January and February are busy months for area fruit growers who learn techniques and share ideas at their monthly California Rare Fruit Growers meetings.
The group, a chapter of the statewide organization, held its annual pruning workshop Jan. 11, and will host its biggest event, the popular Scion Exchange, on Feb. 15 at Cal Poly.
The January workshop, Pruning Deciduous Fruit Trees, featured Tom Del Hotal, nurseryman, arborist and educator from San Diego. Del Hotal was chosen for his unique approach to pruning, which is mainly to use the same standards applied to landscape and street trees for fruit trees, based on research by Richard Harris and Alex Shigo.
“All trees bear fruit, it’s just that some are edible and some are not, so why do we separate fruit trees from the International Society of Arboriculture standards?” Del Hotel said.
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The main difference in Del Hotal’s method and traditional methods is the concept of “drop-crotch” pruning, which means the cutting back of limbs to their point of origin or to a lateral branch that will assume dominance.
“This method of crown reduction is not the same as topping, which creates many large wounds and can shorten the life of the tree,” explains Del Hotal.
Rather than just concentrating on fruit production, Del Hotal stressed the importance of pruning for the tree’s structural strength. This includes training the scaffold branches to be spaced vertically and radially when trees are young.
He stressed the removal of co-dominant leaders, or branches, which arise from the same point on the stem, leaving just one. Crotch angles of branches should be between 45 and 90 degrees, as lower angles develop poor attachment and can easily break off under the weight of fruit.
“For a healthy tree, prune off the four Ds — dead, damaged, diseased and dysfunctional branches,” Del Hotal said.
A dysfunctional branch is one that crosses or touches another limb, blocks light or is heading in the wrong direction. He stressed not leaving branch stubs, which can encourage insects and prevent healing. Correct cuts should be flush with the top of the shoulder, the swollen area at the base of the branch, as this is an area of quick healing.
One of Del Hotal’s more novel concepts is the idea of training branches on a young tree, using any 1-inch material to tie the branch to a stake. This is preferred over pruning of a new tree. Training enables the grower to redirect the branch outward, to a wide crotch angle or to open up a bowl shape. He uses any material, cloth, old nylons or rubber inner tubes.
The strong scaffold structure is established while the tree is young, helped by maintaining single dominant leader growing upward.
“This leader should not be pruned back, and don’t let secondary branches outgrow the leader,” del Hotal says. The reason is that codominant stems lead to structural weakness.
After the outdoor classroom presentation, Del Ho tal and the group of 150 students of all ages headed for the California Rare Fruit Growers orchard on the Cal Poly campus.
There, he demonstrated the steps of pruning: removing suckers, opening up the center as a vase or bowl for light, but leaving some of the branches facing inward for shade and fruit production, then working each scaffold (main) branch one at a time, starting at the base. Different fruit trees have varying needs, so it’s important to know the fruiting habits of your particular tree.
“Pruning is like playing chess, as you develop a strategy for the future, leaving some vegetative or temporary branches for increased root health, with a plan to remove them the next year,” he said.
He stressed the importance of not removing all of the inner branches along main trunks, but to space them so they grow spirally around the truck with distance between each.
“Traditional pruning practices cause the shortlived nature of fruit trees. I’m unique in that I believe better pruning techniques can give us longer-lived, healthier trees. If I can leave as a legacy better ways to prune fruit trees, then I’ve done something good,” Del Hotal said.
For more lectures and information from Tom Del Hotal, go to: http://crfgsandiego.org. To view a YouTube lecture on winter pruning: http://www.youtube.com/playlist?list=PLVp-xu9ZgVVEb8.
ANNUAL SCION EXCHANGE AND GRAFTING CLINIC
Purpose: To teach how to graft scions (small fruiting branches) onto an existing fruit tree and take home scions of hundreds of varieties of fruit to graft. Grafting technique demonstrations by experienced California Rare Fruit Growers members will also be given.
Cost: Free, open to the public; parking is also free
When: 1:30 p.m. to about 3:30 p.m. Feb. 15
Where: Cal Poly Crops Unit, Building 17, Cal Poly campus. It’s on the left at the corner of Highland Avenue and Mt. Bishop Road. Enter the campus off of Santa Rosa.
What to bring: If you have recently pruned your fruit tree, bring a pencilsize scion to exchange in a plastic bag with a moistened paper towel. Be sure to put the name of the variety on the bag.
For sale: Grafting supplies, as well as rootstock to start your own fruit tree.
For more information: http://www.crfg-central.org