Pruning brings out best in lilacs

In a few short weeks, Inland Northwest gardens will be filled with the fragrance of lilacs.

All across the region, even the plants left to fend for themselves on empty lots and abandoned farms will be covered with flowers in a dozen shades of purple, white and even yellow.

Spokane truly will be the Lilac City.

Lilacs are an easy plant. They transplant easily, can survive the toughest winter and are fairly drought tolerant.

In our climate that makes them a fairly perfect plant.

But what happens when they grow into lanky monsters or just become untidy? That’s when it’s time for a pruning to get them back to a more manageable size and shape.

Pruning lilacs is a matter of timing. For most common ones, the best time is in the spring right after they finish blooming says Geri Odell, a well-known lilac collector and a leader in the Spokane Lilac Society.

“That’s when they form buds for next year,” she says. Lilacs bloom on old wood, which means the flower buds are on wood that grew last summer and wintered over.

In other words, if you pruned your plant when it was dormant this winter, you cut off all of this year’s blooms.

Here’s how to prune correctly: Within two weeks of the flowers fading this spring, nip off the spent blooms to just above the two new buds that should be popping out below the fading flower. Each of these two new buds will produce a set of flowers next year.

Regular trimming like this will help keep your plant from growing out of bounds and turning into a monster-size plant with few blooms.

If lack of pruning has turned your plant or hedge into a lanky row of green stalks, then a full renovation is in order. This process will take three years.

First year: After the plant has bloomed, remove most of the small twiggy stems at the base of the plant, close to the ground. Dig or pull out any suckers that have sprouted outside the main part of the plant if you can.

Examine the remaining thick stems and choose a third of the oldest and cut them to the ground.

Second year: Remove the second third of the old stems and continue to get rid of the twigs at ground level.

Third year: Get rid of the last third of the old stems.

Using this system, you will continue to get blooms on the remaining stems while new ones will grow in. Because you cut the old ones completely to the ground, in three years you have a brand new plant.

Does all this seem too complicated and like too much work? Then skip it, says Odell.

“It isn’t absolutely mandatory to prune them; its aesthetics,” she said. Lilacs will always set buds somewhere on the plant. Just look at all the old plants blooming on abandoned lots around the city.