Calgary has some unique challenges to gardening, but the rules are the same for most regions. One of the main reasons for tree loss and tree stress is the lack of water. Many people are adamant that they are watering the trees and are concerned that they are drowning their trees.
The Problem with the 10 Minute Watering Technique
The idea that ten minutes of watering a day or the dependence on an automatic irrigation system is sufficient is a bit misleading. If you intend to water your grass or your annual beds, the irrigation system is okay, since it is generally set up to soak down to 3 to 4 inches below the surface. Trees, shrubs and perennials generally have root systems below this depth. (Perennial root systems can reach down to a foot, shrubs have root systems down to 2 to 3 feet deep and trees can be 5 feet deep.)
There are three problems with doing the 10 minute soak:
1. a lot of the water will evaporate
2. you are cooling the soil temperature, thereby reducing the ability of the plant to take advantage of the summer heat to grow during our (too short) growing season
3. the tiny roots of the plant then are following the humidity line up to the surface thereby creating a shallow root system that is vulnerable to the the drying Chinook winds and fluctuations in temperature.
Shallow Root Systems
When you create this shallow root system you are setting your trees, shrubs and perennials for disaster. They may come back one or two years, but after the chronic stress of temperature changes and the lack of water they will eventually succumb and die.
The best example of this is the larger weeping birches that for many years, are beautiful and maybe 20 to 30 feet tall. Then (suddenly) in one winter, they lose a third of the tree right off the top. The top is all dead, and the homeowner is devastated. The tree did what it had to do to survive and let the top third die off. Other trees such as May Day trees and Willows and Shubert Cherries will send out shoots at the base or into the yard. The trees are trying to find new sources of water to help the plant survive.
Spruce trees are notorious for drinking a lot a water, often robbing neighboring trees of the resource. The spruce might look alright but the neighboring tree will have fewer leaves, be struggling and sending out the shoots. Therefore it is important to deep water them as well. One of the main reasons it is difficult to plant anything under a spruce is NOT because of the acidic soil. It is because the roots under the tree have consumed the water, and there is less light and less direct rainfall that can reach the area.
Drought Symptoms on Leaves
You can tell if the tree doesn't have enough water by examining the leaves. If the leaves are dry around the edge of the leaf sometimes to the point of curling up and being crispy, the tree doesn't have enough water. If it is a pine or spruce, the tips of the needles will start to appear yellow and then brown.
Tree Drowning Symptoms
If the tree has too much water, the center of the leaf will be yellow. If it is a spruce or pine the base of the needles will appear yellow.
Those Aphids!
Another signal of lack of water and shallow root system problems is the infestation of aphids. Imagine a stressed fish out in the ocean. Sharks and other predators will seek out the stressed animal. Trees and shrubs are the same. The aphids come, they feed on the juices of the tree and excrete that sticky "poop". The ants love that sugary waste plus they have a wonderful dry environment at the base of the tree (due to the tree siphoning up every drop it can - also to compensate for the aphid infestation). At some point the wasps will join the party. All a person had to do was deep water the roots of the tree and many of these issues would never surface - or at the very east would not be so prevalent.
(As a side note, complaints of dew worms are symptomatic of not watering the lawn sufficiently. When the lawn is been soaked deeply the dew worms will do their work deeper into the soil, thereby not leaving as many heaves and lumps on the lawn surface)
What is Deep Watering?
Think in terms of the size of the root ball of your tree. This is the amount the tree requires for a really good watering. If you deep water the tree once a week (twice a week when being established and depending on the weather) you are helping it develop a really good and deep root system, less susceptible to weather changes and drought conditions. When the tree is susceptible to weather changes, it misreads the spring weather, prematurely opening leaves and blossoms, and vulnerable to spring snow storms which will freeze off those buds, and blossoms.
You can soak the roots by placing a hose at the base of the trees at different quadrants. Depending on the size of the tree, you may have to place the hose anywhere from 4 to 8 positions around the tree and leave the hose to soak anywhere from 20 minutes to an hour at each position. If it is a new tree, around 4 feet in diameter (edge to edge of the tree leaves or crown), once or twice a week I generally do a two point watering with a soaker hose for 15 to 20 minutes in those two sides of the tree base. You don't want the base to be sopping wet so you do have to watch things in the first time you do this to gage things. Some people find the deep root water/feeders a really good solution. I think they have merit though in some of Calgary's clay soil it may be difficult to place the feeders.
Preparing and Surviving the Winter
In the Fall, (Sept. 15 to Oct. 31) deep water the roots of the perennials trees and shrubs to create a root ball of ice, thereby locking in the water for use in the spring and keeping the plants dormant through the critical months of January, February and March. If your property is dry during these months the "ice cube" of roots may be reduced, again putting the plants at risk to Chinook and drying winds. I go out and bucket water the plants with cold water. In the case of pines, spruces, junipers, cedars and yew trees, throw an extra bucket of water onto the foliage. I have found this to be helpful in preventing or at least mitigating wind burn.
In Summary
Each week, one or two really good soaks of the trees, shrubs and perennials really is more beneficial and a better use of the water we have. The grass and the annual beds generally benefit from this focus on the trees. If you do fertilize, only do it once every two weeks and stop fertilizing in the first week of August. This will help the plants to go into dormancy for winter.
