Question:
On my young shade tree, two branches suddenly zoomed up that are taller than the rest. Should I cut them back to the same height as the others?
Answer: Your tree has produced two leaders. Generally shade trees should have one dominant leader branch which is taller and stronger than all others. You want to encourage this leader to direct growth upwards. Choose your straightest, most vigorous, and best-positioned leader to retain. Prune the competing leader several inches shorter, so it does not out grow the leader. See page 5 of our online publication, Pruning Ornamental Plants.
Question: My lilacs' leaves are about 1/10 normal size and didn't flower. They are 10 years old, in full sun, with good drainage. I see holes in the bigger stems.
Answer: Lilac borer is the larvae of a clearwing moth which resembles a wasp. This larvae tunnels in lilac trunks, pushing out sawdust-like frass and cracking bark. Prune dead and dying trunks to the ground - or at least well below the tunneling - and destroy them. Older trunks are what borers attack. The best prevention is renovation pruning: i.e. every couple of years cut out large old trunks. Keep mulch away from the base of the lilac. Water during droughts and avoid wounding with lawn mowers and string trimmers. For bad infestations, spray permethrin on trunks in mid April as a preventative.