Pruning: It’s time to prune flowering shrubs

Right now, in the Philadelphia landscape, the spring-flowering shrubs have just about finished blooming. Since cooler days are ahead, pruning your Azalea, Rhododendron, Forsythia, and Lilac bushes is a priority on the gardening to-do list. Based on a close observation of the weather and bloom times observed directly from the Philadelphia garden; if you haven’t already, it’s time to prune the flowering shrubs on your property. These spring-flowering shrubs, as well as most others, should be pruned shortly after blooming but before buds are set in July. Timing is critical in regards to the amount of flowers these shrubs will produce next spring. Cutting back spring-flowering shrubs at the wrong time can stop the plant from flowering for a year or two. For example, on rhododendrons and azaleas, the buds form on the plants during the previous summer or fall. If you prune in the late summer, fall, or winter you may be trimming off your flowers for the following spring.

Pruning is one of the most misunderstood techniques of gardening; it often seems a mystery to new gardeners. The benefits of pruning shrubs are similar to the benefits of getting your hair trimmed. Pruning is the task of snipping, cutting, or pinching away plant parts, and it serves various functions such as part maintenance, part preventive medicine, and part landscaping. It not only improves a plant’s appearance, but it can also correct and repair damage, remove disease, direct growth, increase growth, rejuvenate, control size, improve health, and increase production of flowers and fruit. It may be a big job such as removing a heavy, damaged limb, or it may involve the simple removal of a spent flower. Pruning doesn’t hurt a plant; rather, it enhances the plant’s vigor and beauty. In other words, proper pruning at the proper time is good for your plants.

Trees and shrubs are vulnerable to damaging wounds in their bark and roots caused by both humans and nature. Many times, damage to trees, shrubs, and plants are caused from storms, ice, winter burn to leaves from wind, and even by dogs, cats, or some pesky varmint that runs through your garden or chews on the shrub. Also, as a plant grows, some of the limbs will be shaded out and become weak and eventually die.

Prune old, damaged, diseased and dead wood, as well as wild runners and suckers at the bottom of the shrubs. Prune lanky stems that are out of bounds, and other weak limbs that are on the ground or crossing over each other. This provides better air circulation and does not provide a place for insects and diseases to start. Also be sure to remove dead blooms.

These important basic rules apply to all of the mentioned flowering shrubs:

Never cut more than 1/3 of the plant at one time because too much will stop growth and blooming for next year; unless of course, you need to do radical pruning.
Pruning should be done every 1 -3 years
When pruning, prune to accentuate the natural shape of the plant
Always leave as many leaves as possible for photosynthesis.
Very large plants can be cut back severely to stumps with no leaves; although it could be 1-2 years before the plant begins to fill out with new branches and new foliage; and it could be two or more years before they flower.

Azalea – How to prune Azalea video

Azaleas, and the small leafed rhododendrons, may be pruned anywhere along the stem, because even though you can’t see a lot of them, they have dormant buds all along the stem. Unlike rhododendrons, evergreen azaleas can be sheared each year after flowering to create a dense rounded plant, or they can be sheared for a hedge or border planting. Deciduous azaleas can be cut anywhere on the stem and they will branch from that point, though they should not be sheared as severely as evergreen azaleas.

Rhododendron – How to Prune Rhododendron Video

Many times, the only reason rhododendrons need to be pruned is because they were planted in the wrong place. Most like to grow 12-20 feet tall, so planting to close to the house or other plants is often what makes pruning Rhododendrons necessary. Click here to find out how to find the right Rhody for your space. Light maintenance pruning will not affect flowering for the following year if done now; but cutting back a rhododendron heavily can stop the plant from flowering for a year or two.

Lilac bushes (Syringa vulgaris) - How to Prune Lilac Video

Although lilac bloomed back in late May, you still have time to prune them now without affecting the blooms for next year. Cut off dead blooms and cut every branch ½ back. Be sure to cut back an old lilac tree gradually. Don’t forget the suckers that sprout at the bottom of the lilac bush.

Forsythia – How to Prune Forsythia Video

Forsythia are fast growing shrubs that can grow up to ten feet tall and just as wide. Pruning is critical in order to control growth. If you keep up with the pruning each year, it helps them to not become leggy, but bushier with more abundant blooms for next year; it also helps control their shape and size. Young plants may only need a little pruning here and there; and forsythia that has overgrown may need to be radically pruned to a foot above the ground. Within two years, it will look like a brand new forsythia.

Click here for more on How to Prune Flowering Shrubs

Click here for more on How to Prune Perennials

Here's what perennials are blooming right now in the Philadelphia Garden: Peonies and Iris, Bleeding heart, Blue Salvia (May Night), Clematis, Corydalis, Dianthus, Dicentra, Epimedium, Nepeta, Oriental Iris. Perennial Geraniums, and Peonies.

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