Frost Nipped White Lilacs in the Bud

It's official. There will be no white lilac blooms in joene's garden this spring. I waited and watched and hoped for the best, but it's clear now that the March weather nipped my white lilacs in the bud. This is my first weather-related gardening casualty for 2012.

You remember March. Early month record warmth caused unusually early leaf-break. Then late month frosts and hard freezes stopped by for a few nights. Apparently my white lilacs just weren't up to the cold. The uppermost leaves are browned and curled while lower leaves are completely normal.

Seasoned gardeners know there can be many reasons for lack of lilac bloom.

• Young or transplanted lilacs may take six or seven years to produce flowers. My white lilacs are not young; they've bloomed consistently for more than a decade.
• Poor pruning will prevent blooms. I prune lilacs as they should be pruned, immediately after they cease blooming. I cut all spent flowers off at the same time so the shrubs put energy into setting new flower buds for the following spring. I've been following this procedure, with much success, for decades.
• Over fertilizing with nitrogen will encourage leaf, rather than flower, growth. I only fertilize with compost and worm castings, and infrequently at that. There was no fertilization around the lilacs in the past year
• Insect- or disease-stressed shrubs may not bloom. My shrubs have no known disease or insect stress.

The late March freeze is the only cause I can think of for the lack of bloom in these two white lilacs.

I feared this freeze might kill the white lilac buds so I covered the larger of the two shrubs with a sheet - it's the one I see most often from the house. But this was a gardening oops, it did nothing but turn the uppermost leaves – those in contact with the sheet - brown. The next morning the shrub left uncovered looked better than the covered one. Not being one to let a good comparison go to waste, I figured I would watch for any bloom differences between the two shrubs.

But the blooms never materialized on either shrub. Both show similar freeze damage though the one I covered has more brown-tipped leaves.

Yet … my purple lilacs are blooming as they have for years. They will be fully open within the next few days.

So why didn't frost thwart the purple lilacs? I cannot say for sure, but my years of gardening experience leads me to think the difference is due to breeding. The purple lilac (Syringa vulgaris) is the plain old common lilac so prevalent in the northeast. The purple lilac pictured above came from divisions of a shrub at my previous home, and that common lilac was decades old.

My white lilac (unfortunately, I misplaced the plant tag and cannot recall the exact cultivar) was bred to remain more compact than the, usually taller, common white lilacs. Often, cultivars are not as tolerant of harsh conditions as the original species. In other words, breeding for smaller size somehow bred out some hardiness.

In 2011, lilacs in my south-central Connecticut gardens bloomed in mid-May. This year purple lilacs will be in full bloom within the next few days, about 3 weeks earlier than last year.

Any plant aficionados out there have any other ideas that might have led to the lack of white lilac blooms? Any other Connecticut or Northeastern gardener making similar observations?

Read more on lilacs for Connecticut gardens from UConn Plant Database.

Garden thoughtfully, and read more Connecticut gardening tidbits at http://www.joenesgarden.com/, where this post originally appeared.