Deep Root Watering

Deep Root Watering

Deep Root winter watering for trees and shrubs

Do your evergreen trees turn brown?

If the needles of your pines, spruce or other evergreens are turning brown, yellow or orange, they probably need more water.

Few people realize though that we tend to over water trees in the summer, and underwater in the winter.

Evergreen trees and shrubs never really go dormant, and still need water throughout winter. In Fort Collins often have long periods of dry, warm and windy weather, and that can cause drought stress for our evergreens that can continue well into the following seasons.

Do my trees need extra water?

Evergreens that do need extra water in the fall and winter:


White Pine


Spruce & Fir

All evergreens in especially dry years

Evergreens that usually don’t need extra water in the fall and winter:

Ponderosa Pine

Pinion Pine

Rocky Mountain Juniper

Eastern Red Cedar

What’s the best way to water trees?

Although a sprinkler or hose drench works fine, the deep root watering method is a more efficient way of delivering water to a tree’s roots because it forces the soil to become saturated with water, whereas otherwise our heavy clay soil can actually repel water and cause it to run off and evaporate.

The equipment I use pumps water 4″ to 6″ into the ground at 250 psi. An added bonus of this deep root technique is that it lifts and aerates the soil as well.

Do I have to water my trees myself?

Nope: I’d be happy to do it for you! OK, so you could stand out there with a hose and do it yourself, but why would you want to? I have reasonable rates and also schedule watering for the driest times throughout the winter, so you don’t have to worry about anything.

Get in touch for a free Deep Root Watering estimate!
Sometimes trees, like this maple, need more water in the summer too!

How much water do my trees need?

That’s a good question! There are different ways of answering the question. Probably the easiest answer is:

Water when the ground is dry. Letting the ground dry out well, and then watering until it’s saturated in the top two to three inches of soil is the simplest way of watering your trees and shrubs. A well adjusted sprinkler system will do this for you in the summer, but in the winter it’s up to you and I to occasionally water as needed, especially for out evergreens.

There are slightly more scientific ways of watering though, and for high value trees and shrubs the following formula may give better results.

Let’s say you have an Arborvitae and we’re concerned it’s not getting enough water. Now that plant is originally native to the northern Great Lakes region where the lowest average rainfall is about 30 inches per year. In the Fort Collins area, we only get roughly 18 inches of precipitation, so we would need to supplement our arborvitae with at least 12 inches of extra water over the course of a year. That averages to 1 inch per month in extra water in addition to our rain, or about 2.5 inches in total.

In the summer you can put a coffee can out in the yard and see how many inches your sprinkler system puts out per cycle. Let’s say you collect a quarter inch and your system runs twice a week. That would add up to about 2.25 inches of water per month, which should be enough for your arborvitae as long as rain makes up the .25 inch defecit.

OK, now let’s take that 1 inch and turn it into gallons since in the winter our sprinklers are off and gallons can be measured out of a hose.

Generally a tree or shrub’s roots extend out about as far as the plant is tall. So if we have a five foot arborvitae, it has a root area of 3,600 inches (78.5 feet) using the formula to find area. That area needs 1 inch of supplemental water, so:
tree watering formula
Area = Pi × r²

Area (in²) = 3.14 x 60² (supstitute 60 for the height of your plant in inches)

Area (in²) = 3.14 x 3,600 = 11,304

11,304 in² x 1 = 11304 in³. (subsistute 1 for the inches of extra precipation your plant needs)

11,304 in³ divided by 231 (231 cubic inches makes a gallon of water) is 48.9 gallons.

Our five foot arborvitae needs about 49 gallons of extra water per month throughout the year, which makes it a very thirsty plant.

You can turn gallons into minutes of running a hose by timing how long it takes your hose to fill a five gallon bucket. I find it takes about 30 seconds usually, or a minute for ten gallons. That means you would have to put your hose on your arborvitae for a total of five minutes every month to give it the extra water it needs.

That’s not so much by itself, but multiplied by many more plants per property, times many more properties in Fort Collins and we begin to see why low water landscaping is so important.

This is still just a rough guide though. We still have to take into consideration how much sun the plant gets, wether it’s grown in mulch, rocks or lawn, and other factors such as wind. Also, plants do have some ability to adapt to their environment and make do with less water. They do this by closing their stomata which reduces evaporation; although the side effect of this is often limited growth.

In fact the site a plant is grown in is so important that even native Colorado plants like the Colorado Spruce need extra water when grown in an open site. In the mountains spruce and fir grow on the less sunny slopes, and almost never in fully exposed areas. So when we plant a spruce in the middle of a yard, that’s not really it’s preferred environment, and it will often experience some drought stress. Pines on the other hand are better suited to an open, full sun setting.