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To optimize the beautiful shape of your lilac bushes, youneed to prune them each year. Pruning is a very important part of growing andcaring for Lilacs. While some varieties only grow 4 to 8 feet, others can reachup to 30 feet tall. Most will grow in excess of 10 feet. Pruning will not onlyhelp with shape and appearance, but also impact plant health and vigor and theprofusion of flowers.
There are right and wrong ways to prune a lilac. There isalso a right and a wrong time. For maximum beauty it is most important to pruneyour bush immediately after they are done blooming during the growing season.Make sure to remove the spent bloom with your clippers. This will keep theplant from growing seeds and encourage creation of next year's buds.
rSeasonal pruning should be done as soon as the flowers have faded.
rCut small suckers and shoots at or near ground level, or where it comes out ofthe main trunk. It is okay to clip off old, dead flowers at the base.
rLeave a few strong and healthy new stalks each year, especially if you areplanning to trim back old wood. (top)
Lilacs should be pruned and maintained each year. The plants should be full looking, yet not overly bushy. If the plant is too bushy, the inner leaves do not get sun and air circulation. A lack of oxygen to the plant is an invitation to plant disease.
Trim larger stems from the center of the bush to increase ventilation. It will also afford more room for newer shoots on the outside of the plant to develop.
Next year's flower bud develops early, even though you maynot see it. Often an inexperienced gardener may trim the tops several inchesback. While the plant might look a lot nicer, they loped off the next year'sflowers with one pass of the hedge trimmer. By the way, avoid using hedgetrimmers. It gives a too trimmed appearance. Lilacs are not hedges.
First of all, maintenance pruninginvolves removing all dead or broken wood, branches that are less than 10” fromthe ground. Also, branches too curved or too close together and any that arerubbing or crossing.
By removing some of the weaker,old and less vigorous branches each year, maintenance pruning is also a way torejuvenate a shrub. Removing branches gradually won’t radically alter theshrub’s appearance and, since it may take the new stems up to five years tobloom, your lilac will continue to flower each year. On grafted plants, it isimportant to keep only those branches growing above the graft union. On others;Suckers that form at the base of the tree every year can be selected to replacethe main branches. Choose a few of the strongest suckers and get rid of the rest.(top)
Trim back any branches that stick out from the main bush, and that are not appealing to you.
Topping your lilac is not encouraged. Generally a flat top is less appealing. A slightly rounded top looks great and helps promote better flowers.
In trimming and pruning your bushes, remember, beauty is the eyes of the beholder. If you like a tall bush let it grow tall. If you prefer a wide bush, encourage shoots that have spread out from the main bush. (top)
If a lilac bush has become overgrown, or is too large ortall for the area you have allotted it, there are a couple of ways to get itback in shape.
The three year plan is very popular. A lilac shoot takesabout three years before it produces a flower. So plan to eliminate 1/3 of theshrub each year, selecting the oldest stalks. Cut them down to just above thelevel of the soil. As you do, allow new shoots to grow to replace the old ones.By the end of three years, the entire shrub will have been replaced, and youwill not go without lilacs for that period of time. Then, continue the cycleeach year. (top)
If life with your overgrown shrub has just become unbearable, remove all old stock and leave just new shoots.
Do this during the winter, when the plant is dormant.
This is pretty drastic. And, you will go a couple of years without lilac flowers.
But Lilacs are hardy. As long as there are a few healthy new shoots, they will grow back.