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Home My WebLink About2007 11 14 Handed out by Mike MingeaNovember 14, 2007 HANDED OUT TO THE BEAUTIFICATION OF WINTER SPRINGS BOARD MEMBERS AT THE NOVEMBER 14, 2007 REGULAR MEETING BY MIKE MINGEA, CITY ARBORIST. Fa 2007 Florida .Arborist _ ....~. v ~ ;., . Pruning Pointers Proper structural pruning in the landscape will result in safer, longer-lasting trees. By D. Scott Shultz Trees grow in many directions in the landscape. As they get taller and wider, they brush up against buildings and block the view of signs and other important vistas. Sometimes, branches grow lower and droop downwards over sidewalks and streets. It is no wonder many tree maintenance companies are consumed with clearance issues. This leaves little time to address other pruning opportunities, such as strLictural pruning, Structural. pruning is looking at the interior branching patterns of the tree and making cuts to optimize branch strength. Stranger branches help minimize breakage, thus making trees safer and longer lived. Structural pruning focuses on goad branch-to-trunk architecture, These unions are the building blocks of the canopy of the tree. If a branch breaks off at the trunk, decay can proceed down into the trunk of the tree and lead to its removal. As ect Ratio Good branch-to-trunk architecture consists of a small diameter branch relative to the diameter of the trunk (called the aspect ratio}. For example, a 3-inch branch coming. off a 10-inch trunk would have an aspect ratio of 30%. The goal on any branch-to-trunk attachment is to have an aspect ratio of less than 50%, when the branch is smaller in size compared to the trunk, tho union is stronger. This strength is derived from how the tree ex ands in girth every spring. The branch expands in p diameter and lays down branch wood lower on the trunk of the tree. The trunk increases in diameter next and wraps around this branch wood. The branch is "laminated" to the trunk by these alternating wood layers each year. when the branch is the same size as the trunk, this laminating process usually does not occur and there is a weaker union. Branch Protection Zone Another feature of good branch-totrunk architecture is the presence of the branch protection zone. According to Edward F. Gilman and Sharon J. Lily's Tree Pruning -Best Management Practices, the branch protection zone is "a thin zone of starch-rich tissue at the base Of a branch into which chemicals are deposited to retard the spread of discoloration and decay." This zone helps to keep decay out of the trunk. If the trunk starts to decay, this can severely diminish its strength and lead to the removal of the tree. The branch protection zone tends to form in branches with a small aspect ratio. Included Bark Another feature of good branchto- trunk architecture is the absence of included bark. Included bark is "bark pinched between two stems or between a branch and trunk preventing formation of a typical branch bark ridge; an indication of a weak union" according to Gilman and Lily. Included bark reduces the amount of attachment of the branch to the trunk. This can lead to the branch splitting off of the trunk due to a weak attachment. Recognize Branching Patterns Another important part of structural pruning is recognizing the branch pattern along the trunk and throughout the canopy. Branches can be codominant or aggressive. codominant stems are relatively the same size as .the trunk. In fact, oftentimes it is hard to distinguish which one is the trunk or should be the trunk, You can have several codominant stems competing for the apical dominance of the tree. Ideally, you want one trunk in the center of the tree. The codominant stems have a high aspect ratio X90% to 100%). They usually do not have a branch protection zone and can be vulnerable to included bark. Aggressive branches usually have a 50% to 80% aspect ratio. They either grow aggressively sideways or turn upward parallel to the trunk. When they grow sideways, they often Pruning Pointers continued on next page 10 Photo courtesy of Ed Gilman, University of Florida Florida Arboris~~ . _ .. _ Fall 2007 ..... ..,+.. . .ro. 't Y . ~.. t .. .. stick outside the canopy and make the tree unbalanced. They also can have excessive end weight and split out from the tree. or, if they are low in the canopy, they may have to be removed due to clearance issues and can make large pruning wounds on the trunk. When they .turn upwards, they crowd out the normal growth of branches further up the trunk of the tree. Both branch types are not structurally pound for the tree. Ideally, branches should have a small aspect ratio with scaffold branches evenly, alternately, and spirally spaced up anal down the trunk of the tree. Shortening Branches Once you have learned to recognize codominant s~~ns and aggressive branches, one technique used to correct their growth is to simply shorten them (also known as reduction or dropcrotch pn~ning). To shorten a branch, start at the outer edge of the branch and drop down to a crotch or another smaller branch that is at least one-third the diameter of the branch you are removing to make your cut. This effectively slows the growth of the branch by removing food-producing foliage from the branch. Another technique to shorten a branch is to double-drop-crotch prune. This is reducing the branch in two different places by picking another lateral on the remaining branch and making a cut. This helps when you. absolutely want to slow down a codominant or aggressive branch. Shortening also allows other branches to grow into the space once occupied by the codominant stem ar aggressive branch. Timing, Amount, And Frequency If they are healthy, most trees can be pruned year-round in warmer climates. The optimal. time is when the tree is dormant. The least optimal time is .Pruning Pointers continued on page 12 Petzel, Yates, Bluewater, New England, Weaver GAtNESVILLE ROCK GYM 704 S. Main St. Gainesville, FL 32601 (352) 335-4789 x5 Ask for Roger Climbing and Rigging Ropes, Carabiners and Hardware We specialize in Single rope ascent technique. Demonstrations available by appointment. ~ ~~ Quercus virginiana `SDLN' P.P.#12,015 ~. ~~., ~~ ~ `' Lookin for a ,.w~=?'~ <.:.as~~.~.~x~::: ,i,~; % Iar~e matunn~ 21. ~~ yy//~J.:: R Florida Arborist irk Pruning Pointers continued from page 11 during spring flush, when so much of the tree's ever is . gY berng consumed producing new leaves, shoots, and roots. In general, prune no more than 25% of the foliage in an Y one year. Make fewer, larger cuts to maximize your efforts. Younger trees may be able to exceed this amount. Mature trees should be less. Trees can ~be structurally pruned every year. if you do not exceed the 25%- foliage-removal goal. This frequency will depend Largely on how much the tree has been structurall y pruned before. Young trees that have been structurall y pruned will require less structural pruning in the future, Kill Two Birds With One Stone There will always be the immediate concern of clearance issues with trees, when making clearance cuts, take a look at the internal structure`of the tree. Perhaps by making two or three structural cuts, you can also solve your clearance issues. Remember, structural pruning improves the lon - g term health of the tree and reduces its risk in the landscape. ^ TREE Fund Update n v v of g 0 tg 11