By: Tim Daly | Gwinnett County Extension Agent
Tim Daly

Fall is an excellent time of the year to install trees and shrubs. During the cold weather months, the top part of the plants grow very slowly, but the roots will continue to grow and expand. By the next growing season, they are better established and can tolerate the hot, dry conditions of the summer.

Unfortunately, landscape plants are installed in places where they will outgrow the space and into other plants as well as structures. Plants should fill the space, not compete for it. Knowing the mature size of what you are planting will help reduce the likelihood of having these types of troubles.

After planting, most plants will increase in size over time. Some species grow at a faster rate than others; some will ultimately be larger than others. If they are not spaced properly, the plants will begin to crowd each other resulting in increased competition for water, nutrients, light, and space. Plants with a more vigorous growth habit will overtake the others. Other detriments are increased disease and insect activity due to lack of airflow, higher moisture levels amongst the plants, and weaker plants.

A common species harmed by improper spacing is the Leyland cypress tree. They have the potential to grow 60 feet tall and 15 to 20 feet in width. This fact is rarely taken into account when they are planted. They are popular because homeowners desire a fast growing plant that will provide a screen for privacy. If planted too close together, they will grow into each other. They are also at increased risk for certain fungal canker diseases, which cause branches to start turning brown and dying. In a row of Leyland cypress, often one or more of the trees can be observed dead or dying. If spaced apart properly, the chances of these issues occurring are reduced.

Frequently trees under power lines are pruned harshly to keep them from growing into the lines. This heavy pruning, also known as topping, severely harms the tree. Smaller growing trees or shrubs need to be planted in these locations. Homeowners need to learn how large their landscape plants will be when they reach maturity. For example, let us say a homeowner plants a southern magnolia, which can ultimately grow to 40 to 60 feet in height. However, they want the tree to grow no more than 10 to 20 feet tall. They mistakenly believe that constant pruning will keep it at the desired height. The problem is this species naturally grows much taller. Regular pruning to keep it at this height will be detrimental and cause it to have a poor appearance. Instead, the homeowner should plant a smaller tree such as a Japanese maple, Chinese fringe tree, or dogwood.

With trees, take into consideration how the ultimate size can affect the condition of your home. If planted too close to the foundation, individual species of trees could cause damage. As tree increase in size, their roots could start uplifting, and damage concrete surfaces of driveways and sidewalks as well as possibly harm the foundation. Also, they are at increased risk of being blown over in storms.

Remember, knowing the size of landscape plants can reduce the likelihood of problems as well as create an attractive, healthy landscape. For more information on how large various ornamental plants will grow along with other pertinent in-formation, refer to the Extension publication Landscape Plants for Georgia which can be accessed at the following website: http://extension.uga.edu/publications/detail.html?number=B625.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with UGA Extension Gwinnett. He can be contacted at 678-377-4011or tdaly@uga.edu