Lilacs need to be pruned regularly – at least once a year. When you prune your lilacs on a regular basis, it helps the plants to bloom profusely each year and also remain in your desired shape and size. In addition, regular pruning of the plants helps them to remain healthy and bear large bunches of flowers in large numbers. It is essential to prune lilacs grown in public and arboretums, as they need to look their best during the spring. Lilacs grown in home gardens can be pruned annually or less often. However, infrequent pruning of lilacs makes them look unkempt, as they will overgrow soon. This will eventually make your job difficult when you want to prune the plants. In fact, annual pruning of lilacs is necessary for small gardens where the space is very limited. If you don’t prune them every year, they will not only overgrow and overshadow other plants in the garden but will also look unsightly.
Even cutting the flowers of lilacs to bring them indoors for decoration is a form of pruning. However, this is not a very systematic means to prune lilacs, but it is not a bad idea either. In fact, when you remove any part of the shrubs – foliage or flower, they are quick to replace them with new leaves and flower buds to be ready for the show in the following spring. Nevertheless, cutting the flowers is actually a very random process and, hence, cannot be called a dependable means of pruning. Usually, people who want to trim the plants by picking the flowers only cut the blooms that are accessible to them. Moreover, they may also infect the plants if they do not use sterilized knives or handles to snip off the blooms.
Therefore, you will be requiring a pruning saw, if possible a curved one having a strong handle, and secateurs and pruning shears to undertake the task of pruning effectively. In order to cut back branches that are broader than an inch (2.5 cm), you may use pruning shears with long handles, as they will make the task easier. In addition, ensure that the edges of your pruners and saws are always razor sharp. At the same time, sterilize them every time between cuttings with Lysol, by wiping the edges with alcohol or dipping them in a homemade sterilizing solution prepared by using domestic bleach and water in the ratio of 1:10.
You need to follow some guidelines while cutting the lilac branches. For instance, you should only cut them in three places – the place just higher than a bud, a flush either at the ground or with any adjoining branch. You should undertake pruning the lilacs, irrespective of their species or cultivar, immediately after their blooms have withered. This is the time when you can best manage the plant. In fact, most people do not like the appearance of faded lilac blooms and, hence, when you prune the plants at this time, it also helps you to deal with deadheading.
Lilac shrubs and trees develop new leaf as well as flower buds in summer for the ensuing season. Therefore, you should never undertake pruning so late, as it is possible that you will cut some flowers of the next season while pruning the plants during this period. In fact, the majority of the hardy lilac shrubs that bloom in spring usually develop their flowering buds in the previous season. Therefore, it is advisable that you make yourself free for a day for not only pruning your lilacs, but also other plants like honeysuckle, caragana (Caragana spp.), mock orange (Philadelphus), forsythia, white spiraea, double-flowering plum and ninebark (Physocarpus opulifolius). However, you may always cut back diseased, broken, winter-killed or rubbing branches of lilacs any time during the year. In such cases, you should prune the plants up to an appropriate place below the area where the problem lies immediately when you notice the damage or problem.
Never use hedge shears to prune lilac shrubs with a view to making their heads appear rounded. While pruning cedar or yew in such geometric designs may be an effect, it will harm the natural appearance of lilacs. Moreover, it will also do away with the flower buds and promote new branching at the plant’s apex. At the same time, be careful not to cut back all the branches near the base of the plant as well as the branches that arch close to the ground in order to allow the lawn mower to run close to the plant’s base. Removing the low branches will deprive you of the new growth that will provide you with plenty of blooms while cutting the arching branches will damage the shrub’s natural shape. In any case, not much will grow so close to the base of the plant as the area is too shaded. In case you find it necessary to mow below the lilac branches, first raise them. On the other hand, you may remove the sod and place enough mulch or grow a low growing plant that can tolerate shade below your lilacs.
