Pruning Trees and Shrubs
By Ron Gatewood

Why periodic pruning is needed:

Pruning is necessary for controlling size and shape, crossing branches, flowering and fruit development. It also removes dead, diseased, weak, or broken limbs, and can be used to stimulate new growth. A neglected, overgrown plant can develop into something that is hard to correct, so start the process before they reach mature size. Young trees need pruning to correct growth anomalies. Start training them early in life and you will reduce the need for large pruning wounds later.

When should you prune?

Dead, diseased, or damaged limbs should be removed as soon as possible. This will reduce the spread of decay, disease, and reduce potential safety hazards. When pruning healthy plants, it’s important to know what type of plant you have and how it will respond before you start. Spring flowering shrubs and trees form flowers on the previous season’s growth and should be pruned after blooming. Summer and fall blooming plants form flowers on new or current growth, so they should be pruned in either late winter or early spring before the new leaves emerge. Non-flowering shrubs may be shaped in the summer prior to August 15th. This will give the shrub time to harden off the new growth prior to the onset of freezing weather.

Prune azaleas and rhododendron by pinching back the growing tips to a healthy bud, after the flower petals fall off.

Yews, juniper, and arborvitae can be pruned by shearing or heading back by cutting part of the new growth off in the summer time.

Pines, spruce, fir, hemlock, and other needled trees may be pruned sparingly by pruning half of the candle or new growth back just prior to its full development, usually in June for our area. However, these plants are more pleasing when left unsheared, and it’s recommended that you avoid pruning them if at all possible.

Hollies are typically sheared or headed back in November and December, although I’ve had no problems with pruning them in the summer.

Hedges are sheared in the summer time for shape, making sure that you always make the bottom of the shrub wider than the top.

Deciduous trees are typically pruned in the dormant season when the leaves are off. This makes it easier to see growth anomalies and correct the shape or growth habit. Sap feeding insects are overwintering and therefore less likely to expose your pruning wounds to the pathogens they may carry. Try to avoid pruning ash, maple, birch, elm, and dogwood from February through April. They have excessive sap pressure and will bleed if pruned during those times. Avoid pruning oaks from April 1st to September 1st. They are especially susceptible to disease pathogens spread by sap feeding insects.


Pruning techniques:

Thinning – this technique is used when the outside of a shrub or hedge is getting so thick that light isn’t penetrating into the canopy and you develop an inside dead zone. Go into the interior and remove a few branches back to the main stem to allow light to penetrate the dense canopy. Make your cut back to an outward facing bud or crotch angle on a branch.

Rejuvenation – this method removes all growth back to 4” - 6” above the ground, forcing new shoots to emerge from the crown. This is suitable only on certain plants. It’s always best to check with a professional prior to making the cuts, to see if the plant will respond to this technique.

Shearing – this technique removes a portion of the current season’s growth and can be utilized one or more times per year. This gives the shrub a formal appearance, but concentrates the foliage to the perimeter of the plant. Once you start using this technique, it will be hard to go back to any other form of pruning without changing the aesthetics of the plant.

Heading - this is better for your plants though more time consuming. You can still maintain somewhat of a formal appearance while making your cuts just above an outward facing bud on the stem you are pruning.

Renewal pruning – this technique is used in the spring on large multi-stemmed shrubs by removing a few of the older stems back to the crown. New growth is stimulated, encouraging flowering and fruiting, while promoting light and air flow for good plant health.

Tree pruning: – Make all cuts just outside of the branch bark collar to promote wound closure. The only stub allowed is a good branch bark collar. Reduce the length of a branch by pruning back to a crotch or just above a bud. Avoid indiscriminately cutting the branch and leaving a stub. Make a good cut in the correct location to promote tree health. This is why tree topping is bad. The wounds are too large and incorrectly located, promoting poor tree health and reducing its life span. Remove suckers from the base of the stem and water sprouts from the tree canopy to promote tree growth and proper canopy development. After making your pruning cut, let nature take its course, using nothing on the wound to cover it.

Pruning trees and shrubs correctly takes practice and a little bravery at first. Eventually it becomes fun and creative, and your plants will certainly benefit from the use of these pruning techniques.