Tips for Growing Lilacs

Lilacs are among the most cherished of garden heirlooms. Their light sweet aroma is a true scent of spring. Lilacs will survive for decades without any attention at all, but they can be magnificent with some proper culture. Lilacs prefer an alkaline soil and since our soil in the Northwest tends to be acidic, it’s a good idea to add a cup of lime around the root zone of each Lilac plant in spring or fall. Wood ashes can be used as a substitute.

An established plant does not necessarily need supplemental feeding, but you can use a fertilizer in which the phosphorous is high (middle number on a fertilizer label, i.e. 10-60-10) to help bloom production. It’s also beneficial to apply a mulch layer of compost.

Should a lilac need pruning to shape, do it just after the flowering period (usually in June). They set up next year’s flowers immediately after blooming, so never do any pruning on a Lilac after July 4^th – you will be cutting off next year’s blossoms. It’s best to cut off spent flowers, even in the plant doesn’t need pruning.

The one disease problem that plagues Lilacs in the Northwest is Pseudomonas syringae or Lilac Blight. Symptoms are blackened leaf edges, flowers and stems.  Prune out affected areas and clean pruning shears with a 70% alcohol solution between cuts. Use a copper based fungicide spray (Microcop by Lilly Miller).  Spray plant two or three times, ten days apart.  Using a fungicide spray is also a good preventative measure in early spring, just as the plant is leafing out. In the fall, clean up fallen leaves from the infected Lilacs to stop over wintering of the blight. Planting your Lilac where it will receive good air circulation also helps.

If you have a Lilac that fails to bloom, it may be due to:
1. Not enough sunshine (they need at least five hours)
2. Improper pruning (only safe time to cut on a Lilac is right after the bloom season)
3. Starvation – the bush may be growing in soil that is practically exhausted of nutrients
4. Plant was originally a “sucker” or “volunteer” from another plant – great way to share plants with friends, but sometimes they are non-bloomers. Plants from Cedar Creek Farm are all started as propagation cuttings

To prolong cut Lilac flowers for bouquets, use a hammer to crush the ends of the stems so they can drink in more water. Keep bouquets out of direct sun and change the water daily.

There is an amazing variety in Lilac color, habit, bloom size and flowering time. There are about 20 species and hundreds of hybrids to choose from. By having different types, you can extend the bloom time in your garden. Prized for their heady fragrance, heart shaped leaves and delicate blossoms, lilacs have captivated gardeners for centuries. As one Lilac lover wrote, “The sniff of their perfume in the garden is the very heart and soul of memory”.