When and How to Prune Flowering Shrubs

Pruning flowering shrubs is an easy way to encourage beautiful blooms—but you have to know how, when, and what to prune.

Most gardeners agree that spring is a great time to sharpen the gardening shears and get to work. But before you so much as touch a saw, shears, or clippers, you need to understand why, how, and when to prune. You probably think that pruning flowering shrubs is necessary for getting exceptional blooms, but the details are confusing. With many shrubs requiring different types of care, it’s important to know which plants need to be pruned, when, and how.

The following article will help guide you through pruning flowering shrubs so that you can prune with confidence.

Why we Prune

There are only a handful of reasons to prune a shrub, but the overall reason is to improve health and appearance. The specific reasons are as follow:

This exposes more of the plant to light and air and improves the overall appearance. Removing dead wood can be done at any time of year, but is especially effective in early spring when buds begin to leaf out and it is easy to identify dead stems.

Shrubs with obvious signs of disease or infestation by borers or scale insects need to be addressed with a heavy pruning to remove the problem areas. Off-cuts should be burned or disposed of off-site, rather than composting or shredding.

Old wood that is no longer able to flower should be removed to make way for more flowering growth. Flowering plants that have too many budding branches can be pruned back to encourage fewer, larger blooms.

Grafted plants like roses, lilacs, and rhododendrons may have suckers from the rootstock that need to be destroyed. Other shrubs can become unwieldy or develop lopsided shapes if not kept in check with an annual trim.

Pruning should be strategic and purposeful. If none of these reasons are present, then you don’t need to prune.

How to Prune

How we prune is almost as important as why. Following a few very specific guidelines ensures that the plants you prune respond positively and reward you with healthier growth or better flowers.

The first rule of pruning is to use clean, sharp tools. This minimizes the spread of disease between plants and reduces the amount of injury inflicted by dull tools. Bypass secateurs, hand-held pruners with a scissor-action are perfect for cutting stems up to the width of a pencil. For branches up to two inches, a pruning saw will be more effective. For medium-thickness branches to just over an inch thick, loppers will do a tidy job. Between plants, use alcohol or a spray disinfectant to clean the blades and prevent the spread of disease.

If removing an entire branch, cut as close to the parent stem as possible so that you leave little to no stub behind. This will help to prevent disease from entering and spreading to the plant.

If you are trying to achieve a specific shape, cut branches just above buds facing the direction you want the shrub to grow. This will direct growth towards your desired shape.

When to Prune What

Every season brings different pruning duties. Getting it right will determine how your flowering shrubs flourish over the following year. Remember, with the exception of the few shrubs listed for early-spring pruning, most flowers grow on last year’s growth and should not be pruned until after flowering.

The most general rule is to prune spring-flowering shrubs after they have bloomed, and then to remove old stems and branches. The new wood that grows during the year will generate next year’s flowers.

These shrubs flower on last-year’s wood, so the only reason to prune these shrubs is to clean up long, trailing branches and to remove worn-out or dead wood.

Shrubs that need thinning or shaping can be pruned in winter when they are dormant. Late winter is a good time to prune certain shrubs for shaping because it can be easier to see their form before they leaf out.

This is the time to prune the young wood of Peegee hydrangeas and rose-of-Sharon shrubs back to a few buds emerging from the mail stems. Most hydrangeas (except for French hydrangeas) can be cut back almost to the ground. Buddleia can be shaped or cut to the ground to maintain a dense, compact form. Cut all dead and old (older than 2 years) wood from climbing roses, and for hybrid tea roses simply cut back all growth less than the thickness of a pencil as well as dead or weak growth. Abelia, hypericum. summersweet, spirea, and vitex shrubs can be pruned before spring growth begins.

After flowering, cut back beauty-bush, deutzia, forsythia, lilac, and mockorange by pruning old wood from the base.

This is a quiet season for pruning, limited mostly to rambler roses that can be pruned to remove spent blooms and growth that is more than two years old. Summer and fall pruning is generally discouraged because it stimulates growth that will be susceptible to winter injury.

There is never a bad time to cut back dead, diseased, or weak stems and branches from shrubs. Cutting back suckers from rootstock is also allowable year-round.

Overgrown shrubs that have stopped flowering can benefit from rejuvenation pruning. This technique involves cutting all the main stems back to the ground in early spring. While severe enough to delay flowering for a year or so, this ultimately results in a more beautiful, compact flowering shrub. Lilac, forsythia, and spirea respond well to this type of pruning. The bottom line is that pruning properly can help flowering shrubs thrive and produce exceptional floral displays every year.