Irrigating Trees in the High Desert
As mentioned in our previous blog, trees are beneficial to the residential landscape for many reasons. Trees provide privacy and can make us feel comfortable in our homes while providing habitat for wildlife and increasing property values. Trees are beneficial until they become sick, diseased, and susceptible to damage and then the tree is a liability instead of an asset. So, how do you protect one of your largest landscape assets? The answer, proper irrigation.
Irrigating trees in the High Desert is crucial for the developmental success of the tree, no matter which variety you plant. In Central Oregon, it is best to choose a tree that is adapted for our hardiness zone and that also has a low to moderate use of water. Even a tree that is a low water user will need supplemental irrigation to thrive in the High Desert. The soil profile is shallow and there is not a lot of area to retain water for plant availability. Soil is very important when it comes to irrigation practices and our next blog will look more closely at soil and how it affects irrigation applications.
The first thing to understand about irrigating trees is that trees use more water than any other landscape plant. During the establishment period (3 growing seasons) trees need water not only during the summer but also during the winter months, especially if the ground is dry and the weather is unseasonably warm, like our recent January. Many trees die in Bend and Central Oregon because they did not receive enough water during their establishment time.
BEFORE: A newly planted tree irrigated with drip was not adequate for tree establishment. Emitters were installed on downhill side of trunk with both emitters in the same location, and emitters were not large enough to apply the amount of water needed.
AFTER: Drip irrigation was renovated with emitter line to apply water more evenly under the tree canopy with more emitters on the high side of the slope to allow gravity to move water across the root zone. Drip was also simplified with only one point of connection from the 1/2” drip pipe instead of two, reducing potential for leaks and damage.
The next question to answer is how much water does a tree really need? You can determine how much water a plant needs based on its canopy size. A plant canopy diameter of 10 feet needs 7.5 gallons per day in a warm environment for a moderate water use tree, 9.5 gallons in a hot environment, approximately 52-67 gallons per week. Many trees are not planted or irrigated in a way to provide the necessary amount water. Often trees are planted in lawn areas and are irrigated with the lawns without supplemental irrigation. Watering to the needs of the tree would drown the lawn and create other issues. The lawn and tree are competing for the same water and the lawn is more vigorous at stealing water than trees are. The trees will often lose the battle with the turf grass and trees often have the added stress of lawn mower blight and other maintenance injuries.
A Ponderosa Pine fell in Gilchrist, OR in August 2008 for no apparent reason.
The most important thing to keep in mind when considering trees in your landscape is that they will perform best when they have their own dedicated irrigation. It is best to have your trees on their own zone of irrigation, either bubbles or drip, and to not assume that the trees get enough water when the lawn or other landscape area gets water. Irrigation needs to be delivered slowly in order to be absorbed by the soil and prevent run off. Back in 2008, a tree fell in Gilchrist, OR and the picture in the paper showed a beautiful, well-maintained landscape and healthy green lawn with a fallen Ponderosa Pine right in the middle of it. The picture also shows the turf and tree roots together and a few inches of moisture in the soil profile. This news article is a great example of the need to irrigate tree separately from lawns and the damage that can happen when residential trees aren’t irrigated properly. From the picture, you can assume that the homeowners cared for their landscape and the tree was not neglected from the aspect of not being cared for. The tree was neglected because it was unknown that the tree needed supplemental irrigation. Water Whys Irrigation is glad to know that no one was injured when this particular tree fell and hopes the insurance was easy to deal with regarding the claim for the property loss. https://www.bendbulletin.com/localstate/tree-falls-in-gilchrist-and-disbelief-follows/article_ccbfb32a-6860-52a3-9f56-53d431d489ad.html
If you have trees on your property that you want to protect and would like to make sure your irrigation is adequate for your trees to thrive, contact Water Whys Irrigation and schedule your appointment today.