Watering your trees is essential for their health and survival. All trees will vary on volume and frequency of watering, but in the end they all need water. In the urban forest, different challenges are incurred regarding water access for trees compared to the natural forest setting. We’ll talk about what influences a tree’s need for water, things you can do to better reflect that natural setting in your landscape and tips on watering techniques to keep your trees looking great!

Established trees typically prefer about 1” of rainfall per week. In a natural forest setting, the forest floor is full of leaf litter and other organic matter. This creates what is referred to as the duff layer. The duff layer helps retain water for the trees and slowly breaks down over time helping to enrich the soil and all the microbes that live within it. In our urban forest, there is no duff layer as trees are typically in paved areas or lawns. Utilizing a natural mulch around the base of your tree will help serve as the natural duff layer. Retaining water, protecting the fine roots of your tree from extreme temperatures and help improve organic matter in the soil surrounding your tree.

Recently planted trees need more frequent watering compared to established trees until their roots are established. A good comparison is like us as we are young. As an infant, you eat more frequently and as time goes on, the time between feedings will increase. For trees it is similar, you will need to water the tree daily for the first 1-2 weeks after planting. Water every 2-3 days at 3-12 weeks after planting. Finally, after 12 weeks from planting you only need to water the tree weekly. Of course, throughout all these guidelines for newly planted trees you must take account the rainfall the tree is receiving each week.

Finally, watering is essential if you are having a tree treated for an insect or disease problem. We prefer to do trunk injections outside of periods of drought, but that is not always possible as we must meet timing needs to make an effective impact to the pest or disease being targeted. During periods of drought, trees tighten up and limit translocation to conserve water. Thus, if you have an upcoming treatment and rainfall has been scarce, it is important to water your tree actively leading up to the treatment and following the treatment. This will allow the tree to actively translocate and be able to effectively take up the treatment. If watering is not done in advance, the tree will not take up the product as effectively or at all.

Rain will eventually return, but in the interim you need to understand how to best water your trees. Using a hose or sprinkler are both effective methods for watering your trees. When using a hose, put it on a slow trickle for about 15 mins, moving the hose about every 1-2 minutes to different locations throughout the canopy cover (dripline) of the tree. If you use a sprinkler, simply place a small bowl in the area of the sprinkler and once it fills to about an 1” of water then you are done. Both are very effective methods of watering your tree.

There are numerous resources and techniques out there on how best to keep your trees watered during periods of drought or during the establishment process of a newly planted tree. Determine what is best for your tree and enjoy the benefits of a healthy urban forest!

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