We are fortunate that leaves on fruit and shade trees dropped later than usual last fall, virtually eliminating the possibility of November pruning. If trees had been pruned, we would be looking at extensive dieback this April as a result of the bitter cold in January and February. With the worst of winter behind us and moderating temperatures likely, inspect your trees now to see if pruning is required. If it is, prune this weekend or next week.
Not all trees will need pruning. If your shade trees are healthy and aren't a danger to pedestrians or the house, leave well enough alone. Focus instead on keeping the trees growing vigorously. You'll be feeding your trees next week as part of that commitment.
Fruit-bearing trees have their own ground rules. If you're not interested in eating fruit from the tree, it's unlikely that pruning is needed. You may want to thin out some of the pencil-thin limbs that have sprouted, but no major cutting is necessary. However, if you want to eat fruit from the tree in the foreseeable future, pruning is essential. Normally, prune every three years for optimum fruit production.
Fruit trees that are candidates for pruning now are apple, cherry, crab apple, nectarine, pear, peach, plum and quince. Apricot trees are not winter hardy and should not be pruned until late April.
Some shade trees that are candidates for pruning now include ash, aspen, beech, catalpa, cedar, elm, hackberry, hawthorn, hemlock, hickory, honey locust, linden, locust, magnolia, maple (except Japanese and sugar maple), mountain ash, oak, poplar, sweet gum, walnut and willow. Evergreens (fir, pine and spruce) may also be pruned now, but postpone "shearing" them.
Shade tree pruning is usually dictated by structure. If the tree is healthy and growing vigorously each year, little pruning is needed except to remove cracked or dead limbs. Branches that threaten to poke your eye out should be removed, too. Beyond this, leave well enough alone, but make sure you feed the trees in the coming weeks. Next week's column will focus on tree fertilization.
While pruning can be as complex as you make it, the rules are simple. Very low-angle limbs (that is, limbs that are growing up) are normally pruned away as they develop because, sooner or later, they will crack under the weight of foliage, ice or snow. If you prune soon after the limb starts growing, the energy will be directed to other parts of the tree where the results will be long term. For the same reason, extremely high-angle limbs (limbs that are growing in the direction of the ground) should also be sacrificed; in time, they will crack for the same reason.
How do you know which limbs are "low angle" and "high angle"?
Start by forgetting the angles. Instead, think of the face of a clock and relate everything about the tree to that. As you saw in mid-January when birch, dogwood, Japanese and sugar maples were pruned, visualizing the numbers on the clock is a flawless way of determining what is to be pruned and what is not.
Think of the trunk of the tree as standing from 6 to 12 on the clock, with limbs coming off the trunk in various directions. The direction of the limb coming off the trunk helps determine whether it's a low-angle limb (to be pruned), a medium-angle limb (to be saved) or a high-angle limb (to be pruned). Here is how to use the clock to decide:
Low-angle limbs are those growing off the trunk (or a branch) in the direction of 12 to 1:30 or 10:30 to 12 on the clock. Prune these limbs now.
Medium-angle limbs are those growing off the trunk in the direction of 1:30 to 2:30 on the clock, or in the direction of 9:30 to 10:30 on the other side. Save these limbs.
High-angle limbs are those growing off the trunk in the direction of 2:30 or below, or below 9:30 on the other side of the clock. Prune these limbs now.
Remove the less desirable limb where two limbs cross. If an inch or so separates two limbs, one growing toward 1:30 and the other toward 2, prune the 1:30 limb and save the other.
Remove all limbs growing downward, no matter where they are positioned on the tree.
Remove all water sprouts from branches. These are the pencil-thin shoots growing vertically on limbs where there has been improved sunlight as a result of pruning in recent years. Cut these sprouts at the base, but expect them to grow back by mid-April. A different treatment in early June will prevent the sprouts from surfacing again.
To promote renewed fruiting of once-active spurs on mature fruit trees, the top canopy should be pruned to increase sunlight in the tree's inner core. This is done by going to 11 and 1 on the face of the clock, and pruning limbs to allow a "wedge" of sunlight into the tree. Normally, wedge pruning removes thin branches cluttering the canopy, but retains thick limbs that extend to the perimeter of the tree. If you wedge prune now, previously dormant spurs will be activated this year and will bear fruit in 1989 and years thereafter.
Remove cracked, diseased and insect-ridden branches. Where trees sustained cicada damage, prune all limbs back to healthy tissue. If you don't prune these branches, new growth won't occur until the cicada-damaged limb falls from the tree.
Finally, if in doubt about pruning, leave well enough alone. Inspect the tree from the opposite side in hopes that problem limbs (low- and high-angle branches) will be more clearly visible. If you're still uncertain, don't prune.
Several other pruning points should be stressed:
When pruning limbs coming directly off the trunk, always leave the bark ridge behind. On the top of the limb, within an inch of the trunk, you will find an irregular scruff of raised bark. On the bottom of the limb, there will be also be a scruff, although it won't be as pronounced as the ridge at the top. In every case, leave this bark ridge behind when you prune, otherwise substantial dieback into the trunk will plague the tree for the rest of its life.
Using chalk, draw a line just beyond the bark ridge on the top of the limb (that is, going away from the tree trunk) to just beyond the bark ridge at the bottom. Having made your earlier cuts far out on the limb to relieve weight stress, begin by cutting upward from the bottom along the chalk line; the final cut from the top severs the limb while protecting the bark ridge. Don't paint with tree wound dressing.
Proper pruning tools are a must. Nothing approaches the safety and ease of the pole tree pruner. Available in assorted lengths, the telescoping pruner makes easy work of limbs 25 to 40 feet up the tree. Read the manual accompanying the pruner before using it.
NEXT WEEK: Feeding your trees for the year.
Jack Eden hosts "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).