How, When, and Why To Water Trees Effectively

By Richard Flowers, ACCNP-Green Thumb Nursery-Ventura

Why water trees?

Trees are a precious resources for our communities we live in. They filter the air of toxins and help to bind the soil to mitigate erosion. Trees absorb dust, wind, and reduce glare. They can cool an area by up to 10°F, by shading our homes and streets, breaking up urban “heat islands”, and reducing energy costs. Many species are bird and wildlife sanctuaries, provide edible food, and have beautiful flowers. These organisms can be used for windbreaks, privacy, and some even have great historic and sentimental value. Having trees makes the community more homey, increases property values, and improves the quality of life for people around them. This is why it is critical to preserve these semi-permanent living treasures in our own landscapes by watering them effectively. Below I will provide timely tips and suggestions on how, when, and where to water these wonderful plants called trees.

 How does being more efficient with water result in healthier trees?

When a tree is watered in an efficient manner the result will be a healthier and more vigorous plant. When a tree is not irrigated properly it will become weaker and be more susceptible to stresses like insects and diseases resulting in poor growth and a sickly appearance especially in times of drought. It is important to water deeper and longer to establish deeper roots giving the tree more anchorage in the soil and the tree will become more drought tolerant. A tree with roots showing on the ground is weaker and will not prosper. Plant roots always grow where there is water, therefore it is wise to water longer, deeper, and less frequently. Below are some helpful ways to water your trees.

How to water?

Most times, watering deeply involves having a slow or low volume of water over a longer period of time. The goal when watering your trees is to provide good thorough soakings (not a light spray) where the water seeps into the soil 1 to 2 feet because this is where most of the tree roots are. Below are some simple methods to accomplish this.

  • Bucket Method 1

Take a 5 gallon bucket and fill it up all the way with water. Simply pour the water slowly filling up the water well or watering basin around the tree, having the soil soak up the water, and repeat the procedure until the bucket is empty.

  • What is a watering basin?

A watering basin is simply a berm of soil around the root ball where water is applied to.

  •  Bucket Method 2

Drill small holes in the bottom of the 5 gallon bucket then fill the bucket with water. Place the bucket where the tree is as stated in method 1, the water will slowly trickle out of the holes watering your tree slowly.

  •  Soaker Hose Method

This is my favorite method of deep watering. Simply spiral the soaker hose from the drip line inward 2 to 3 times.Turn the hose on and the water will seep out slowly for several hours. Make sure you have a pressure regulator connected to the hose faucet and soaker hose because this special type of hose runs on lower pressure.

  •  Garden Hose Method

Stretch the garden hose to where your trees watering basin is, then turn the faucet on very low to water your tree for several hours. The idea is to fill up the watering basin, turn off the water, then let water trickle into the soil, when that is complete repeat one more time.

  • Hose Sprinkler Method

Easily attach a hose sprinkler to the garden hose and place the hose sprinkler near the tree, turn on the water for the proper amount of time.

Where and how much to water?

With a new planting of a tree and until  several months old, water close to the trunk but not at the trunk. Be sure to have a watering basin or well and apply the water to that area.

Established trees (trees that have been growing in the landscape after several months to over a year old or more) water where drip line or canopy of the tree is.

What is the drip line?

The drip line, drip zone or canopy of the tree is where all the branches and leaves extend out. This is where the delicate feeder roots are what bring up water and nutrients necessary for plant growth. It is critical to water your trees at or just beyond the drip line.

A good rule of thumb for how much to water your established tree is 80 -100 gallons. Generally speaking, when you water by way of the bucket method you can divide the area under the drip line into four equal sections like a clock:  12 o’clock, 3 o’clock, 6, and 9 o’clock. Each area you apply 20 gallons of water. Simply fill the 5 gallon bucket 4 times to equal 20 gallons.

When using the hose sprinkler method the goal is to water 2 inches at each designated sections as detailed  above. To determine if the hose sprinkler (or any sprinkler: manual or automatic) have reached 2 inches, simply use a cup and with a ruler mark with a permanent marker 2 inches. Turn on the sprinkler on low and write down the time it takes to fill up 2 inches. This is how long you need to run your sprinkler for at each section. Generally speaking, each section should take about 2 hours watering slowly and deep.

When using a soaker hose, the watering is usually accomplished in 6-8 hours.

When should I water?

In most cases, established trees usually need watering 1 or 2 times per month or more often in extreme heat or if rains are not sufficient.

When watering new trees, weekly irrigation would suffice.

Your watering depends on conditions. Conditions such as temperature, location, time of day, humidity, wind, time of year, soil, stage of growth, terrain, microclimates, and exposure all play a vital role in influencing when you need to water. I will break these down for you and provide you some examples:

  • When it is hot, low humidity, and windy plants demand more water, therefore it is necessary to apply water and oftentimes more frequently.
  • When conditions are cool, not windy, cloudy, and higher humidity your trees demand less water, less often.
  • During the summer, trees always demand more water, while usually during the winter many trees don’t require as much water. If you have a tree that loses all its leaves during the wintertime, that is a resting period and the tree does not need additional water in most cases.
  • Anytime when the weather changes your watering habits need to change.
  • Where you live greatly determines when you need to water. If you live in a cooler coastal area, these areas need far less water than locales that are in hot inland climates.
  • The same watering practices does not apply to all areas of the landscape. Examine your own landscape and determine if there are areas where hot air settles or on the southwest side of the property, next to a hot wall or driveway, on the top of a slope, and extreme sun exposure because these areas dry out quicker and need water more frequently. Additionally, your own garden may have areas where cooler air settles, in the shade, on the north or east side or on the bottom of a slope these areas stay moister longer and do not need as much water. It is also important to examine your yard each season as the sun and season change.
  • The type of soil you have has a bearing on when you water. Sandy soils tend to drain quickly and therefore these soils need more frequent irrigations at shorter periods of time. If your soil happens to have clay, then these soils typically dry out more slowly, are harder to wet, and require longer watering cycles.
  • The most important tool you need to determine when you need to water is a bamboo stake, screwdriver or other such probe. Simply stick the screwdriver into the soil 6-8 inches. If the probe goes in easily, the soil sticks to it, and is moist the soil is not ready to be watered at that time. If the probe will not go into the soil with ease or when you stick it in and pull it out and shows that it is dry, there is a need to water. It is wise to do this practice in various places where the tree needs to be watered. These devices are also useful to indicate how far water has gone into the soil after you water.
  • The best times to water is when the temperature is lower, less windy, and higher relative humidity. Usually this is accomplished in the early morning and late evening.

Please be advised the above information is only a guide, different species of trees have varying water needs depending on where they are growing. It is always advisable to physically check soil moisture with a probe instead of using set watering intervals or relying upon automatic timers.

 

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