How to Keep Your Trees Healthy
Some people wonder what they can do to keep their yard trees healthy and safe. There are a number of really simple things you can do to ensure no additional damage is done to your valuable landscape trees.
#1 Leave them alone! Trees don't really like to be messed with. More often than not, landscape trees survive despite us rather than because of us. Sure, we plant them and water them until they are established, but most trees will do best if they are simply left alone and allowed to grow their own way.
#2 There are exceptions to the first rule, and here they are:
Gently prune them when they are young. Structural pruning can do a lot of good when trees are developing their form and can reduce future problems, such as limb failures.
Control any pest and disease problems- some young trees come from the nursery with pest problems that can keep your trees stunted and struggling to grow. It is much easier to control pests like aphids and scale when the trees are young and easy to reach. For larger trees that are being attacked by insects, like in the case of Hemlock trees, there are systemic insecticides that can be injected into the tree to kill the pest, Hemlock Wholly Adelgid (HWA). Some fungal diseases can be controlled with fungicides but these typically require repeat treatments, up to 3-4 times a year. Many minor problems may also present, such as in the case of oak leaf gall, which is a tree’s reaction to a wasp and typically does not need any treatment but may benefit from improving site conditions.
Inspect the trunk flare for girdling roots. These are roots that encircle the trunk and can literally strangle the tree, reducing the flow of water and nutrients and can even lead to tree failure. When caught early, these roots can be pruned out.
Get a soil sample. Most trees are able to adapt to most soil conditions but occasionally soil conditions will limit tree vigor. Soil amendments can remediate this problem but should be applied with the aid of a soil sample that accurately prescribes dosing.
Mitigation pruning. If you have a mature tree that presents a hazard to your property and want to keep your trees around, the major tool Arborists have is through pruning. Cabling, Bracing, and Propping are secondary options to reduce the likelihood of major tree failure. Not every tree is a good candidate for pruning, and then whole tree removal may be suggested if you cannot tolerate the level of risk in the given scenario. Sometimes tree removal can be an important measure in keeping your other trees healthy, such as removing an apple tree that has fireblight in an effort to reduce spreading the disease.
#3 Avoid over-mulching. “Mulch volcano” is a term that describes piling mulch up onto the tree’s trunk. This keeps moisture in the wrong place and can often lead to decay. Thankfully it's easy to avoid this damage. Mulch should be kept off the lower trunk.
#4 Put mulch in the right place. Following rule #3, mulch needs to be kept away from the trunk. Place mulch 2-4 inches deep and cover up to or past the “drip line”. This is the edge of the canopy. Mulch should be used to create a stable environment for roots. It can moderate soil temperature and moisture which reduces tree stress. Many large landscape trees are not given a big enough mulch ring.
#5 Stop removing all the leaves. Leaves are part of nutrient cycling. When all the leaves are removed, part of the cycle is being disrupted. Instead of removing leaves, allow them to degrade within the mulch ring. This will moderate water, increase organic matter, diminish weeds, and can reduce how much work goes into your landscape, such as mowing and raking.
#6 No digging, grading, or root damage. One of the worst things you can do to a mature tree is to dig, trench, or regrade around its roots. This can cause infection to enter through damaged roots and result in tree death, or worse, whole tree failure. If you must do some digging within the drip zone of a tree, use hand tools and do not damage large structural roots.
#6 Avoid heavy pruning. Overpruning, lions-tailing, topping, and flush-cuts all result in long term problems. If you want your tree to be pruned, be sure to avoid cuts larger than 4 inches and limit the amount of canopy to be removed, especially on mature trees.
#7 Be cautious with fertilizers and pesticides. Damage from herbicide drift can be lethal for trees and over fertilization can result in weird growth and pest problems like aphids which are attracted to the lush growth.
#8 Be aware of your tree species and if there are any pests or diseases that may threaten it. There are a lot of emerging tree problems like Oak Wilt, hemlock wholly adelgid, and Dutch elm disease that could be mitigated if you preventively treat your trees with fungicides or insecticides.
You may have noticed that most things I’ve listed describe what not to do. For most trees, simply leaving them alone, giving them space to grow, and consistent conditions is the best thing for them. If you suspect there may be an underlying problem that is reducing tree vigor, consider consulting with a qualified arborist to determine how to improve site conditions, or remove tree health obstacles.
