Roots grow in the path of least resistance. They don’t seek water and they don’t seek fertilizer. They also don’t seek sewer and septic systems. They just grow where it’s easy to grow.
Therefore, if you irrigate shallowly, the roots grow in the area that is damp. They don’t need to grow any deeper. If you irrigate deeply, the roots will grow deeper.
Take a lawn that is irrigated for instance. If the sprinklers are set to run three days a week and only for a short period of time, the roots don’t really have to grow much to get water. You end up with a shallow root system that is dependent on regular watering.
I don’t water the lawn in most cases. Turf type tall fescue is very drought tolerant and tends to stay green through most dry spells.
Kentucky bluegrass, on the other hand, goes dormant when it gets dry. I don’t mind the color of dormancy. On the other hand, Kentucky bluegrass can only take about three weeks without water, so a good soaking is important to keep the crowns saturated.
I spend a lot of time teaching people about watering. Most people think they are giving plenty of water to plants and sometimes they hit the mark. Many don’t give plants sufficient water.
When it comes to hanging baskets and containers, water them until water drains out of the bottom, soaking the entire root system. Again, this encourages a deep root system that withstands dry periods a little longer.
Depending on the size and location of the basket or container, you may even need to water more than once a day.
In terms of newly planted trees and shrubs, how much water is needed? Again, instead of providing a “blessing” with the end of the hose every two or three days, I lay the hose down around the root system and turn it down to a trickle.
Let the water trickle until the soil is saturated throughout the root system. I do this maybe two times a week unless it’s exceptionally hot and dry.
Remember, the new roots haven’t gotten established into the parent soil and are dependent on the water that you supply initially (or rain).
If someone asks how often you water a particular plant, there is no straight up answer. It depends on a lot of factors. The type of soil, the species, the location in the landscape, and your water pressure.
Eventually you get a “feel” for how to water. Ask any greenhouse owner, the person who waters is one of the most important people in the operation.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at firstname.lastname@example.org.