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Trees and Turf
Trees and turfgrass are two very important, though not always compatible, aspects of the horticulture industry. Sometimes the desires of the arborist and turf manager come into conflict, for the needs of the two plant types can differ greatly from one another. In fact, some species of both plant types can produce alleliopathic (poison) compounds to reduce competition from each other. Nevertheless, thoughtful consideration as to plant selection and good cultural practices can often mitigate those differences.
I suppose the single most important determining factor as to whether or not you?ll have a successful tree/turf relationship is in the selection of the right trees for the site and to a lesser extent, having the right turfgrass to go with the trees.
Plants can be very complicated, so I like to try and use some generalizations when I?m thinking about my plant?s needs. One of the generalizations I use most frequently is that turf is a plant that needs frequent irrigations that penetrate to a depth of 6 to 12 inches, whereas trees are plants which need less frequent watering, but to a depth of about 24 inches. While most of a tree?s fine roots coexist in the top 6 to 12 inches, along with the turf roots, the deeper irrigation is necessary to help encourage the establishment of the larger roots deeper in the soil, and may also allow the tree to pick up nutrients where no turf roots exist. I also break trees into generalized categories of high, medium and low water users, some of which are much more compatible to life amongst the grass. While all three types like deep and wide soaks, the difference between the three is in how frequently irrigation is needed. High water use trees like frequent soaking, and often thrive in the relatively wet soils associated with turf, moderate water users like less frequent irrigation, yet can still manage to do well in a lawn situation, while low water users (read as ?desert trees?) don?t like those wet conditions. It?s the desert trees that usually suffer the most in a turfgrass setting.
Using the right tree in the right situation can make all the difference. High water use trees, while generally excelling in turf situations, can also help solve turf problems. High water use trees can mitigate saturation problems in low laying areas by using and removing some of that excess water. Some of the species that seem to do better in such conditions are the ?bottomland? species, such as members of the Salix (Willow), Populus (Poplar) and Platanus (Sycamore) genera. Ligustrum (Privet) and Magnolia also seem to benefit from the wetter conditions associated with turf.
Moderate water use trees are also often very tolerant of planting in or near turf. Fraxinus (Ash), Ulmus (Elm), Chitalpa and Pistache (Pistachio) come immediately to mind.
However, it?s the desert trees that suffer most and often die in lawn situations. Prosopis (Mesquite), Cercidium and Parkinsonia (Palo Verde), Acacia, Eucalyptus and Schinus molle (California Pepper) all struggle and suffer a variety of symptoms when planted in and watered with grass. Eucalyptus and California Pepper have a tendency to become spindly and chlorotic, while the others often exhibit extremely rapid and weak growth habits, filled with long brittle wood and weak crotches. Research has shown that such unnaturally fast and lush growth can also reduce the trees tolerance to disease and insect pests. In addition, desert trees that are potentially cold sensitive are much more likely to suffer damage, or to suffer more extensive damage, in periods of prolonged and deep cold, when they?re pumped full of water, as is almost always the case if they?re planted in turf.
Unfortunately, as the managers of properties, we often don?t have the chance to choose the species and locations of our trees. We must then deal with the site conditions as they exist, and build a maintenance program that thoughtfully considers the needs of the plants under our care. There are some simple and straightforward steps we can take that will help promote and protect these two very different plant types.
Perhaps the most important of these steps is to mulch around the trunks of our trees. This has several important benefits, especially early in the life of the tree. Young trees have greatly enhanced health and vigor when turf is replaced with organic mulch just a few feet in diameter around the trunk. Competition with turf for air, water and nutrients is eliminated as the tree first becomes established. If small perennials are planted in the mulch, they do provide some competition, but usually much less so than does turf. The removal of the turf from around the trunk also eliminates that most horrid of diseases, line trimmer blight. While protection of the trunk from the assaults of line trimmers and mowers is important throughout the life of the tree, it is especially critical for young trees with their narrow trunks and thin bark. The need to protect our trees from this kind of damage cannot be overstated. In addition to the above benefits, organic mulches moderate soil temperatures, improve soil structure, increase microbial activity, and improve air, water and nutrient retention ? and, they look great to boot. Their use eliminates the need to nurse turf along in what is often the most difficult place to grow it, around the base of a shady tree. Finally, mulching can reduce the incidence of some crown gall and root rot diseases, for when mowers damage tree roots, they often also induce and spread such diseases, some of which can remain active in the soil for many years. Use organic mulches by placing 2 to 5 inches deep all around the trunk, but be careful to keep it from laying in any thickness against the trunk. Of course, the larger the area mulched, the greater the advantage for the tree.
Another consideration for arborists is how we can properly prune our trees to make life easier for the turf (and turf manager) below. A good thinning and crown cleaning of a tree will often increase the light penetration for the light starved turf below. Also, a long term and gradual lifting of the canopy can make a dramatic difference in light availability to any understory plants. Be cautious not to over prune in your enthusiasm to increase light penetration.
Another beneficial practice is to use deep root water probes to inject water into soil profiles below the 6 to 12 inch depths. Shallow aeration often benefits turfgrass only, because grass roots are much more aggressive and adventitious, and will quickly take over the improved soil areas. However, the deeper aeration will encourage air availability and root penetration deeper in the soil profile, where trees are more likely able to take advantage.
