Weekly Express-News Article

By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist

Saturday, January 26, 2008 

“Pruning Time”

            February is generally the best month to prune most plants. 

 

            Most people think of pruning as a process to control or reduce shape and size.  In addition, pruning is important to maximize usable production of fruit or blooms, and for safety. 

 

            Pruning is time consuming work.  It is generally desirable to select plants that do not require pruning.  This means selecting plants that naturally grow to the size and shape that fills the space rather than trying to fit a square peg in a round hole.  In practical terms it means that a red-tipped photonia should not be planted in front of a window that is four feet from the ground.  It would have to be pruned every year (or more often!) to keep the window open.  A dwarf Burford holly or a dwarf yaupon holly would not have to be pruned in such a situation are better choices.

 

            Many of the plants we use in our landscapes freeze to the roots nearly every year.  They can be pruned to the ground even if some of the stems did not freeze.  This category includes lantanas, esperanza, poinciana, and the blue salvias. 

 

            Modern hybrid tea roses are blooming machines if they are well fed, well watered, protected from pests, and pruned appropriately.  Open up the middle by removing all but three or four stems that arise from the base and angle out at about 60°.  Also remove all damaged, dead, and diseased wood.  It is hard to over prune a modern rose.  They bloom on new wood and grow at a fast rate.  Old-fashioned roses require less pruning.  Just remove old and excessive wood every few years.

 

            Crepe myrtles deserve a special comment.  Like roses they bloom on new wood and many gardeners have gotten used to severely pruning them back each year to leave the infamous “knuckles.”  It is unnecessary and aesthetically offensive to prune the crepe myrtles so severely each year.  The best pruning for crepe myrtles if any is done, is to use a few thinning cuts.  Unpruned healthy crepe myrtles bloom at least as well as the stubbed crepe myrtles. 

 

Fruit trees such as peaches, plums, apples, and pears are pruned to maximize usable fruit each year.  The pruning should open up the middle of the tree for air movement and sunlight.  Pruning also removes a portion of the fruiting wood so that the remaining stems and branches can structurally support the fruit that is eventually produced.  Each species is pruned differently to account for different growth characteristics.  Visit www.plantanswers.com for individual pruning guidance for each species.  The website also has diagrams.

 

            Hedges and conifers are pruned after the first flush of growth in the spring.  For long-term health only one-half of the new growth on each stem should be removed.  Yes, that means that the conifer or hedge becomes a little larger each year until it reaches full size for the species. 

 

            It is also best to wait to prune the early blooming shrubs until after they finish their bloom.  Texas mountain laurel, climbing roses, ornamental fruit trees, and flowering quince are early bloomers. 

 

            Safety pruning is the process of removing threatening plant parts from a plant to protect people or structures from dead branches, rubbing branches, and from branches that reduce vision or free passage on driveways or paths.  The necessity of some of this pruning is obvious but other is not.  A rose branch full of thorns blocking a sidewalk is obviously a problem.  Pecans are notorious for dropping large branches on structures.  The probability can be reduced if a professional arborist prunes the tree every five years to reduce the risk.  Safety pruning should take place when it is needed. Do not wait if the threat to structures or people is imminent. 

 

            Thinning cuts are the most desirable way to achieve size reduction through pruning.  Thinning cuts minimize the disruption to the plants internal hormone system and maintain the natural shape of the plant.   The cuts are made at the point where the offending branch is connected to the next largest branch.  When I say “offending” branch I mean the tallest branch or widest reaching branch.  You cut that branch and the size of the tree or shrub is reduced.

 

            Hedging cuts are easier to make than thinning cuts, but are generally thought of as being less desirable to the plant.  A branch is cut in the length of the branch rather than at its origin in another branch.  Hedging does not maintain the existing shape of the plant being pruned. Some plants tolerate hedging better than other plants.  It is often faster than using thinning cuts because you do not have to make the cuts one branch at a time.