Too much moisture can hinder root development

COLUMBIA, Mo. – It might sound bizarre, but all the rain many parts of Missouri got this year has primed plants, trees and shrubs for the possibility of drought damage.

Roots are the lifeline of a plant, taking up water and nutrients from the soil and moving them into the leaves, where they can interact with sunlight to produce energy for the plant. A robust root system is the foundation of a healthy, vigorous plant.

“The roots of plants need oxygen to respire just like you and I need oxygen,” said David Trinklein, horticulture state specialist for University of Missouri Extension. “When it rains a lot, the pores in the soil that had contained oxygen are filled with water. Thus, the roots become oxygen-deprived, at times to the point of death,” he said. Even if roots survive, prolonged waterlogging or lack of oxygen tends to stress roots and make them more susceptible to root rots and anaerobic pathogens.

For most plants, including woody plants such as trees and shrubs, the deepest roots will succumb first to waterlogged soil and only the shallow roots survive. This is because there is more oxygen toward the surface of the soil.

Plants gardeners established this past spring face the same problem. They haven’t sent their roots deep into the soil because they have not been forced to do so. The top several inches of soil have been a haven for roots, containing all the water and air they needed, Trinklein said.

Here’s the problem: When the rains subside and temperatures soar, the water in the top layer of the soil disappears very quickly. This can result in drought injury even though yearly rainfall totals have been above average.

“It is best to water thoroughly but infrequently,” Trinklein said. “This will encourage roots to follow the water to the lower profile of the soil. It also will promote the development of deep root systems, which plants need to stay healthy.”

Trinklein says here’s a long-term solution to help your plants when conditions are too wet or too dry. Working well-decomposed organic matter into the soil will help build soil structure that will let water easily percolate into the soil. Organic matter also creates large soil pores filled with oxygen-laden air.

For more gardening tips, visit your local MU Extension center or go to explore horticulture and gardening on the MU Extension website.