What to Prune in What Season: Flowering Trees and Shrubs

What to prune and when to prune are the two top questions that I get asked as a Master Gardener. Pruning, I tell people, is not only paramount to how your plants, shrubs and trees look but also vital to their health. Pruning is a necessary task that you must undertake if you wish to have a thriving and attractive landscape.

While pruning is essential for most plants, there is some flexibility when it comes to degree and frequency. Some plants require a lot more maintenance than others, and for folks not looking to spend a whole lot of time on upkeep, these are always best.

Pruning any plant is a way to shape it and to remove dead, diseased or damaged parts. Dead stems attract insects which encourage disease. Crossed branches and up-shoots from trunks or side branches also hinder sunlight and oxygen from getting to the plant.

The first step to understanding how to care for the vegetation in your landscape is to understand just how your plants grows, when they bloom and when they are dormant. Pruning at the wrong time can spell disaster for new growth and even sabotage a plant’s overall health.

Follow these easy pruning tips for best results when pruning flowering trees and shrubs, hedges and foliage shrubs.

Spring Flowering Trees and Shrubs

Trees and shrubs that bloom early in the spring season such as lilac, rhododendron, magnolia, mock orange and forsythia, all bear flowers on wood formed the previous year. The absolute best time to prune these plants is immediately after they finish flowering in late spring. Pruning them later in the season or in the winter will seriously hamper their spring blooming power. To keep your spring bloomers be as healthy as possible, remove 1/4 to 1/2 of the oldest shoots all the way to the ground - this will allow younger stems to thrive.

Summer Blooming Trees and Shrubs

Plants such as butterfly bush, potentilla and crape myrtle bloom in the summer and should be pruned while dormant during the winter season or in very early spring before the new growth starts. To control size you can even cut bushes down to the ground in late winter. For tall bushes and trees, use a pole pruner that has a rotating head.

Special Pruning Projects

You'll find that some plants don’t fit entirely within the spring or summer blooming categories. For these, you'll need to know exactly when and how to prune to keep them looking their best.

Hydrangeas: Most common hydrangeas such as pink, blue, or white mopheads, lacecaps and oakleaf varieties bloom on old wood. These bushes are best pruned before midsummer. Pruning them in winter or early spring will remove buds. Reblooming varieties, such as those in the Endless Summer Series or Let’s Dance Series, bloom on new growth, in addition to old wood. This makes pruning timing less critical. If you cut some flower buds by trimming old wood the plant will still bloom on new wood. PeeGee and Limelight varieties flower on new wood and can be pruned any time apart from just before they bloom.

Foliage Shrubs: Bushes such as barberry and burning bush are valued for their attractive foliage and can be pruned any time apart from late fall. As soon as you prune bushes such as these, new growth begins to form. If you don't give the bush enough time before the cold weather arrives, the growth won't harden. Major pruning is best reserved for when the plant is dormant in winter.

Roses: Many people never get a change to enjoy the beauty of roses in their landscape because they fear they are high maintenance. If you know how to best prune roses, they can be your best friend, bringing brilliant color and elegance to any corner of your yard.

• Modern ever blooming roses, such as hybrid teas, grandifloras, miniatures and floribundas flower on new wood. To keep these roses looking their best prune up to one half of the plant’s height and thin out the canes in early spring. Be sure to remove all small and weak canes and leave about 3 to 5 healthy canes that are evenly spaced around the plant. Leave 3 to 5 outward-facing buds as well.
• Modern shrub roses repeat flowering and bear their bloom on mature stems that are not old and woody. You have to be very careful not to over prune these roses, as it will result in decreased flower production. It is best to wait a few years before pruning and allow a natural shape to appear. Prune modern shrub roses by removing one-third of the oldest canes and identify one-third of the youngest canes - remove all others.
• Old garden roses can be pruned in the same way as modern shrub roses with some important considerations per class. Alba, Centifolia, Damasks, Gallica and Mosses all produce flowers on old wood and pruning should happen only after blooming. At this time only prune as much as needed to maintain the plant. You may find that these roses don’t need a whole lot of pruning, apart from thinning and removing old wood.
• Ramblers and climbers usually need a few seasons before they need to be pruned. When you do prune just remove winter-damaged wood. Ramblers can be pruned right after flowering in early summer and climbers are best pruned in early spring. Reduce side shots to 3 to 6 inches, as this will encourage flower production.

Hedges: If you have a manicured hedge on your property, such as privet or boxwood, and wish to maintain a solid living fence, new growth should be pruned as soon as it starts to show. It is important to keep the top part of the shrub a bit narrower than the bottom part so that these branches do not shade the lower ones. Trim the hedge as needed throughout the growing season and stop trimming about six weeks before your first expected frost date for your region. If you want your shrubs to form a privacy fence, allow the them to grow tall and wide enough to provide screening. This way, you can avoid unnecessary pruning and allow the shrub’s natural shape to prevail.

Always be sure to use sharp and clean pruning tools and use caution when standing on a ladder or pruning large limbs. If you are unsure about whether or not an older tree or bush needs to be pruned, or are wanting to do a major pruning job, it is best to consult a landscape professional for advice.

Looking for more pruning tips? Check out "Hands on With Doityourself.com: Pruning."