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  • Writer's pictureKassi K.

Pruning Lilac Bushes: How and When to Prune Lilac Bushes

Lilac bushes are a favorite among many. Their fragrant and beautiful clusters of lavender-purple blooms emerge in the spring and decorate any landscaping, attract pollinators of all kinds, make for an excellent cut bouquet, are easy to care for, and so much more. While lilacs are not a complicated flowering shrub, they do have some specific care and maintenance requirements especially when it comes to pruning lilac bushes that are important to know about if you want to enjoy their blooms year after year.

pruning lilac bush

Why Prune Lilac Bushes?

Regular pruning is an important aspect of maintaining all trees and shrubs, not just your lilac bushes. Several reasons for the importance of pruning trees and shrubs are that it helps to encourage new growth, can eliminate safety risks, can help avoid pests and disease, and helps to create an aesthetically pleasing shape. For lilac bushes specifically, the primary purpose of pruning is to maintain shape and to encourage vigorous blooming. It is important with lilac bushes to maintain a balance of mature stems to provide structure and new shoots that will produce flowers. Lilac bushes that are very old or that have not been maintained every year can lose their vigor. Such bushes usually have very thick stems and minimal flowering and can benefit from heavier pruning that will help to rejuvenate the shrub over a period of a couple of years. To keep your lilac bush in good health and blooming profusely, pruning is necessary!

When To Prune Lilac Bushes?

It is very important to know when to prune lilac bushes, as timing is everything with these flowering shrubs. Lilac bushes bloom in the spring and quickly set their flower buds for the following year after their blooms fade for the season. For this reason, it is very important to prune your lilac bush almost immediately after its current blooms have faded. If you wait too long, you can very easily prune off all the flower buds for the next season, meaning your lilac bush will not bloom the following spring. The same goes for any late season pruning. If it is necessary or you can't resist the temptation to prune your lilac bush, just know that you are sacrificing next year's blooms and will have to wait another full season to get to experience this flowering shrubs' blooms.

Faded lilac flowers. When to prune lilac bushes

How To Prune Lilac Bushes

Pruning lilac bushes is not a hard task, but there are several steps to take and important things to keep in mind when going about your pruning endeavors. One important thing to remember when pruning any trees or shrubs is that you should never remove more than 1/3 of the living tissue of the plant at one time. The end goal with lilac bushes is to have 10-12 main stems all between 1 and 2 inches in diameter. Maintaining this throughout the life of the shrub will help encourage it to bloom the most and will keep your plant a manageable size. Here are the general steps you should follow for how to prune lilac bushes.

1. First Prune Dead or Diseased Parts of the Plant

The first thing to look for when pruning any trees or shrubs is dead, damaged, or diseased portions of the plant. It is important to remove these portions of the plant as new growth cannot come from tissue in this state. Removing any portions that may be in this state also helps to stop the spread of disease and prevents further damage from happening.

2. Remove Large or Old Parts of the Plant

When looking for living tissue to begin pruning back, start with the oldest parts of the plant. Any branches or stems that are thicker than 2 inches in diameter should be cut back to the base of the plant. These older stems are less likely to produce an abundance of flowers, so pruning them back will encourage the growth of new, more vigorous stems. Cutting back these larger stems will also help keep your shrub a more manageable size. Avoid cutting off just the tops of these stems, as this can result in an odd and unnatural shape.

3. Trim Back Remaining New Growth

Now is the time when you can trim back some of the new growth of the plant. This is not necessary, so if you are close to having removed 1/3 of the plant already, consider skipping this step. If you are aiming for a shorter and more bushy plant, trim the remaining new growth back to an outward-facing bud. In other words, trim about an inch above any buds that face away from the center of the plant. This will encourage outward growth and more branching, resulting in a denser, more bushy lilac.

Purple lilac flowers blooming

Tips For Pruning Lilac Bushes

If you are looking for more information on lilac bushes, how to prune lilac bushes, or when to prune lilac bushes, we are here to help! You can research different varieties of lilac bushes with our Plant Finder or you can come into the Garden Center to shop available plants and talk with the pros about care and maintenance requirements for hundreds of different plants that are suited to our environment here in Colorado. If you are interested in our landscape design and installation services, learn more on our services page and fill out a contact form today!


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