Deep Water Your Tree for Deep Roots

Simply stated, encouraging deep root growth is universally accepted as good horticultural technique. Deep roots stabilize our trees and shrubs and the deeper roots can tap water from deeper in the soil where moisture is retained for longer periods of time.  One of the biggest obstacles to developing deep roots is the habit of daily or too frequent watering, where the roots are not encouraged to grow downward for water, partially because they have sufficient moisture they need near the surface and over saturated soil below.

Shallow rooted trees and shrubs may survive normal conditions but when it gets hot out, the surface is the first place to dry out. Even though there is water deeper in the ground, it is not tapped, because their active roots are only on the surface. Shallow daily watering can lead to:

1. Shallow roots that do not provide stability
2. More frequent & wasted watering, because the tree is relying only on the surface roots for sustaining moisture
3. Roots growing under paving looking for oxygen
4. Unhealthy trees & shrubs that are much more susceptible to disease & insect infestations
5. Daily watering encourages weed growth by providing the continuous moisture needed to germinate weeds that would not happen if the soil dried slightly

More importantly, we can kill or reduce the health of our plants and trees by continued saturation of the soil. Plant roots require oxygen for growth and respiration. Devoid of oxygen, plants can literally drown- the roots die and the plant is left to rely only on what surface roots that are still alive if any. The key is to water deeply and infrequently enough that the roots grow downward for the water. Be careful though, if the plants are allowed to dry out too much, the minute root hairs (feeder roots) may die, setting back the process. It is important to understand that it is a process. You cannot just cut back on how often you water; you must slowly train the roots to grow down. Water less and less frequently while increasing the amount of water as the plant matures and/or develops deeper roots. Several short watering periods spaced out across the morning are more efficient in most cases than a single long watering. For instance, instead of utilizing one 12-minute watering period, change to a 3-4–minute watering period with three separate start times cycling shortly after the other.

Encouraging deep root growth is a balancing act that is complicated by many factors, including but not limited to, new landscaping, soil types, existing roots from trees and shrubs, plant types, plant groupings, prior watering techniques, sprinkler systems, shade, sun, slopes, drainage systems, changes in the weather, and numerous other factors. Water penetration also depends on the soil. Sandy soil absorbs water much more quickly than clay soil, and loamy soil falls in the middle. It is thus important to check your soil for absorption.

The benefits of deep watering can also be seen in our lawns in ground covers. The same rules apply and the amount of water savings can be enormous. If you want to learn more, check out our sister article: “Lawns Can Survive On Twice a Week Watering”