Trees & Shrubs: How to Maintain

Learning how to properly maintain your trees and shrubs can make the difference between a healthy, successful landscape and one that struggles on the verge of extinction. Selecting the right plant in the first place will make this job much easier, but some times we inherit gardens whose creators, although well intentioned, planted without respect for the plants’ own needs. We may not be able to correct all of an existing landscape’s problems without some ripping out and replanting, but, by following some simple rules for correct maintenance, we can begin to develop our gardens to their fullest potential.

Pruning Trees

Large, shade trees should be pruned in the winter during their dormancy. These trees should not require pruning often if they are healthy; however, you may occasionally have to remove a large limb that is dead, diseased or otherwise damaged. This can be a daunting task – we recommend hiring a professional arborist if the limb is overly large. If you decide that you can manage, follow these three steps to keep both yourself and your tree in the best shape. First, cut halfway through the branch at approximately six inches from the trunk (start at the bottom and work your way up) (See diagram below, Step A). Next, move out another six inches from the tree trunk and make a complete cut through the branch from top to bottom (Step B). Finally, remove the excess by cutting just outside of the branch collar (the slight bulge where the branch meets the trunk) (Step C). Cutting into the branch collar itself will impede the natural healing processes of the tree.

Pruning Trees

Newly planted trees may be pruned at the time of planting to remove any overlapping limbs or “suckers” (sprouts growing from the base of the tree due to stress).

Avoid pruning late in the summer or fall; doing so may stimulate the tree to produce tender, new growth that will be susceptible to frost damage.

Pruning Shrubs

Thinning, severe renewal and heading back are all effective pruning techniques for controlling the size of a shrub. Thinning is the process of removing select branches at their base. Heading back a shrub is cutting all of its branches to the same height in order to stimulate a new flush of growth at that point (See diagram below). Severe renewal pruning is cutting all of the branches back almost to the ground in order to cause dormant buds at the plant’s base to flush. Some shrubs such as juniper and boxwood will not recover from such drastic treatment; prune these by thinning or heading back.

Pruning Shrubs

The best time to prune evergreen shrubs such as boxwoods or hollies is late in the winter just before they begin to flush new spring growth. (It is fine to prune throughout the dormant season; late pruning just lessens the time that your plant has that stubby, “just cut” look.) If you are too busy to prune in February, you can prune these shrubs throughout the growing season until mid- August, but doing so may stunt the new growth.

Flowering shrubs require a little more attention to timing. Plants that bloom in the spring typically do so from buds that developed at the end of the previous summer or fall. In order to avoid removing buds, wait to prune these shrubs until just after they finish blooming. Summer-flowering shrubs should be pruned late in the winter, just before they begin to flush new spring growth. Because these shrubs usually bloom on new wood, pruning this early should not put your summer blooms at risk.

Avoid pruning late in the summer or fall; doing so may stimulate the shrub to produce tender, new growth that will be susceptible to frost damage.

Fertilizing Trees

Fertilize your large, deciduous or evergreen shade trees around the beginning of February with a granular fertilizer. The area of most active root growth is at the tree’s drip line (the area under the perimeter of the canopy of the tree). Distribute the fertilizer evenly through this area at a rate of 1 pound per inch of circumference of the trunk at a height of 3 feet. Your larger, established trees should require fertilization only once yearly. The fertilizer will move slowly through these trees’ developed root systems and bodies; by the time it reaches the branches, the new growth should be safe from damage due to frost.

A young or newly planted tree requires fertilization at a lower rate of one teaspoon of granular fertilizer per foot of height until it establishes itself in the landscape (approximately 3 years). Fertilize these smaller trees late in the winter, just before new spring growth begins to push out, or as needed throughout the growing season.

Do not fertilize in the late summer or fall. Fertilizer causes the tree to push out a flush of tender, new growth, which will be more susceptible to frost damage and die back.

For specific fertilizer recommendations, please contact your local county extension agent.

Fertilizing Shrubs

Fertilize evergreen shrubs like hollies and boxwoods in early spring, just as new growth begins to push out, or throughout the growing season as needed at a rate of one teaspoon per foot of height.

Fertilizer can interfere with the production of blooms in flowering shrubs. Spring-blooming shrubs should be fertilized at a rate of one teaspoon per three feet of height just at the end of their bloom cycle. Use this same rate for summer-blooming shrubs just as they begin to flush new growth early in the spring. Fertilize shrubs with shallower root systems at a rate of one half teaspoon of fertilizer per foot of height.

As with your trees, do not fertilize in the late summer or fall. Fertilizer causes the shrub to push out a flush of tender, new growth, which will be more susceptible to frost damage and die back.

Different shrubs vary in their ability to withstand fertilization; over- fertilizing can result in leaf burn. For specific recommendations, please contact your local county extension agent.

Mulching

Uniformly apply a two- to four-inch layer of mulch, pine straw, or bark to the soil surface. This will aid in moisture retention, weed control, and temperature regulation (keeping the soil cool in summer and insulating the soil in winter). For more detailed information on mulching, click here.

Watering

Improper watering practices are the leading cause of plant loss in the landscape. It’s important to know what each plant needs and the signs that it will give to let you know whether those needs are being met.

Here are some general guidelines for proper watering:

  • Water your trees and shrubs thoroughly after planting.
  • Continue to water plants regularly for the first two years that they are planted. Proper watering is especially crucial during this time as the plants are working to establish themselves in the landscape and to overcome any transplant shock.
  • Deep, less frequent watering is better than frequent, shallow watering. This promotes deep root growth and can reduce water loss by evaporation.
  • Sandy soils drain water much faster than clay soils. In an area with a heavy clay soil, the water percolates slowly into the ground, so water at a slower rate to help reduce run off.
  • Know how much water each plant type needs to thrive.
  • Water the rootball or the area directly below the plant rather than the leaves. The leaves can take in water, but the main uptake of water and nutrients is through the roots.
  • The best time to water is during the morning hours. Afternoon watering tends to increase the chances of water loss through evaporation. Watering at night increases the likelihood of fungal infections.
  • Mulch around your plantings. This helps to reduce evaporation and to suppress weeds.
  • Control your weeds – they will be competing with your plants for the same water.