NOBLETON AND KING CITY HORTICULTURAL SOCIETY

Trees have been referred to as the lungs of our planet. They filter out toxins in the air. They generate oxygen during photosynthesis and store carbon. They are prized in our landscape for their ability to block out views, act as a sound buffers, and elevate our property’s resale value. Properly positioned in our gardens, they can actually help to reduce utility costs. Trees also provide habitats and food for songbirds, small mammals and beneficial insects. Their canopies shield the soil surface from hot sun and blowing winds. Their roots also help to keep the soil in place preventing erosion.

In order to have the benefit of a healthy tree above the ground we should understand the needs of the tree below the ground.

There is a complex system of roots all doing their best to contribute to the tree’s well-being. They search out oxygen, water and sources of nutrients.

Tree roots develop and survive where there is adequate oxygen and moisture. The most active tree roots are in the top 3 feet of the soil; the majority being in the top 12 inches. The more compacted or poorly drained the soil, the closer the roots are to the soil surface. Roots will grow most of the year, stopping only when the soil temperatures are cold.

Trees develop two types of roots. The woody roots become thicker each year and grow downwards as well as outwards to help anchor the tree in the ground. The absorbing roots fan out horizontally taking up water and nutrients and are replaced annually. Roots normally grow outward to about three times the branch spread.

Most trees do not have a deep tap root. Trees have developed a symbiotic relationship with a fungi known as michorizza. This fungi aids in drought tolerance for the tree by attaching itself to its root system. It is able to quickly travel underground to areas that the tree roots may not be able to reach. Michorizza absorbs water and nutrients and feeds the tree through the roots. As with compost, it has been found that when michorizza is present there is noticeably less soil born diseases. It also aids in protecting the tree against root rot. Scientific studies have estimated that 20% of the tree’s carbohydrates may go to feed michorizza fungi. In return, the fungi provides the tree with 700 times more nutrient absorbing surfaces.

Earthworms are your best friends. They can dig down into the earth 10 – 15 feet. These channels break a path for the trees’ root system to grow and the castings from the earthworm bring phosphorus closer to the roots for absorption.

Adding organic matter (compost) will help to maintain the moisture in the soil, but it will also change the Ph level. It surrounds sand particles and helps fertilizers to attach more readily rather than simply draining away. Each year your tree will replace and loose 80% of its absorbing roots adding to the organic matter. Careful aerating around your trees will help to increase the amount of oxygen getting to the roots.

When using mulch to protect your tree roots try not to distribute it too thickly since it will keep the roots too cool and prevent growth. If your mulch is placed too thinly, it will dry out and leave the roots unprotected against the heat and drought.