© Janet Davis
What gives lilacs their unique appeal?
Lilacs are springtime favorites and their appeal, of course, lies in the
old-fashioned beauty of those dense flower panicles in shades 
from pure white through lavender, rich purple, mauve, blue and
magenta. There’s even a yellow. That, and their unmistakable perfume which,
carried aloft on a light spring breeze, has long inspired lovers and poets and
recalls for many of us nostalgic memories of childhood gardens.
Several years ago, I asked Charles Holetich, then lilac specialist for the world-renowned lilac collection at the Royal Botanical Gardens (RBG) in Burlington, Ontario, for some hints on caring for these lovely spring shrubs.
JD: What’s the best location for lilacs?
CH: Lilacs prefer open, sunny locations and neutral soil, though they will grow in slightly alkaline or slightly acid conditions and are found in both.
JD: What about drainage?
CH: They dislike wet feet, so if planted in clay-type soil which has a tendency to retain moisture, you should make a hill about 2 feet high and 8-10 feet wide, so excess moisture seeps away.
JD: If it’s located in full sun, does a lilac shrub need to be fertilized?
CH: If it has too much foliage and not enough bloom, that means it’s high in nitrogen. In order to induce flower buds, you should feed it with a high phosphate (middle number) fertilizer like 4-12-8 or 5-45-15. This should be done immediately after flowering because next year’s buds are being formed in June, July and August.
JD: What about all those
seedheads? Must they be removed and how can you reach the top ones
on a big shrub?
CH: When summer has adequate rainfall,
then it doesn’t matter because there’s sufficient energy to bring enough
nutrients from the soil to satisfy the formation of both seedheads and
flowering buds. But in drought summers,
you should remove seedheads and water deeply, about 5-6 inches once a
month.
JD: Pruning confuses a lot of lilac owners too.
CH: I think the ideal for a multi-stemmed lilac is to have 9-15 stems of different thickness positioned so they don’t rub each other. Once this is achieved, then every two years or so, you should remove one or two of the oldest stems at ground level, keeping up to 3 new shoots. Then the next year, you can decide which of the three is the best to keep and remove the others.
JD: How
tall should a lilac be kept pruned?
CH: I’m a strong believer that a lilac should be deliberately kept pruned at between 6-9 feet.
Favorite Lilacs
Many botanical gardens and lilac suppliers publish lists of their top lilacs. Here are 20 lilacs culled from the websites of the Chicago Botanic Garden, Boston’s Arnold Arboretum and well-known lilac supplier Select Plus International:
Common Lilac (Syringa vulgaris) and Hyacinthiflora (Syringa x hyacinthiflora) cultivars:
· Agincourt Beauty – single-flowered, large-florets, violet-purple
· Avalanche – single-flowered, white, very floriferous
· Charles Joly – double-flowered, very fragrant, magenta
· Excel – early-flowering, single, very fragrant, lilac
· Katherine Havemeyer – double-flowered, very fragrant, pink
· Krasavitsa Moskvy* – double-flowered, white (*This one regularly tops lilac polls.)
· Maiden’s Blush – single, very fragrant, pink
· Mechta – double-flowered, violet
· Michel Buchner – double-flowered, lilac
· Miss Ellen Wilmott – double-flowered, white
· President Lincoln – single-flowered, very fragrant, blue
· Sensation – single-flowered, purple edged with white
· St. Margaret – double, long panicles, very fragrant, white
· Wedgewood Blue – single-flowered, blue
Other Lilac species and hybrids:
· Josée – a hybrid of S. patula, S. macrophylla and S. meyeri – lavender-pink, dwarf, reblooms from May until frost
· Manchurian Lilac ‘Miss Kim’ (Syringa pubescens ssp. patula) – pink-purple fading to white, fragrant, slow-growing to 8-9 feet
· Meyer lilac ‘Miss Palibin’ (Syringa meyeri) – lavender, very fragrant, 4-5 feet, good hedge
· Prestom lilac ‘Donald Wyman’ (Syringa x prestoniae) – single, reddish-pink, late
· Preston lilac ‘James Macfarlane’ (Syringa x prestoniae) – single, pink, late
· Preston lilac ‘Miss Canada’ (Syringa x prestoniae) – single, pink, late, fragrant