While they’re mostly hidden from view and don’t typically add much visual interest in the landscape, roots are the key to good tree health. Understanding the importance of roots will give gardeners a head start in making good decisions about watering, fertilizing, mulching and overall tree care because trees are often the focal point in the landscape.
Because they’re not highly visible, roots often remain a mystery, said David Hillock, Oklahoma State University Extension consumer horticulturist.
“Due to their obscurity, there are lots of myths and misconceptions about roots,” he said. “Fortunately, scientific research about roots goes back to the late 1720s. This information helps gardeners understand the importance of proper root care and helps clear up and bust those myths.”
- Myth 1: Tree roots are only as wide as the canopy or dripline of the tree. Actually, roots often extend well beyond the dripline. In fact, depending on soil conditions, roots may spread up to three times as wide as the canopy. In shallow soil with clay just a few inches down, the roots may reach an area five times wider than the canopy.
- Myth 2: Taproots anchor all trees. Not all trees develop a taproot, which is a large, thick main root that grows directly downward into the soil. While pecan, walnut, some pine and some oak trees develop a deep vertical taproot, most other trees grow a fibrous root system within the upper 2 feet of soil. These shallow roots are responsible for taking up much of the tree’s water and nutrients.
- Myth 3: Trees feed deep in the soil. Trees do have some deep roots, but those are primarily for anchorage/stability, storage and for finding emergency water and nutrients in extreme droughts. The upper couple of feet of soil is more aerobic, where the natural soil processes release the most nutrients. The top foot typically maintains the highest percentage of mineral uptake and water absorption.
- Myth 4: Deep watering is best. Deep watering doesn’t mean soaking the soil several feet deep. Gardeners should water slowly and deeply enough to moisten the top 1 to 2 feet of soil, but avoid keeping the soil saturated. Overwatering can damage the tiny root hairs that absorb water and nutrients.
- Myth 5: Roots sense water and fertility. Roots aren’t psychic, but rather opportunistic. They’ll grow randomly in several directions when conditions are favorable. That’s why concentrating water and fertilizer right around the trunk isn’t a good idea. Instead, spread water and nutrients over a wider area where the roots are growing. Soon they’ll develop more root hairs.
Hillock cautions homeowners to be careful when mowing and weed-eating around trees and shrubs.
“Be careful not to damage roots with mowers or weed eaters,” he said. “Those damaged spots can be an invitation to disease and insect damage, which can affect overall tree health for years to come. Damage to the roots can reduce growth and increase branch dieback. Trees are a big investment, so proper care is vital.”
OSU Extension offers more gardening information online.