Eucalyptus, often called gum trees, are popular among home gardeners globally due to their distinct aromatic foliage and fast-growing nature. These Australian natives quickly establish themselves, offering ornamental appeal and attractive, often silvery-blue, leaves. Understanding the proper planting and care techniques is important for the health and longevity of these unique trees. This guide provides a step-by-step approach to successfully planting and growing a eucalyptus tree.
Site Selection and Preparation
The long-term success of a eucalyptus tree begins with selecting the correct planting location, which must accommodate the tree’s eventual size and environmental needs. The first consideration is hardiness; these trees are generally suited for USDA zones 8 to 11, though specific species like Eucalyptus gunnii exhibit greater cold tolerance. Matching the species to your local climate is the most important pre-planting decision, as not all varieties are equally adaptable.
Eucalyptus requires a location that provides full sun exposure throughout the day to ensure optimal growth and foliage color. They thrive when receiving at least six to eight hours of direct sunlight daily. A well-drained soil structure is also important, as the trees are susceptible to root rot in waterlogged conditions, often described as “wet feet.”
While they tolerate a variety of soil compositions, most species prefer a slightly acidic to neutral pH range (5.5 to 7.0). Improving heavy clay or poor-quality soil by incorporating organic matter like compost can enhance drainage and aeration before planting. However, excessive fertilization or rich soil is unnecessary and can increase their susceptibility to pests, so a moderately fertile setting is preferred.
The Transplanting Process
The physical act of planting a eucalyptus sapling requires careful handling, as the root systems are sensitive to disturbance. The best time for planting is typically in the spring or early fall, allowing the tree to establish its root system before extreme weather conditions arrive. Begin by digging a planting hole that is two to three times wider than the root ball, but not significantly deeper.
The goal is to create a wide area of loosened soil that encourages lateral root growth, keeping the root collar—the point where the trunk meets the roots—at or slightly above the surrounding ground level. Eucalyptus are prone to becoming pot-bound, but caution must be used when addressing a tightly coiled root ball. Unlike many other trees, some sources advise against aggressively loosening or scoring the root ball, as this can be fatal to the delicate roots.
Gently place the tree into the center of the hole, ensuring it stands straight before backfilling with the removed native soil. As you refill the hole, lightly tamp the soil to eliminate large air pockets, which can dry out the roots. Do not bury the root collar, as covering this area can lead to bark issues and root rot.
Immediate Establishment Care
Once the eucalyptus tree is in the ground, providing immediate and consistent care helps the plant recover from transplant shock. The newly planted tree requires a deep initial watering to settle the soil around the roots and eliminate any remaining air pockets. This first watering establishes good soil contact.
For the first few months, a regular watering schedule is necessary until the roots extend into the surrounding soil. A deep watering once or twice a week, depending on local weather and soil conditions, is more beneficial than frequent, shallow watering. This encourages the roots to grow downward, leading to a more drought-tolerant tree.
Applying a layer of organic mulch, such as wood chips or shredded bark, around the planting area helps conserve soil moisture and suppress weeds. The mulch layer should be maintained a few inches thick, but keep the material several inches away from the trunk to prevent moisture buildup that can cause bark rot. In areas prone to strong winds, temporary staking using soft ties and an H-section support structure can prevent “root rock,” which occurs when the wind moves the trunk and damages the fine roots.
Long-Term Growth Management
Eucalyptus trees are renowned for their vigor, and managing their size and shape is often the primary focus of long-term care. Once established, mature trees are drought-tolerant and require significantly less supplemental watering, benefiting most from deep irrigation only during extended dry periods. Avoid applying general fertilizers to established trees, as this can encourage excessive soft growth that is more attractive to pests.
For size control, home gardeners often employ specialized pruning techniques, such as coppicing or pollarding. Coppicing involves cutting the tree back severely to near ground level (typically 4 to 18 inches) to stimulate the growth of multiple new stems and retain the attractive juvenile foliage. Pollarding is a similar method that involves cutting back branches to a permanent framework (usually 6 to 10 feet above the ground) to control height and encourage a dense canopy.
Routine structural pruning helps develop a strong framework in younger trees by removing lower side branches and shortening remaining side shoots. This formative pruning is best done in late winter or early spring before the period of active growth. Monitoring for pests, especially the Eucalyptus psyllid, is a necessary part of management, as water-stressed trees are more susceptible to these sap-sucking insects.