Drag out the hose, it’s time to water!

It is recommended that a tree be given 10 gallons of water for each diameter inch of tree trunk. To figure out how many gallons of water your tree might need, measure the trunk’s circumference and calculate the diameter. Tip: go to onlineconversion.com, which will calculate the diameter for you.

Although we’ve had a pretty wet winter by Grand Valley standards, it doesn’t excuse us from giving our trees and shrubs a drink of water. Now that the snow is all gone, and the tulips are poking their little leaves out of the soil, it’s time to give a little TLC to the bigger plants in our yards.

Believe it or not, the crackly brown burnt-looking edge on tree and shrub leaves, which happens later in the summertime, starts with a lack of water in the winter. Watering your trees and shrubs now will help prevent this problem, called “leaf scorch.” Drought stress on trees also leaves them more susceptible to insect damage and disease, and a healthy tree is much more likely to be less of a target for those things.

While newly-planted trees and shrubs are more susceptible to damage from lack of watering during the winter, established landscaping benefits from a drink of water too. Different types of trees and shrubs require more or less water, and if you have a xeriscaped yard, this probably doesn’t matter as much as it does for those of us with non-native landscaping.

I have a weeping birch tree in the front yard, which came with the house. I probably would not have selected this variety of tree to plant in our high-desert environment, since it has such a shallow root system and it needs a lot more water than Mother Nature provides around here. It’s also located on the southwest side of our property, exacerbating the low-water problem because it gets sun all the time.

Doing this correctly takes time and patience. You want to choose a warm afternoon and finish before it gets dark. Chances are, you don’t want to turn on your sprinklers (for fear of having to re-winterize them), and nobody has access to irrigation water yet. This means we’re back to hose-dragging. An alternative would be to drill holes in the bottoms of some 10-gallon buckets, position them around the edge of the root zone and let them slowly drain out.

According to Colorado State University Extension, the best way to water trees is slowly, when the temperatures are above freezing — you don’t want to create a skating rink in your yard. The goal here is to water deeply and patiently, so the water really soaks in a foot below the surface. You could use a soaker hose or a frog-eye sprinkler to do this, or just turn your hose on slowly and place it at the edge of the root zone.

Many times I’ve seen people water their trees by putting the hose right up against the trunk. This isn’t going to help you much, since the fine root hairs that need the water are actually located out below the treeline. To find this, look up and see where your tree’s branches end. Picture your tree with a mirror image of the roots below the soil, reflecting the length of the branches. The roots of most trees reach out to the edge of those branches, below the soil. That’s where you should be watering. Be aware, some of the roots may actually reach into your neighbor’s yard, depending on how close your trees are planted to the property line and how large your trees are.

How much do you water? Shrubs are easier to calculate. Plan on five gallons of water per month for small established shrubs, and five gallons twice a month for small shrubs planted there less than a year. Big shrubs need approximately 18 gallons of water per month, according to CSU.

Regarding trees, CSU recommends the rule of applying 10 gallons of water for each diameter inch of the tree trunk. How do you measure this? Remember back to high school geometry, diameter is the measurement across a circle. I admit to estimating a bit on this measurement in the past because I don’t readily remember the formula for figuring diameter given the circumference of a circle. Luckily, there are online conversion sites that do it FOR YOU! One is onlineconversion.com.

So, my birch tree trunk has a circumference of about 39 inches. That means the diameter of the trunk is about 12.4 inches (according to that super-smart online calculator). So, I’ll need roughly 120 gallons of water for that tree this month.

Apart from getting 12, 10-gallon buckets together and putting them all around the tree, how will I know when I’ve watered the tree 120 gallons? Well, I use one bucket and a hose. I time how long it takes for the hose, running slowly, to fill up that 10-gallon bucket. Then I place the hose at the edge of the root zone and let it run for the same amount of time it took to fill up the bucket. For this tree, I would then move the hose around the root zone to 12 different spots (like a clock, with the tree as the center of the clock). But you could customize this method for any tree.

Does this take a while? Yes. Plan an afternoon around it. Bake some bread. Watch some Netflix. Clean your house or something. But it is important and it does matter.

One more thing: Don’t forget to drain the water from the hose and disconnect it from your faucet. And look forward to beautiful, healthy trees when the heat of summer arrives.

Erin McIntyre is an advanced master gardener, writer and Grand Valley native. Please email her at .(JavaScript must be enabled to view this email address) with story ideas or feedback.


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