News

woman from the city service has been health pruning the trees with the help of professional clippers

By Harry Brook

It may feel like the wrong season for it, but now is an ideal time to be pruning those trees you’ve been thinking about. The best time for pruning a tree is when it is dormant. Pruning in late fall or early winter can result in some new growth if there is an unseasonable warm spell.

Winter pruning is the best time because it is easier to see dead or diseased branches. You don’t have to worry about sap bleeding and spreading a disease. Also, winter pruning stimulates new growth first thing in the spring.

tree pruning column copyWhy prune? We prune trees to improve the health and the shape of the tree. You want to allow good air circulation and light penetration into the tree. That maximizes photosynthetic sun capture and prevents possible disease spread. Trees with branches growing laterally are more likely to be damaged if there is a heavy load placed upon it. This could be due to an extra heavy fruit crop or early spring heavy snow. Those branches weaken the tree and may encourage disease by cracking open the bark.

There are four main types of pruning. They are crown thinning, crown raising, crown reduction and crown cleaning. The reason the crown is involved in all of them is that the crown is where most of the photosynthetic activity occurs.

Crown thinning involves removal of selected live branches to reduce the density of branches in the tree to increase sunlight penetration and air flow. Thinning takes only 10 to 20% of branches and shouldn’t change the shape or size of the tree. It should not even look pruned. Crown raising is a gradual removal of lower branches, over time, to improve access under the tree or sightlines. Crown reduction is usually used on older, more mature trees. It can help strengthen the tree and encourage new growth. Branches are cut back to the growing lateral branch. Finally, crown cleaning removes dead or diseased branches. This can be done at anytime versus the other three trimming methods.

You can trim healthy branches during the growing season but you risk weakening the tree. After it puts energy into growing new shoots, trimming them is counter-productive and that energy has been wasted. When pruning is done in winter, there may be some bleeding of sap in the spring, but it will quickly stop with the onset of new growth.

The right tools for the job make it so much easier. Hand secateurs are useful cutting stems up to a half-inch in diameter. Loppers have long handles for added leverage to cut branches one to two inches in diameter. Anything bigger, use a pruning saw, which can cut through a branch quickly with aggressive teeth. When using a saw, cut off the branch twice to prevent damaging the tree. Cut branches at the node, where one branch attaches to another.


Harry Brook is Flagstaff County's Agricultural Fieldman. He can be reached via email at: This email address is being protected from spambots. You need JavaScript enabled to view it. or by phone at: 780-384-4138.