Guide to Tree Watering
Anyone who has planted a tree knows that providing the right amount of water at the right time is a key factor in tree survival. Learning how to determine when your tree needs water and how to apply it is a very important part of tree ownership. Check out our handy guide to watering trees to find out when, where, how, and how much to water your tree at any given time.
What Affects How Much Water a Tree Needs?There are a number of factors that go into determining a tree’s water needs, and maintaining an awareness of these different conditions is the first step in gauging how to properly care for your tree.
- Time of Year – Water needs are greatly reduced during the winter dormancy months. Trees are losing less water at this time through evapotranspiration due to lower temperatures and by shedding their foliage (for deciduous trees).
- Tree Species – Some tree species are more drought tolerant than others. Ongoing water needs can be reduced by selecting a species that is drought/heat tolerant and well adapted to the conditions of the Edmond area.
- Soil – Clay soils typically hold moisture, while sandy soils dry out quickly. Knowing your soil type can help you to adjust how often you provide water for a tree.
- Climate – Temperature, wind, precipitation, and humidity all impact a tree’s water needs at any given time. Trees will need water more often during a hot, windy, dry period than during a cool, rainy time.
- Site Specific Conditions – Shade or full sun? Mulched bed or an open lawn? The “microclimate” that your tree is planted within can also impact its water needs.
ToolsA garden hose is an essential tool for watering trees by hand. When using irrigation systems, drip is preferred - it’s important to note that lawn sprinkler systems generally do not provide the type of deep watering that trees prefer. An irrigation bag can be used with your garden hose to mimic drip irrigation. Place it around the base of the tree and fill with water, which will drain out slowly to maximize absorption by tree roots. These are mainly beneficial for newly planted trees since most of their roots are still near the trunk (see "Where to Water"). For established trees, five gallon buckets with small holes drilled in the bottom can be placed at the appropriate watering location to mimic the same effect.
Mulch is not technically a “watering tool”, but it can help soil to retain the moisture that you apply when watering, among a myriad of other benefits. We recommend spreading a 3-4” thick layer of mulch around your tree within the drip line, pulling it back off the trunk a few inches.
When/How Often to WaterFor all trees, check soil moisture before applying additional water. To do this, dig down a couple of inches in the soil. If the soil is dry, it’s time to water. If it’s still moist, you can wait a little longer. If the soil is soggy, definitely wait--there may be a drainage problem or too much water has already been applied. If at least an inch of rain has fallen in a given week, watering is likely not necessary.
The early morning hours are usually the best time to water, since trees are losing water at a lower rate and overall less evaporation is occurring than later in the day. Here are some more specific recommendations based on stages of a tree’s life:
- Newly planted trees include those within their first couple of years after planting. These trees had limited root systems that were disturbed at planting time and are working hard to establish roots in the soil around them. They need water immediately after planting and anytime soil begins to dry out until establishment (a couple of years after planting). Generally speaking, newly planted trees in Edmond need water about once a week during the growing season and once every other week during the winter months. This may be used as a guideline, but we recommend checking your soil moisture to confirm.
- Newly established trees have been in the ground for a few years now, but they may still struggle during the really hot, dry times of year since they are still expanding their root systems. Rainfall should generally provide adequate moisture, but it’s a good idea to keep an eye on them in late summer/times of drought and throw a little extra water their way if signs of stress such as scorched leaves or defoliation are observed. If you have planted a sensitive species with low drought/heat tolerance, your tree may continue to need supplemental water at this stage (and beyond).
- Mature trees are the more established trees in your yard that have been there for several years already. They are pro’s at managing their water needs in Oklahoma’s conditions… or at least they should be if they are an adapted species—they’ve made it this far! More often than not, mature trees can make do without supplemental water from us. A few instances when a mature tree might need a little extra water include times of extreme drought, following damage from a disturbance such as construction activities (especially when roots are impacted), and compromised condition due to impacts of disease or pests. Mature trees can also become stressed by too frequent watering. It is recommended to wait at least a couple of weeks in between watering events and always check soil moisture. Be extra cautious when dealing with native oak species such as post oak and blackjack oak – they should be very well adapted to Oklahoma’s dry conditions anyway, and we often see overwatering stress in these trees— particularly where it concerns frequent lawn irrigation.
Where to WaterIt’s important to focus watering efforts on the area beneath the furthest reach of the branches, known as the “drip line”. Most of a tree’s absorptive roots are found here, and applying water to this area will encourage outward root growth which is very important for newly planted and newly established trees. For newly planted trees, it’s also a good idea to soak the original root ball area. When watering is required for mature trees, target the area at the drip line as well as just inside and just beyond it.
How to WaterWhen watering with a garden hose, turn it on at a rate that will result in low runoff of water, so that as much as possible will infiltrate into the soil. This may be accomplished by soaking the area with your hose, turning it off until the water drains into the soil, and then soaking it again. When using an irrigation bag, we recommend thoroughly soaking the soil, in addition to filling the bag. For larger trees, turn the garden hose on at a medium pressure and lay it beneath the drip line. As you soak the soil, gradually move the hose around the perimeter of the tree.
How Much to WaterTrees prefer deep watering that moistens the top several inches of soil – the largest concentration of a tree’s absorptive roots is found in the top 12 inches! Trees need roughly 5-10 gallons of water per inch of trunk diameter. It can be challenging to gauge just how much water that is, but you can get a feel for that by timing how long it takes to fill a 5 gallon bucket and then go from there. Check the soil the next day to see how moist it is. If soil is soggy, you may need to back off on the amount of water applied.
As you grow accustomed to your yard’s conditions and patterns that arise in your watering practices throughout different times of year, determining your trees' water needs will become easier. We hope that this guide will lay a foundation for starting you on your way!
View other topics from the Spring 2018 issue of Edmond Tree Mail.
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