05/29/2015

It is Time to Prune Lilac, Forsythia and Other Early Spring Flowering Shrubs

Ever wonder why your Lilacs or Forsythia don’t bloom like your neighbor’s? It could be that they don’t get as much sun, or maybe you’re not feeding your plants as well as your neighbor is, but it’s more likely that you are not pruning your plants properly.

First, timing is important, especially when pruning early spring blooming shrubs. Early blooming shrubs develop their flower buds during the summer and fall of the previous year. This is often called “blooming on old wood.” Therefore, as a general rule, shrubs that begin flowering before June 15 should be pruned soon after flowering. Pruning these shrubs in late summer, fall or early spring will remove the flower buds and therefore the flowers.

Second, pruning annually is also important for these types of shrubs. If you don’t spend a little time each year pruning these shrubs, your Forsythia can turn into an overgrown tangle and your Lilac will develop stems the size of small tree trunks. Shrubs bloom best on younger branches that are more actively growing. If you allow your shrub to become old, woody and overgrown, it will soon not have much flower power.

Now is the time to get started. If your bush is not terribly overgrown, it probably just needs a little TLC. Ideally, once you have a mature shrub, you should be removing about 1/3 to 1/4 of the oldest, heaviest canes each year to thin the plant. Doing a little pruning each year will make your job easier, and it will provide branches of various ages, which will provide a more prolific bloom display. To thin the plant annually, cut the oldest branches off as close to the ground as you can. Also, cut out any broken or damaged branches, as well as any that cross and rub each other.

If your shrub is providing little-to-no bloom, and is an overgrown tangled mess, you may want to consider taking more aggressive action to rejuvenate it. For Forsythia, you can cut the entire bush nearly to the ground. Roughly four inches is a good amount to leave behind; it will grow new flexible branches during the summer and fall, and by the next year, it will be looking good again.

Lilacs can be treated in a similar way by cutting all of the older stems bigger than your index finger to the ground. This will promote growth of the younger stems and in a year or two it will be back to blooming beautifully.

Here are a few tips to keep in mind:

• Prune out one-third of the older stems each year soon after flowering has stopped using a good set of pruning shears or loppers. Cut the individual stems back to the base of the plant.
• After you remove the older stems, you can cut back the stems that are taller than the rest of the shrub or that stick out to give it a more uniform look. Make the cuts just above a bud, leaf node or lateral branch at the desired height on the stem.
• Remove dead, damaged or diseased limbs at any time throughout the year. Cut dead stems back to the base of the plant. Cut damaged or diseased stems back several inches into healthy wood, making the cut just outside of a bud.

With these few easy tips in mind, you can keep your shrubs blooming beautifully for years to come with minimal work each year.