by Ross Latham
One of the biggest worries of homeowners for their yards is “Are the trees in my yard going to survive this summer?” (We’ll talk some more in a later article about the other big worry of homeowners: winter)
You’ve just finished planting a new tree as the centerpiece to your yard. After all, early spring is the perfect time to plant for the optimum growth of your trees. And in late spring your hard work will have paid off. But now comes summer, and new needs for your trees. Surviving that first summer is especially key for trees, and is, of course, still important in years ahead.
Fortunately it’s just a matter of proper maintenance and any tree can beat the heat. It’s only a matter of understanding a few essentials and one can have healthy trees that last the year round.
First let’s cover soil. You need to take a look to see what type of soil you have and then take steps to improve it on a gradient. If the soil you have is mostly clay then aeration will help provide oxygen needed for optimum plant health. In general trees do not need as much fertilizer as do lawns, but in our generally high pH soils, nutrients, such as nitrogen, iron, zinc and manganese, can be added. You can gain a clue to the soil quality if you note the color of leaves and needles. If they look sickly or light colored, that is a clue that additional nutrients may be in order. If you’re concerned about soil health you might consider having your soil tested. Also, different soil types require different amounts of irrigation. Clay soils will typically need less water because they hold it, than say a sandy or loamy based soil.
Now, of course a big one is water. This is very evident with newly planted trees. They possess a smaller percentage of their original roots and they have to be closely monitored and watered carefully. During extended periods of drought even large established trees need to be watered. A single, large tree can transpire (to give off vapor containing waste products through the stomata of plant tissue) more than 100 gallons of water on a typical summer day.
A few pointers: don’t assume you are watering a tree when you are watering your lawn. Most of the water may go to the lawn, which has many roots competing with tree roots. Thatch in the lawn acts to repel water, and different soil types make water penetration very difficult in many cases. Soaker hoses and drip systems can be useful tools for applying water to dry soil. You should water an area at least as wide as the branch spread, but well established trees often have extensive root systems that extend far beyond the tips of the branches and will benefit from water applied to the soil outside the branch spread as well. Root feeding/watering probes are useful tools for irrigating trees as long as they are not inserted into the soil deeper than 12 inches and are moved frequently.
A few cautions: As a rule of thumb, soil needs to be moist to between 12 to 18 inches of depth for most trees and shrubs. Watering too frequently can also kill trees. Always check the moisture status of the soil around your tree before watering (use a hand trowel or soil probe). If possible, avoid applying chemically softened water to trees. Frequent use of softened water may harm soil structure and injure trees.
Next let’s cover mulch. The purpose of mulch is to conserve moisture and suppress weeds around the tree. Ironically the opposite of these are its cons, as in certain mulches can bring about weed problems (if there are any weed seedlings in the mulch) or block moisture if it’s put on too heavily. I always advise homeowners to apply mulch with caution, never allow the mulch to pile up on the trunk. Keep all mulch clear of the trunk flare at the base. 90% of the time it can do what’s wanted, but you have to take care that you don’t suffocate the tree. Organic mulch is generally better, inorganic mulches tend to sink in small traces into the soil. Organic mulches decompose naturally.
These are a few pointers to set you in the right direction. If your trees have more trouble than this surviving the summer then contact a tree care specialist to come out and take a look at it. The problem might not be the heat, there are tree diseases out there and there could be other factors plaguing city trees. But the above should cover a majority of cases. Then you can beat the heat yourself by sitting in the shade of your tree with a cool drink in hand.
Ross Latham is owner of Big Trees Inc. (http://www.bigtreesupply.com) in Snohomish, WA, one of the largest Seattle tree nurseries (see inventory at http://bigtreesupply.com/sales-inventory/), specializing in tree transplanting. Visit us at http://www.bigtreesupply.com/blog/