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- LEAF Learning Garden
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The majority of tree roots grow outward not downward. Approximately 90% of a tree’s roots are found in the top 12-18 inches of soil and can extend out up to three times the height of the tree. These “feeder” roots must compete with grass and other plants for the water and oxygen they need for photosynthesis and growth.
Applying a mixture of woodchips, leaves and compost is one of the best things you can do for your tree’s health. The mulch mimics a natural forest floor, keeping the soil at the base of your tree moist, adding organic matter as it decomposes and reducing competition from grass and weeds. Spread mulch in a circle around your trees as far out as you are willing (the bigger the circle the better for the tree), but ensure that it is not more than three inches deep so that roots can still get oxygen. Keep mulch in a doughnut shape, ensuring it is not touching the trunk as this can cause moisture build up at the trunk base.
The most important factor in growth rate and vigour of a tree is water. Toronto has experienced severe drought for the last several summers. When it does rain, most of the water runs off paved surfaces into the storm sewers, never reaching the trees that desperately need it. Most trees (even large, mature ones) don’t get the water they need. Almost every tree in Toronto will experience drought stress this summer, making them vulnerable to pest and disease attacks.
The soil under the mulch around your tree should always feel slightly damp and cool. Check the soil around newly planted trees two or three times a week. If it feels dry and/or hard, then run for the hose!
For the first two years after planting, you should be diligently watering your tree approximately twice per week. Place a hose (without nozzle) at the base of your tree on a very slow trickle for approximately 15 minutes (or give 3 to 4 buckets). In the third year, once your tree has established a deeper and wider root system, change the watering frequency to one hour, once per week (to give your tree periodic, deeper soakings). The best way to do this is to place a soaker hose (which slowly oozes water from the length of the hose) on the ground in a spiral out to the edge of the tree's canopy. If you don’t have a soaker hose, you can place a hose without a nozzle in the root area of your tree on a very slow trickle. Move the hose to a new area under the tree periodically to ensure all roots get even watering. Never use a sprinkler to water, since wet leaves are often prone to fungal disease.
It is possible to over-water trees as well. Ensure that there is no standing water under your tree. If the soil is sopping wet after watering, you may need to reduce the duration and/or frequency. This is usually only an issue in poorly drained clay or compacted soils.
Newly planted trees sometimes require temporary staking. This is usually only the case if the tree is at risk of vandalism, or if it is large and at risk of blowing over in the wind. It is preferable to plant smaller trees with less top growth. Smaller trees will move in the wind, but are unlikely to blow over. Some movement is good, since root and trunk growth will respond and anchor the tree more securely.
If you do stake your tree, use only soft, flexible materials that will not cut into the bark. Ties should be loose and stakes should be at least two feet out from the tree. Always remove stakes and ties after one year. As the tree grows, ties can cut into delicate conductive tissue located just under the bark of the tree, causing serious damage.
Staking is not the way to deal with leaning trees. Trying to pull or force a tree to grow in a certain direction can cause severe structural damage and can actually worsen the lean. It is better to remedy the situation causing the lean.
Sometimes trees will lean if too much growth has occurred on top before the trunk can support the weight. This often happens after lawn or garden fertilizing causes a rapid rush of top growth. Weight should be removed by using proper pruning techniques. The tree will usually resume a more upright position once the extra weight is removed.
As trees get established and begin to grow, they may lean if they are reaching for light. It is best to correct this problem by removing the source of the shade. This may mean pruning overhanging branches of other trees. Once the light reaches the younger tree evenly, it should compensate with growth and straighten itself.
During the first three years after planting, only dead, diseased or damaged branches should be removed.
As trees grow, they do not necessarily need to be pruned further. However, if there are complicating issues with branch structure, it is best to correct them when the tree is young. Structural pruning is usually done three to five years after planting, depending on species and rate of growth. This may include removing branches that rub, grow too closely together or grow in undesirable directions.
Pruning removes leaves from a tree and therefore reduces its ability to produce food. Never remove more than a quarter of the leaf area in any one year. Do not use wound paint after pruning, as this may interfere with the natural would closure and may actually accelerate decay.
It is very important that proper cuts be made in the right locations, using the right tools. Please research proper pruning techniques before undertaking any work yourself!
Trees should only be pruned by certified arborists -- trained, tree care specialists who have the knowledge and equipment to do the job. Make sure the arborist you hire is certified and has adequate insurance, and don’t be afraid to ask for references. To locate a certified arborist in your area, contact ISA Ontario at 1.888.463.2316 or visit www.isaontario.com
Pests and disease problems are usually a sign that a tree is under stress. Its natural ability to resist attacks may have been reduced by a combination of factors. Investigate your yard and try to identify all of the possible stresses your tree faces. Remember that your tree should be well mulched, regularly watered and protected from physical damage (including roots). Improper staking and/or pruning can also cause stress. Alleviate the stresses to improve the health and vigour of your tree. If only the symptoms (pests or disease) are treated, it is likely that the tree will continue to suffer.