Mastic Tree Problems

Q. Can you tell from the attached pictures what might be happening to our mastic tree?

Mastic tree.

A. My guess is that the new growth is filling a “hole” made when the plant became a shrub. Mastic is a Mediterranean tree or shrub that grows slowly and naturally as a bush, to about 20 tall by 20 feet width. It requires, at the least, annual pruning when it is young to shape it into a single or multitrunked tree. It is best used as a background tree or shrub and not a smaller version of the larger Chinese pistache. It is not as pretty. It lacks fall color, tends to be shrubby, and smaller, but does have red ornamental nuts when they are young and before they ripen around August.

            If this plant were mine and I wanted a small tree instead of being shrubby, as it tends to be, I would start to prune it in the winter or late fall months. Make a decision whether you want it as a single or multi trunk tree and make the appropriate cuts.  I would expose the trunk or trunks of this tree up to my knees by starting at the bottom of the tree. I would eliminate any growth below my knees and keep any upright growth. If I saw any suckers at the base, I would eliminate them. While it’s young, I would eliminate any growth growing downward or horizontal. I would concentrate most of my pruning efforts on keeping any upright growth to make it look like a tree and give it some height.

            Water it like you would an olive tree. It is mesic in its water use. It will attract the leaf footed plant bug. Shearing this tree with hedge trimmer is a mistake. Fertilize this tree once or maybe twice lightly with a standard landscape fertilizer such as 16-16-16.