Do away with the new roots (suckers) of your lilacs that emerge from below the joint where the plant has been grafted. Usually, the foliage of the lilac will appear somewhat different and possibly much smaller compared to the variety you prefer. In case you allow the suckers to grow till the plant comes into bloom your lilac will bear various types of blooms. In addition, the graft shoots that are below are allowed to grow, sooner or later they may take over the shrub itself.
If you are growing lilacs for their flowers – generally that is the reason why most people grow lilacs, it is very important to bear in mind that these plants actually flower on the growth of their previous season. Therefore, if you prune the plants late in autumn or sometime during the beginning of the spring with a view to making your garden tidy, it is possible that you may also remove all the flower buds from the previous season. Hence, it is advisable that you should allow the plants to bloom in their full glory and take delight in their wonderful aroma. Prune the plants immediately after the plants have finished blooming for the season.
When the flowering season of the lilacs is over and it is time for you to prune them safely, the first thing that you need to do is to remove the faded blooms, just as you deadhead all other annual and perennial plants. In other words, what you need to do is to cut the spent flowers. If you allow the spent flowers to remain on the plants, the lilac is likely to spend most of its energy in producing seeds, rather than engaging more vigorously in developing the flower buds for the subsequent season. Although seeding is the end result of flowering, you always do not require the seeds. So why should you allow the plants to waste their energy on seed production at the cost of the blooms for the next season? Therefore, the simplest thing to do is just cut the flowers after they are spent. Even doing such a simple thing to your lilacs, they will flower profusely year after year for you to take delight in their beauty and fragrance.
Many of us often see lilacs in miserable conditions. These plants just appear as a bunch of stick with some blooms appearing at their top. In such cases, you can hardly see the blooms, forget about enjoying them. Often this is inevitable, mainly because of the species’ pattern of producing flowers on the growth of the previous season. When the appearance of lilacs becomes gangling or they overgrow, you should know that the time has come to revitalize the plants. Generally, it takes a period of about three years to rejuvenate a lilac properly.
In the first year, after the flowering season of the lilac, you need to cut the oldest and thickest branches, thereby removing about a third of the plant’s entire branches. Cut the branches as far as possible close to the ground. In the second year of revitalization, again cut one-third of the branches of the plant after the flowering season. In the third or final year, you only need to cut the remaining older branches, which you might have missed severing in the first two years. This method of revitalizing the plants by cutting away most of the branches of the lilac shrub or tree may seem to be a drastic one. However, it will promote new branch growth and these branches will produce more blooms compared to the older ones. Moreover, as the blooms will appear on branches close to you, you will be able to enjoy them better.
Rejuvenating lilacs in this manner is known as basic pruning that can be undertaken at any time of the year, especially after the flowering season is over. Most people usually undertake this during the spring, because this is the time when you can easily identify the branches that have not been able to thrive the winter. In case the entire branch is not dead, just cut off the dead portion a little higher than a live node. On the other hand, if the entire branch is lifeless, just cut it down completely and dispose of the dead wood.
It is important to note that your lilacs will grow best when they are left on their own. So if you try to prune these plants to give them a cubical or oval shape, it will not only increase your workload but may also lead to fewer blooms. Usually, lilacs bloom prolifically, but pruning the plants to give them different shapes will result in cutting of their branches that may possibly produce a large number of flowers in the ensuing season.
However, there is no doubt that the lilacs require regular pruning as well as shaping with a view to make them look attractive and also to prevent their overgrowth. You should definitely prune the branches that cross or rub against other branches. In addition, occasionally you will find one or two branches of your lilac growing larger than other or grow in odd angles making the shrub look awkward. It is essential to cut back such branches and you need to do all things possible to sustain the attractiveness of the shrubs.
Before we conclude, it is worth mentioning that you may also have to deal with some other problems, such as the runners produced by lilacs. As you will want to contain these runners, you will have to trim them from time to time – possibly a couple of times every season. Never allow the runners to grow very large or become unmanageable.