Pruning Tips: How to Prune a Shrub
Before pruning, it is important to understand the habit and shape of the plant that you plan to prune. As a general rule, all shoots grow outward from the tip. Every time tips are removed, it stimulates the plant to grow out lower buds. Buds can be found at the nodes and upon pruning, buds can be expected to sprout from nodes. Each node can produce up to three buds. A node is the thing that connects the leaves to the branches.
Shrubs are known to adapt three kinds of growth habits – mounding habits, cane habits, and tree-like habits. Shrubs with mounding habits include evergreen, azalea, and spirea. Mounding shrubs commonly have soft stems and leaves. The stems are also bendable.
Some cane habit shrubs are forsythia and nandina. This type of shrub grows upward through several branches coming from the base. It is very similar to bamboo. Bamboo however is classified as grass.
Tree-like shrubs on the other hand are like trees. They have woody and evenly divided branches. These include witch hazel and rhododendron.
Types of Pruning Cuts
Basically, there are two kinds of pruning cuts — heading cuts and thinning cuts. Heading cuts urge buds to sprout on nodes nearest to the wound. The direction of the remaining bud at the top will dictate the direction of the new bud or buds. Doing selective head cuts will help keep the plant’s natural form. Indiscriminate heading cuts however are ill-advised as this will most likely result in quick regrowth from the lower buds which will make the shrub look unkempt. Non-selective cutting is only reasonable when cutting in a hedge or topiary.
Thinning cuts, on the other hand, are done to remove braches from where they sprout. This is mainly used in easing shrub density without encouraging regrowth. This should also be done in moderation.
Pruning cuts should be done at a proper angle. Pruning a quarter of an inch above the bud is the correct way for heading cuts. The cut should be sloping down in a direction away from the bud. The tip of the cut should not be lower than the bud as pruning lower than the bud may cause the bud to wither. For thinning cuts, the proper way is to cut directly parallel to the above parent or side branches.
Experts say not to coat pruning cuts with paint or wound dressing as these will not avert decay and encourage wound closure on the shrub.
Deciduous shrubs need regular maintenance pruning to remain healthy and leveled with its surroundings. Normally, maintenance pruning should be done at the moment of planting, or following the rejuvenation of older shrubs
Gardeners should regularly and properly cut off dead or broken branches – more importantly for diseased branches. When doing this, one should prune at the healthy part at a good distance below the dead or diseased area. Disinfect your pruning shear after every cut to prevent the spread of plant disease. You can use Lysol, Listerine or rubbing alcohol as disinfectant as Pine-Sol and bleach is not good for your pruning shears.
Maintenance pruning on cane habit shrubs can be difficult if you do not know where to cut. To decrease height, start by cutting the tallest stems at the center up to ground level. You then proceed by thinning out the remaining stems that are crowding the center. Additionally, also cut those that go in unwanted directions.
To decrease the height of mounding types, cut only the branches that extend the most. The cut should be made up to the inside of the shrub mass so it will become invisible. This will help reduce size of mounding shrub by 30 percent and will in no way affect the shrub’s shape.
Tree-like habit shrubs are perhaps the most difficult to maintain. You start off by removing any branches that rub against each other. After that, make some more cuts to open the center of the shrub. It is important to keep the crown open and make sure that light is able to penetrate by use of thinning cuts. Also, prune branches that extend to the ground as well as suckers coming from the roots. Do all of these before making heading cuts. Most tree-like shrubs can tolerate losing up to a quarter of their branches so do not hesitate to make the necessary cuts.
Old shrubs usually grow disproportionate to their environment and may contain great amount of useless wood. There are mainly two techniques being used to rejuvenate old shrubs given that they can still survive and are situated in a good location. When pruning with the goal of rejuvenation, bear in mind that not all plants react well to drastic pruning. A few shrubs that can tolerate extreme rejuvenation include abelia, dogwood, honeysuckle, hydrangea, lilac, mallow, rose of Sharon, spirea and St. John’s wort. Also, the ideal time for such pruning is during early spring when the buds have just sprouted. Additionally, these plants will become quite sensitive and can wither. As such, they should be given special care. Make sure that the plant gets enough fertilizer, water and pest control. As a gardener, one should also consider the effects that the rejuvenation will bring to the landscape. Will the landscape still remain attractive?
The first method used in rejuvenation starts with removing the entire plant 6-10 inches above ground. This will require the use of heavy lopping shears and a pruning saw. By mid-summer, start cutting off half of the new canes and head several of the remaining canes. Keep in mind to prune to buds that point outside so that density can easily be controlled.
The second method used in rejuvenation is a more gradual method. Initially, remove one-third of the oldest and unproductive branches. By the next year, proceed to cut half of the old stems. After another year, prune the remaining old branches. If all is well, the old wood would easily be replaced by fresh stems. While this process takes a large amount of time, it will not ruin the landscape.
When to Prune
Different plants react to pruning in different seasons. However, generally, the best time to prune is by the end of winter up until early spring, just before the buds start to appear. However, for flowering shrubs that bloom in spring, it is best to move the pruning until after the flowers have bloomed to still be able to maximize the floral display.
Pruning in the summer is likely to limit the increase in suckers and foliage. If the shrub is set to bloom on summer, it is best to do the pruning early during spring season or immediately after the flowers have bloomed in summer.
Pruning late in summer or during early fall results in strong regrowth rate which can sometimes lead to cold damage during winter. Whenever such damage has been observed, prune immediately.