By Rebecca Jepsen
for the Mercury News
January 8, 2010
With winter temperatures hovering near the 60-degree mark, we are all anxious to get outside and unleash some pent-up energy on those unsightly shrubs and trees that took a beating during the recent cold spells.
But directing that energy toward those frostbitten flowers, stems and branches will only leave them vulnerable to more damage by any additional freezing temperatures.
Instead, focus your activities on winter pruning that will provide bushels of benefits in the months and years to come. Now is the time to prune many varieties of fruit trees, roses and shrubs.
The best time to trim most fruit trees is when they are dormant (their leaves have dropped off). It is much easier to see what you are doing and, unlike summer pruning, winter pruning is done to invigorate growth.
Young trees need to be pruned to encourage growth and branching that will make them structurally sound, easy to care for and highly productive.
Winter pruning of mature trees increases fruit size and quality and opens up the canopy to accommodate spraying, thinning and harvesting.
Nancy Garrison, the founder of Santa Clara County's Master Gardener organization, recently held a winter fruit tree pruning workshop for AmeriCorps members at Full Circle Farm in Sunnyvale. Garrison, who started the local program in 1982, is an expert on selecting, planting and pruning fruit trees that do especially well here in Silicon Valley.
First and foremost, you will want to gather the proper tools. You will need a pair of hand clippers for branches up to three-fourths of an inch; loppers work well for branches from three-fourths to one inch; and for anything larger, it's best to use a pruning saw. Be sure to clean your tools before you begin; otherwise you can introduce disease and infection through the fresh cuts you will be making. Garrison recommends using Scrubbing Bubbles; spray all cutting edges, use a metal brush to scrub, rinse with water and wipe down with a clean rag.
Shaping the trees
Apple and pear trees are characterized as central leader trees. They have one main, upright trunk. Branching usually begins on the leader at 18 to 24 inches above the surface of the soil. During the first year, the tree is trimmed to create three to four branches that are uniformly spaced around the trunk; this is called a scaffold whorl. As the tree grows you want to leave an open space of 18 to 24 inches between whorls in order to allow light into the center of the tree. Subsequent pruning should create multiple tiers of whorls up to the desired height of the tree.
A properly trimmed central leader tree will resemble a Christmas tree. Branches will be wider at the bottom and progressively shorter toward the tallest point — this will allow maximum light penetration and airflow throughout the entire tree.
Cherry and stone fruit trees (peaches, plums, nectarines and apricot) prefer a more open-centered, wineglass shape.
Where, what to prune
Now to the pruning. The first plan of attack is to remove all diseased, damaged and disfigured branches. Next you want to remove all crossing branches. Removing all competing branches (branches that are too close, off the same fork or growing in the same direction as each other) will allow proper spacing for fruit growth. You want to remove all suckers (branches growing from the base of the tree), water sprouts (thin, vigorous branches that grow straight up) and all other branches that have a "weird" and/or unsightly growth pattern.
Don't remove short, stubby branches that grow on horizontal limbs; these are the fruit bearing shoots called spurs.
The final cuts
Lastly, you want to perform tipping cuts to most of the remaining horizontal branches. Tipping is done to renew fruiting wood and thin excessive buds. You want to make your cuts just above a bud that is "pointing" in the direction of where you want the branch to grow.
You need to be somewhat ruthless and apply a bit of tough love to ensure that you are removing everything that needs to go.
Although it may seem severe, proper pruning will provide a strong and healthy structure for your tree. It will help prevent disease and will boost the overall health of the tree by providing good airflow and necessary light penetration.
Although based on lots of scientific data, there really is quite a lot of "art" involved with successful pruning. It allows you to "paint" the future shape of your tree, so take your time, step back to assess your "subject" frequently and enjoy your canvas.
Rebecca Jepsen is a Master Gardener and executive director of Full Circle Farm. Veteran Master Gardener Nancy Garrison contributed to this column.
Have a question for the Master Gardeners? Call the Master Gardener hot line, 408-282-3105, from 9:30 a.m. to 12:30 p.m. Mondays through Fridays.
PRUNING WORKSHOPS, RESOURCES
If you want to really learn the art of pruning, it is highly recommended that you attend a hands-on workshop. The Master Gardeners, a University of California Cooperative Extension volunteer organization dedicated to providing research-based gardening information to home gardeners, is offering several fruit tree workshops this month, including one on grafting at 11 a.m. today at Emma Prusch Farm Park in San Jose. Find more events on www.mastergardeners.org/events.
If you are going to purchase just one reference book on fruit tree pruning, Nancy Garrison recommends "How to Prune Fruit Trees" by R. Sanford Martin.