With forethought and considerate management, turf and trees really can peacefully coexist in an environment where both can thrive. Now, if only we can find similar solutions for the Middle East. Hmmmm ? perhaps if we were to heavily mulch the West Bank and Jerusalem ?
I suppose the single most important determining factor as to whether or not you?ll have a successful tree/turf relationship is in the selection of the right trees for the site and to a lesser extent, having the right turfgrass to go with the trees.
Plants can be very complicated, so I like to try and use some generalizations when I?m thinking about my plant?s needs. One of the generalizations I use most frequently is that turf is a plant that needs frequent irrigations that penetrate to a depth of 6 to 12 inches, whereas trees are plants which need less frequent watering, but to a depth of about 24 inches. While most of a tree?s fine roots coexist in the top 6 to 12 inches, along with the turf roots, the deeper irrigation is necessary to help encourage the establishment of the larger roots deeper in the soil, and may also allow the tree to pick up nutrients where no turf roots exist. I also break trees into generalized categories of high, medium and low water users, some of which are much more compatible to life amongst the grass. While all three types like deep and wide soaks, the difference between the three is in how frequently irrigation is needed. High water use trees like frequent soaking, and often thrive in the relatively wet soils associated with turf, moderate water users like less frequent irrigation, yet can still manage to do well in a lawn situation, while low water users (read as ?desert trees?) don?t like those wet conditions. It?s the desert trees that usually suffer the most in a turfgrass setting.
Using the right tree in the right situation can make all the difference. High water use trees, while generally excelling in turf situations, can also help solve turf problems. High water use trees can mitigate saturation problems in low laying areas by using and removing some of that excess water. Some of the species that seem to do better in such conditions are the ?bottomland? species, such as members of the Salix (Willow), Populus (Poplar) and Platanus (Sycamore) genera. Ligustrum (Privet) and Magnolia also seem to benefit from the wetter conditions associated with turf.
Moderate water use trees are also often very tolerant of planting in or near turf. Fraxinus (Ash), Ulmus (Elm), Chitalpa and Pistache (Pistachio) come immediately to mind.
However, it?s the desert trees that suffer most and often die in lawn situations. Prosopis (Mesquite), Cercidium and Parkinsonia (Palo Verde), Acacia, Eucalyptus and Schinus molle (California Pepper) all struggle and suffer a variety of symptoms when planted in and watered with grass. Eucalyptus and California Pepper have a tendency to become spindly and chlorotic, while the others often exhibit extremely rapid and weak growth habits, filled with long brittle wood and weak crotches. Research has shown that such unnaturally fast and lush growth can also reduce the trees tolerance to disease and insect pests. In addition, desert trees that are potentially cold sensitive are much more likely to suffer damage, or to suffer more extensive damage, in periods of prolonged and deep cold, when they?re pumped full of water, as is almost always the case if they?re planted in turf.
Unfortunately, as the managers of properties, we often don?t have the chance to choose the species and locations of our trees. We must then deal with the site conditions as they exist, and build a maintenance program that thoughtfully considers the needs of the plants under our care. There are some simple and straightforward steps we can take that will help promote and protect these two very different plant types.
Perhaps the most important of these steps is to mulch around the trunks of our trees. This has several important benefits, especially early in the life of the tree. Young trees have greatly enhanced health and vigor when turf is replaced with organic mulch just a few feet in diameter around the trunk. Competition with turf for air, water and nutrients is eliminated as the tree first becomes established. If small perennials are planted in the mulch, they do provide some competition, but usually much less so than does turf. The removal of the turf from around the trunk also eliminates that most horrid of diseases, line trimmer blight. While protection of the trunk from the assaults of line trimmers and mowers is important throughout the life of the tree, it is especially critical for young trees with their narrow trunks and thin bark. The need to protect our trees from this kind of damage cannot be overstated. In addition to the above benefits, organic mulches moderate soil temperatures, improve soil structure, increase microbial activity, and improve air, water and nutrient retention ? and, they look great to boot. Their use eliminates the need to nurse turf along in what is often the most difficult place to grow it, around the base of a shady tree. Finally, mulching can reduce the incidence of some crown gall and root rot diseases, for when mowers damage tree roots, they often also induce and spread such diseases, some of which can remain active in the soil for many years. Use organic mulches by placing 2 to 5 inches deep all around the trunk, but be careful to keep it from laying in any thickness against the trunk. Of course, the larger the area mulched, the greater the advantage for the tree.
Another consideration for arborists is how we can properly prune our trees to make life easier for the turf (and turf manager) below. A good thinning and crown cleaning of a tree will often increase the light penetration for the light starved turf below. Also, a long term and gradual lifting of the canopy can make a dramatic difference in light availability to any understory plants. Be cautious not to over prune in your enthusiasm to increase light penetration.
Another beneficial practice is to use deep root water probes to inject water into soil profiles below the 6 to 12 inch depths. Shallow aeration often benefits turfgrass only, because grass roots are much more aggressive and adventitious, and will quickly take over the improved soil areas. However, the deeper aeration will encourage air availability and root penetration deeper in the soil profile, where trees are more likely able to take advantage.
With forethought and considerate management, turf and trees really can peacefully coexist in an environment where both can thrive. Now, if only we can find similar solutions for the Middle East. Hmmmm ? perhaps if we were to heavily mulch the West Bank and Jerusalem ?
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