injure or kill them. Thanks.
Certified GKH Gardening Expert
I would leave them alone for now. These trees get much taller when mature and will branch out at they get bigger. If you nip the terminal bud now, the trunks will split.