By: Jeffrey P. Hagfors, Certified Arborist WI-0181A
All trees respond to their growing environments. Their long-term health is influenced by changes in availability of soil moisture; condition of the soil; availability of nutrients, and pressures from insect and disease. Birch trees are one of the most sensitive trees in our urban forest, and respond unfavorably to the urban environment. Native stands of birch trees are found in cool, moist sites with good soil drainage. When planted in our yards, the hot summer sun warms the ground under the tree and can overheat the soil. Western and southern exposures can be especially difficult locations to grow birch trees. Additionally, the turf grasses in the urban environment will greedily outcompete the birch for nutrients and water. Without proper care, urban birch trees will not grow to their fullest potential.
Proper care for your birch trees begins with proper watering. During the summer months, established birch trees require one inch of water per week, whether this moisture falls from the clouds or from your sprinkler. Always check before irrigating. Stick your fingers into the soil. If you can roll or form the soil into a ribbon or ball, soil moisture is adequate. Too much water can be harmful to birch trees also.
Proper use of natural, organic mulch is another key essential for the long-term health of birch trees. Maintain a generous bed of mulch under your birch tree. Keep it at a depth of 2-3 inches, being careful not to pile it against the trunk. Mulch has multiple benefits. As mulch decomposes, it builds organic material in the soil, which in turn, rebuilds soil structure, improves its nutrient holding capacity, and increases soil aeration. Proper mulching preserves soil moisture, increases rooting, moderates temperature extremes and protects the thin bark of birch trees from damage caused by lawn mowers and string-trimmers. Help your birch even more by planting low-growing shrubs and perennials in the mulch under the canopy (away from the trunks) to help shade the root system. Avoid using weed barriers and landscape fabrics under the mulch as they will only reduce the benefits of the mulch.
Regular fertilization of birch trees is important to maintaining their health. Maintaining proper nutrient levels promotes plant vigor, the first line of defense against the pressures of insects and disease. Many birch trees respond to low fertility with small, stunted leaves, reduced growth and increased susceptibility to insect and disease attacks. Additionally, chlorosis, the yellowing of leaves, indicates a lack of one or more of the micro-nutrients that birch trees need to maintain a high level of vigor.
Birch trees need to be protected from insect attacks. The bronze birch borer will quickly take advantage of a white birch that is in less-than-perfect health. Too little or too much water, poor soil conditions, low vigor and damage from leafeating insects will predispose a white birch to bronze birch borer attack. Annual soil injections of an insecticide containing Imidacloprid will deter the entry of bronze birch borer. If bronze birch borer is already in the tree, a trunk injection of Bidrin insecticide may be needed to eliminate them.
Birch trees are common in the landscape, but caring for them is anything but routine. Each individual is different. Trust the individual care and treatment of your birch trees to your experienced Wachtel Certified Arborists.
© Copyright 2008 – Wachtel Tree Science & Service, Inc.