Everything You Need To Know About Watering Your Trees

Our trees are incredible organisms – we will do our best to hold back our rave reviews. Since we are dedicated to maintaining, treating, and preserving urban trees, we encourage our community to do the same. One of the most basic – and essential – tasks of tree care falls in the hands of a homeowner: watering.

Facts about Tree Watering Needs

• Most of a tree’s feeder roots are in the top 12″ – 18″ of the soil. Since they are so close to the surface, they are more prone to drying out.
• Typically, trees with small leaves cool off quickly and are more adept at using water efficiently than trees with large leaves. These trees often have a thick waxy coating, thick bark, and expansive root systems.
• Symptoms of drowning and drought look remarkably similar. Both cause yellowing leaves, wilting, drooping, and leaf drop.

Irrigation Systems vs. Direct Soaking

Effective coverage of the entire root ball is only achieved by a deep soaking for infrequent (once a week) intervals. Conversely, irrigation systems dispense shallow and frequent (often 3 times a week) intervals. This method is designed for turf. If an irrigation system is relied upon to water trees, the roots will become desiccated. This is because 1) the topmost tree roots are inches below turf and 2) the water evaporates quickly from the soil surface. Feeder roots deeper than a few inches will die off swiftly. This will result in a poorly anchored plant that is stressed, undernourished, and is limited in its ability to support photosynthesis and other necessary life functions.

How to Check if Your Tree Needs to Be Watered

Here’s the catch – there are no hard and fast rules about watering because every tree is subject to different variables. Watering requirements depend on the type of tree, where it is planted, the type of soil you have, the wind, the temperature, proximity to structures or hardscaping, shared root space, rainfall, or if the tree is in shade or full sun.  Fortunately, your observations will clarify your tree’s individual needs and inform your approach.

First, check the soil around the root ball to determine if the tree needs water. A few inches away from the trunk, dig down into the soil or use a soil probe. This way you can see what the soil looks like a few inches down into the root ball of the tree or shrub.  If the soil is powder dry, you need to water. Another problematic situation is if the soil is completely saturated and muddy, or if it has a foul odor. Let the soil dry out so the roots can regain access to air, checking the soil once a week. Also, monitor the temperature as well as the amount of rainfall with a rain gauge. Balance your approach based on the watering guidelines outlined below.

Watering Methods

If the soil is powdery dry, it repels water in the same way a bone-dry sponge does – this reaction is called hydrophobia. Sprinkle the soil surface until it softens, then proceed to one of the following watering methods.

Hose

This method can be used for newly planted or mature trees. For young trees, place the hose into or on the soil nearest the center of the planting hole. Turn the hose on as if you are going to take a drink from it, like a water fountain. Let it run until the soil will not absorb anymore. If water is running off within the first few minutes, turn the pressure down. You can time the first several watering sessions; it takes between 15 minutes to an hour to completely soak the soil. For mature trees, move the hose around the root zone to soak the soil within the dripline. Occasionally, adjust the amount of watering based on your observations.

Sprinkler

This is not recommended for a few reasons. For one, it is inefficient and costly; a significant amount of the water will evaporate in the hot air and soil surface before it can soak into the soil. Also, overhead watering splashes the soil and foliage, creating the perfect transmission zone for soil-borne diseases and fungi and increasing the risk of infection. Even so, this may be the most practical option for some to make sure their plants are well watered.

Run the sprinkler for at least an hour on one side of the tree. Then move it to the other side of the tree so the water can disperse over the entire spreading root zone. This method is better used on mature trees.

Soaking Systems

Fortunately, some products are designed to make watering targeted and efficient. One product is a slow-release watering bag. The bag loosely surrounds the trunk and can be filled rapidly with a hose. Another product is a soaker hose which is placed over the tree’s root ball. With both products, the permeable material releases the water over several hours, providing a full soaking without any runoff and very minimal moisture loss. These methods are best used for newly planted trees.

Watering Guidelines

• Properly watering newly planted trees at the correct intervals is critical to establishing your new plants and protecting your investment. After planting a new tree, water once per day for the first 2 weeks, 2-3 times per week for the next 3 months, then follow the guidelines below.
• If the soil is dry to the touch, it hasn’t rained recently, and:
  • Temperatures are under 95 degrees: water once per week.
  • Temperatures are over 95 degrees: water once or twice per week; soak deeply to mimic 2 inches of rain.
• To prevent desiccation and winter burn, evergreen plants (boxwoods, arborvitaes, spruces, pines, and hollies) should be watered throughout the winter. Since evergreens keep their foliage during the winter months, they easily lose moisture as the arid air wicks the moisture. Between November – February, water when air temperatures are above 40°.
• Mature trees also need regular watering. Check the soil weekly and water when the soil is dry.
• It is better to water deeply and infrequently rather than shallow and frequently.
• Unestablished trees will need to be watered routinely for the first 2-4 years. More specifically, every inch of truck diameter indicates how many years it will take to become established. For example, a 2-inch trunk diameter tree will take 2 years. A 4-inch trunk diameter tree will take 4 years. In other words, the larger the tree you plant the longer it will take to become established. A good reference for the amount of water needed on a young tree is to multiply the diameter of the trunk by 1.5. This will give you the gallons needed per watering.

If you have any questions about your trees’ specific needs, contact us anytime. If you’d like to delve deeper, here’s some more information about watering your trees.