Room To Breathe
A tough place to be on a hot, humid day is a golf course. It is even tougher if you are the turfgrass. Add in restricted air movement and low exposure to sunlight, and you have a recipe for problems. These environmental conditions encourage the establishment and proliferation of diseases and these same conditions weaken the ability of the turfgrass to combat them. What would create higher humidity, restrict air movement and reduce exposure to sunlight? Sounds like a tree.
Trees, while not essential to the game of golf, certainly add to the aesthetics and challenges of it. They delineate boundaries, serve as convenient rest spots for golfers and add character to the course. Trees are so much a part of golf courses that almost 1 in 10 golf courses in the United States have a “leafy” reference to its name. But trees can also be a liability to a golf course. They can go beyond adding challenge and just increase luck as the flying golf ball bounces off a tree like it's the metal ball in a pinball machine. Trees also can send roots in places we do not want them, such as putting greens, tees and cart paths. Trees create a microenvironment that, while pleasing to golfers, is hostile to turfgrass.
The area beneath the tree, the dripline, the outermost extent of its branches, is a tough environment for turfgrass. There is a reduction in light intensity and a shift in light quality within this environment. These lower light levels are deficient in the red and blue portions of the light spectrum resulting in spindly growth of the turfgrass. The turfgrass has longer, thinner leaf blades, reduced density, shallower roots and less wear tolerance. These same trees that filter light also can alter or restrict airflow resulting in an environment that is favorable for diseases.
LET IN THE LIGHT
So how do we improve airflow and light? You start by pruning; basal pruning. You probably do not need to keep all the trees on your course. While I am trained as a forester and trees are important to me, I believe there are too many trees on most golf courses. When I stand at the tee and look down a fairway and feel I am in a bowling alley rather than on a golf course I know there are too many trees, some need to go. While it may seem like I am stating the obvious — trees grow. The small tree planted near the tee 20 years ago seemed like a good idea at the time. It provides shade for golfers while they are waiting but now that it looms over the tee choking the life out the turfgrass and blocking the use of the tee, you are probably having second thoughts.
Trees are especially a problem for putting greens and tees. These are high-traffic areas that draw a lot of attention from golfers. Too many golf courses were designed to handle fewer rounds than they are currently enduring. This wear is compounded by overhanging trees that interfere with the line of play and may restrict the golfers to only a portion of the usable area of the tee. Turfgrasses in putting greens and tees are also more vulnerable to environmental stresses than turfgrasses on the fairway, and trees can compound these problems here far more than trees lining fairways or in the roughs.
How to remove trees? It can be a hassle — members usually do not like to see trees coming down — and more than one golf course has resorted to the “midnight tree removal.” (A golf course superintendent once asked me if there were any OSHA regulations that prevented felling trees at night!). My suggestion is to start the removal process by developing a plan focusing first on putting greens and tees. Sunlight should be reaching the tees and putting greens — all parts of them — for more than half the day. There should be sufficient airflow to allow the turfgrass to dry quickly in the morning. If you already have fans out this is probably a good clue that the trees and shrubs are too thick. Ideally the outer branches of the trees should not be within 30 or 40 feet of the putting green. Trees are often set closer to the tees than greens; particularly behind them to create a barrier between holes, but even with tees the more distance between trees and tees, the fewer the problems. You cannot remove all the trees, of course, but selective removals and proper pruning of the remaining trees can usually significantly reduce the problems of airflow and light.
Cutting holes in the direction of prevailing wind can increase airflow in the vicinity of putting greens and tees but must be done carefully. Trees that were surrounded by other trees may not be windfirm and might fail when suddenly exposed to wind. Wind tends to speed up as it flows through a narrow opening and these new edge trees are subjected to high wind loading. Trees that become part of these new edges must be capable of withstanding the stresses imposed by these stronger winds. The best candidates will have a good trunk taper and no evidence of cavities or hollows. The root collar area should also be inspected on these new edge trees. Signs of decay, such as fungal fruiting bodies, are indicators that the tree's roots may not provide adequate support and this tree is not a good candidate for leaving.
In addition, try to reduce the number of trees on the northeast to southeast side of tees and putting greens. Morning light is optimal for turfgrasses growing on putting greens and tees. In addition, extended dew in early morning creates favorable conditions for disease development and this early exposure will help the turfgrass dry out sooner in the day. Conifers especially should be targeted for removal if they are on the south sides of tees and putting greens. Their dense and permanent (rather than seasonal) shading can delay thawing and prolong ice and snow cover.
The trees that remain after removal have been completed near tees and putting greens may still require pruning to improve air circulation and the turfgrass access to sunlight. Pruning can help but how it is applied is very important. Too often the practice of “spiral pruning” is employed where branches are removed in a spiral pattern up though the tree's canopy. In other instances crown thinning, often defined as the selective removal of branches to increase light penetration and air movement, is performed. However, neither method appreciably improves airflow or light.
The way pruning should be applied to improve airflow or light is dimensional pruning — changing the shape of the canopy. This is best applied — for the tree and turfgrass — as crown raising. Crown raising involves the removal of the lowest branches. The lower branches are usually the least efficient branches in the tree, as they are the heaviest shaded, and the ones that are contributing the least to the carbon resources for the tree.
Removing these branches will improve airflow, particularly if any shrubbery is removed from the vicinity. The removal of these branches will also increase the amount and duration of light that reaches the turfgrass in the morning and afternoon. The number of low branches that are removed is dependent on the location of the tree. Trees near the backs of tees can have lower branches than those by putting greens. Generally you want the trees elevated to at least 10 or 12 feet.
Still, removing even these branches can harm the tree, so be careful when implementing this process. Do not remove too many branches at one time, particularly on mature trees. Limit the annual of live branches to no more than 15 percent of the total canopy on young trees and less (perhaps only 5 percent) on mature trees. The location of these branches to be removed is also an important consideration. While the focus is removing the branches from the lower canopy, removing too many at one time can weaken the tree. A good rule of thumb for young trees is that at least one-half of the foliage should be on branches that originate on the lower two-thirds of the tree. You might want to begin by removing only a branch or two a year until the desired clearance is achieved. On mature trees the loss of the lower branches can seriously harm the tree. If these are large diameter branches the removal may result in extensive decay and increased stress on the lower trunk. Ideally the crown raising has been accomplished as a means of training young trees rather than waiting until the tree is mature. If lower branches need to be removed from a mature tree, do it over several years. Have a little patience, the problem did not occur in a day, you are not going to correct it in a day either. If the tree was important enough to keep it is important enough to do the pruning properly and in moderation.
ROOM TO GROW
The proverb about fire (“good servant, bad master”) could apply equally true for trees on golf courses. Carefully designed plantings — to anticipate future growth — and proper maintenance of these trees can add much to the enjoyment of the game by the golfer and reduced headaches for the golf course superintendent. Trees that are randomly scattered across the course, particularly those choking tees and greens can affect the game and create short tenure for the superintendent.
Dr. John Ball is a professor of forestry at South Dakota State University (Brookings, S.D.). He frequently speaks to golf course superintendents around the country on golf course tree management.
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