Extension

Although mostly hidden from view, roots are the key to a tree’s good health. Having a broad understanding of roots can help gardeners make wise decisions about watering, fertilizing and mulching.

Roots can be a mystery, often leading to myths and misconceptions; however, scientists have been studying plant roots for a long time. It’s time to bust some of these myths to help ensure gardeners take proper care of their trees.

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 where there is clay soil 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 taproots. 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.

Here are a few simple practices gardeners can employ to help keep trees healthy:

• Avoid excessive mowing, vehicle parking or other activities beneath trees that can compact the soil.
• Apply fertilizer at least 2 feet away from the trunk and spread it across the area beneath and beyond the drip line.
• Avoid putting mulch within 6 to 12 inches of the trunk.
• Water slowly and thoroughly, allowing the soil to dry slightly between watering.
• Focus on watering the root zone rather than directly at the tree trunk.