Thursday, May 27, 2010

Lilacs in the (Nova Scotian) Dooryard

The topsy turvy weather here in Nova Scotia has accelerated the bloom period for many plants this spring, and for a lot of us, lilacs are approaching peak bloom several weeks ahead of schedule. Late spring always brings a heady fragrance to the air as the lilacs open their blossoms to the great delight of hummingbirds, butterflies, bees, and even human beings.

Did you know that Canada holds bragging rights regarding lilacs? The Royal Botanical Gardens in Hamilton, Ontario, grows a remarkable collection of lilac species and varieties, and is also the international registrar for new lilac cultivars.

Not only do we Canadians hold bragging rights about lilac registration, one of the best hardy lilac hybrids, the Preston lilac, (Syringa x prestoniae) was developed in 1920 at the Central Experimental Farm in Ottawa by Isabella Preston (1881-1965). Miss Preston is worthy of bragging up too, as she was the first woman to work as a plant hybridizer in Canada. Preston lilacs are extremely winter hardy and bloom later than other species, with drooping clusters of very fragrant blossoms. They tend to grow to a substantial sized shrub (10-12 feet high and wide) but seldom produce suckers. We carry 'Miss Canada' and 'James McFarland' at Baldwin Nurseries.

Lilacs require at least 6 hours of sun daily, and grow best in well drained soil that is not overly rich in nitrogen. The shrubs bloom on old wood, so resist the urge to prune them in spring if you want flowers. After blooms are spent you can trim back the plants, removing weak wood and most of the suckers that form at the shrub’s base. Some people dig up their suckers and shade them with others, always a nice way to add to a friendship garden.

One of the most common questions asked by gardeners is “why won’t my lilac bloom?” There are a number of possible reasons and solutions for non-blooming plants:

1. Flower buds have been pruned off. Don't prune it at all, at least until you do get flowers; then you can prune after bloom, but don't wait too long as lilacs form next year's flower buds not long after they flower.
2. Wrong sort of fertilizer. A fertilizer high in nitrogen will produce good growth but no flowers. Look for a fertilizer with a higher phosphorous number (middle number in formulation eg 5-10-10) They don't need a lot of fertilizer--in fact many gardeners never fertilize their lilacs at all, and so often we see old varieties growing around abandoned homesteads, where they have had no care for years!
3. Shrub needs more light. You can calculate the number of hours in full sun your plant is getting. Less than six hours and you’ll see few or no flowers.
4.Immature shrub. While they often flower in containers where they're under stress, lilacs need a few years to mature and bloom once they've been transplanted. Just be patient.
5. Not enough water. Though that's hardly been a problem the past several summers, it can be a problem.
6. Soil acidity. Most soil in NS is acidic, and lilacs like it neutral to slightly alkaline. You can get a pH kit to test this. Is your lilac near acid loving plants like rhododendrons, azaleas, etc? If they're doing well and it's not, that could be your problem—soil that is too acidic.

What you choose for species and hybrids depends on your garden size and your preference in colour and flower form. Lilacs come in a host of shades from white and cream to pink, mauve, various shades of purple, and even one bicolour! If you have a small garden, don’t worry: there are compact varieties, including the extremely fragrant cultivar 'Miss Kim', which only gets a few feet tall.