by Charlene Burgi
| Crossing limbs in need of pruning
Pruning for fruit production can be confusing. Some trees bear their fruit on new—or “one-year” — wood, while other types require spurs older than three years before they bear fruit. To further complicate this issue, fruiting spurs on some trees only produce for five years while others continue to bear for 15 years. Since pruning can alter the outcome of fruit production, knowledge is key. Let's first look at general training techniques, then focus on procedures for encouraging maximum fruit production.
There are three approaches to shaping a fruit tree. The first method is to encourage a central leader. This creates a shape like a Christmas tree with a strong main stem and multiple smaller side branches, with the larger side branches on the bottom and the smaller branches toward the tip. This type of structure is commonly found in apple, pear, and cherry trees.
|Santa Rosa plum before pruning (top) and after (bottom)
The second training method, called modified leader, is also found in apple, pear, and nut trees. The tree has a strong central leader but—unlike the central leader method described above—here we encourage three to four strong main limbs of equal girth to the central stem. These lateral stems are best located randomly along the main trunk so they are not directly adjacent to each other. This method of training is excellent for controlling the growth of the tree and thus easier for harvesting the fruit.
The last method of training a fruit tree is known as the open center. Peach, nectarine, plum, apricot, and sour cherry trees best benefit from this type of pruning. When the tree is young, remove the central leader and encourage three to four main stems along the trunk to take on a rounded shape. Again, be certain to space the lateral branches along the trunk so none are adjacent to each other. This shape will allow plenty of light into the center of the tree.
When training a tree we’re obviously removing wood, and thus this is where our knowledge becomes critical for production. For example, figs, peaches, nectarines, and persimmons grow on new wood or first-year growth. When pruning these trees you are sacrificing your fruit. (The exceptions are shaping young peach and nectarine trees as described above; and removing crossing, diseased, or broken limbs, which holds true for pruning any tree or shrub.)
Apples, pears, cherries, plums, almonds, apricots, and walnuts form on three-year-old wood. These trees require pruning back two-thirds of the new growth. New spurs will grow on the second-year wood and fruit will form on the three-year-old wood.
All pruning should be done in winter when the sap is down in the tree. Apricots are the exception and are best pruned in July or August to protect the tree from a fungus called Eutypa
(commonly known as gummosis). The fungal spores are easily spread by spring rains and can infect the tree through pruning wounds. Wait until after fruit harvest before pruning. If your tree already shows signs of gummosis (gummy oozing from the wood), cut at least one foot below the diseased wood during the summer months.
I found it interesting that the spurs on different varieties of fruit trees are productive for different numbers of years. For example, walnut tree fruit spurs can be viable for up to 15 years, while most almond fruit spurs are productive for five years. Knowing this, we can encourage new fruit spurs by pruning out old wood in a timely manner, allowing new wood to replenish the old before the tree’s production slows down.
Here's to bumper-crop years ahead!