Despite cold temperatures and snow, major garden work is on tap this weekend. Specifically, you are on deadline for pruning so-called "bleeder trees," the likes of birch, dogwood, Japanese and sugar maples. Pruned now, exposed tissue will callus quickly to prevent the loss of energy when the sap rises just four weeks from now. If you delay pruning, valuable food will be lost.
Thankfully, not all bleeder trees will need attention now. If you pruned a year ago, no cutting need be done for a few years, aside from removing limbs devastated by the bronze birch borer or other pests; such cosmetic pruning usually is done during the growing season as damage is spotted. However, if you've never pruned or haven't done so in recent years, you would do well to check these trees this weekend and prune as quickly as possible. If pruning is needed but you're unable to do it yourself, contact a tree maintenance firm to have the work done.
Incidentally, pruning of bleeder trees has usually been timed for the last days of January, but the schedule has been moved forward by two weeks this year because some trees did not callus in time last winter to prevent the loss of food when the sap started rising about Washington's Birthday. Mid-January pruning will eliminate the problem.
As for tools, you're almost certain to need a pole tree pruner. These telescoping pruners extend to heights of about 30 feet, allowing you to prune most trees without climbing a ladder. For the moment, you may want to rent a pole tree pruner, but watch for sales in the coming weeks so you have your own pruner for the late February pruning of other trees.
Widely grown in the Washington area, the Japanese maple is almost certain to need some cosmetic pruning. These slow-growing plants are usually left intact due to the commonly held belief that they do not require pruning because of their graceful configuration. Actually, to preserve the graceful lines of the tree, careful pruning is needed every two or three years.
First, remove any cracked or diseased limbs, always cutting back to healthy tissue. In making the cut, prune to within a quarter-inch of two leaf buds (long and thin in appearance) so a pair of side shoots develop this spring; if you don't prune along these lines, no growth will develop on the limb for some time.
Second, the symmetry of the Japanese maple is usually camouflaged by excessive growth in the core of the tree. To understand this, stand back 10 to 15 feet and focus on the woody branching in the center of the plant. Some undulating branches will be evident, but if you can imagine lots of leaves on the branches, you'll quickly see that the dense foliage will hide the limb structure. This structure is what makes the maple so valuable.
Make sure your pruning shears are razor sharp, then selectively prune this twiggy inner growth from the maple, particularly the "dissectum" species, which includes the lace-leaf maple, red filigree lace, crimson queen, ever red and dozens more having red, green and variegated leaf colors. By eliminating these brushy, pencil-thin growths in the core, plant symmetry will be restored; no pruning will be needed until 1991.
Certain to need attention now is the sugar maple, especially mature trees 50 feet tall and higher; these trees produce the maple syrup you know so well.
To understand the pruning scenario for maples, picture the face of the clock. The main tree trunk runs from 6 to 12 on the clock, and the side branches and limbs come off the trunk in multiple directions. By determining the "angle" at which these limbs come off the trunk, you will be able to prune the tree knowledgeably.
Mentally superimpose the face of the clock over the tree. Some limbs will jut off the trunk in the direction of 1 o'clock, others seeming to grow at 2:30 and 3 o'clock. You don't have to identify angles and such, only how the limb is positioned on the face of the clock.
Good, healthy limbs are those growing between 1:30 and 2:30 on the clock, or between 9:30 and 10:30 on the opposite side. These branches are strong enough to support the weight of all foliage or ice and snow during the winter. Leave these branches alone.
Prune limbs growing in the direction of 12 to 1:30, and those growing below 2:30 (or below 9:30 on the other side of the clock), and limbs between 10:30 and 12. Such limbs will not support full foliage growth and are likely to crack under snow and ice loads over the winter.
Watersprouts (those pencil-thin twigs growing vertically on the low limbs) should also be removed. Cut these sprouts now; they will regrow by midspring, at which time you'll pull the new sprouts with your hands and stop future sprouts from growing.
Check branches that cross one another and are separated by only a few inches. Remove the least desirable branch. For example, if you have crossing branches growing at 1:30 and 2:30, remove the 1:30 branch. If the limbs were at 1 and 2, remove the 1 o'clock limb.
Remember when pruning limbs near the main tree trunk to leave the bark ridge collar behind. This is the scruffy bark found on the limb near the junction with the trunk. Check top and bottom of the limb for this raised bark collar, then prune so you leave this ridge intact. Dieback is assured if you remove this collar when pruning limbs on any trees.
With dogwood, pruning is mostly cosmetic. Remove dead, cracked or diseased limbs. Against your better judgment, don't prune limbs jutting off the trunk that make it impossible for you to cut grass under the dogwood. Leave these limbs intact, but consider mulching under the dogwood come April to eliminate the grass altogether. Extend the mulch to cover the soil a few inches beyond the drip line, diking the mulch so water is channeled to the roots instead of flowing away.
Finally, check canoe and paper birch to see if pruning is needed. Focus exclusively on upper limbs for evidence of damage last year by the bronze birch borer. The evidence includes outer bark flaking off some pencil-thin limbs and raised S's on these limbs. This raised tunnel marks the winter quarters of the borer. Prune all such limbs back to healthy white tissue; leave a stub of two or three inches so new growth may start there in April.
Jack Eden hosts "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).