Remove dead branches as soon as you see them

QWe have a mature dogwood tree that has dead limbs. When is the best time of the year to trim the dead wood? We also have several oaks that I trim every two years to get the “suckers” off the first 30 feet of trunk. They keep coming back. When should I trim?

AIf you are sure you have dead branches, remove them as soon as you see them. Sometimes trees shed leaves early and you can’t be 100 percent sure what is dead and what is dormant simply by looking. Suckers or sprouts on oak trees can occur if a tree is stressed. It is the tree’s way of trying to grow a new branch. If you don’t want them, cut them when you see them.

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QWe have 27 ligustrum shrubs and two ligustrum trees. They have been afflicted with black spot for a few years now. We have tried Neem oil and hired a professional service to spray these plants to no avail. They keep losing leaves. The shrubs surround our wraparound porch/deck, and they are so thin you can see through them. They range in height from 4 to 6 feet and have spread width-wise to form a hedge. The trees in the front yard have a rounded topiary shape, and they are 10 to 12 feet tall and sculpted to form trees. We cannot afford to replace 27 shrubs and, especially, to replace the two trees as they were quite expensive. Can pruning them down to a height of 3 feet and starting the treatment over help? Also, I have read that if you don’t clean your hedge trimmers, they can re-infect shrubs and potentially spread diseases to other shrubs. Is that true? I read that pouring rubbing alcohol on the trimmer blades can kill the diseases on trimmers.

AI believe your wax leaf ligustrums are suffering from a disease called Cercospera leaf spot. It can be difficult to reverse. For this winter, rake up any leaves that have fallen from the plants and destroy them. In late February, cut your plants back and remove all debris. Keep in mind that rapid new growth can occur with severe pruning, and this new growth can be more susceptible to the disease. Spray with a systemic fungicide such as Fertilome F-Stop, Immunox or Bayer Advanced Disease Control for Roses, Flowers & Shrubs. Follow the spray schedule on the label. You can mechanically transmit the disease from shrub to shrub with your pruners. Cleaning the tool between bushes is helpful, but if you have electric trimmers, use caution with anything liquid. Bleach solutions or alcohol can help on regular pruners. Make sure when you are done trimming that you clean the pruners and lightly oil them before storing, as any bleach solution will cause corrosion over time.

Janet B. Carson is a horticulture specialist for the University of Arkansas Cooperative Extension Service. Write to her at 2301 S. University Ave., Little Rock, Ark. 72204 or email her at jcarson@arkansasonline.com.