Anchorage Daily News

Q. There have been so many beautiful lilacs blooming in Anchorage. Why won't mine flower?

A. The key to this puzzle likely lies with the flower buds. In most species, the buds that produce flowers formed last year. The exception is late lilac, which flowers on the current season's growth. Flower buds are produced soon after the plants stop flowering. This means there's a narrow window of time when plants can be pruned without affecting next season's blooms.

One of the most commonly planted lilacs in Southcentral Alaska is the Canadian lilac. These lilacs can grow two stories tall. An older plant can be pruned to look like a small tree, but you can't make a tall lilac short by cutting off the top of its branches. If you want a hedge, plant cotoneaster. If you must shape your lilac, do it right after the plant has finished blooming.

In addition to poor pruning, moose could be the reason your lilac isn't blooming. If moose browse plants in late summer or winter, there will be no buds to produce flowers next June and July.

Your lilac could also be too young to bloom. It often takes nine years for the old-fashioned common lilac to blossom. People plant them because they're exquisitely fragrant. Early lilac and Canadian lilac begin flowering at an age younger than many other types of lilacs.

If your lilac was in bloom when you purchased it, be patient. It's not uncommon for a plant to remain flowerless for the first few years after transplanting. Water thoroughly, but don't keep the soil soggy. Lilacs don't like wet feet. Fertilize, but only once a year. Too much nitrogen leads to excessive leafy growth and no flowers. And don't keep fiddling with lime. It's true lilacs like alkaline soil, but they also grow well in slightly acidic soil. Their optimum pH range is 6.0 to 7.5.

The only other reason your lilac won't bloom could have to do with shade. Lilacs need at least six hours of direct sunlight daily to produce flowers. If you think it's too shady, move the plant now. Don't wait for it to get larger.

Once your plant begins flowering, encourage a good crop of blossoms annually by cutting off the seed capsules. Remember to do this soon after they're formed. Fortunately, not all lilac species produce a lot of seeds. Low-maintenance lilacs include dwarf Korean lilac, Manchurian lilac and lilacs in the new "Fairy Tale" series. It's difficult to determine exactly which lilac you're growing if you've lost its label. Mia Peterburs, an intern at UAF Cooperative Extension Service in Anchorage, has put together a chart of characteristics that might help you sort out the possibilities. Contact the CES office at 786-6300 to receive this information.

Julie Riley is horticulture agent for UAF Cooperative Extension Service in Anchorage.

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