Like many gardeners, whenever I think of lilacs, my mind is immediately flooded with fond memories of warm late spring days when the air around a lilac bush is heady with delicate perfume, and all seems well with the world. This well-loved genus of deciduous small trees and shrubs, known botanically as Syringa, includes only about 20 species. However, because of its popularity as a garden must-have, much hybridization has been carried out by lilac enthusiasts over the years, resulting in a great number of named cultivars.
The true species are native across a wide range, which means considerable variation in the hardiness of different lilacs. Two lilacs originate from Europe, one in the Himalayas and the others range throughout eastern Asia as far south as Yunnan in China. As for cultural requirements, lilacs prefer a good sunny exposure in well-drained but rich soil. At planting time add a healthy amount of compost to the hole and backfill the soil. In subsequent years add a mulch of compost to the root area about 7 cm (3 in.) deep when the new growth begins to break. Lilacs also prefer their soil to be on the alkaline side. If you live in an area where the soil tends to be acidic, as it is out here on the coast, sprinkle a handful of dolomite lime per square metre or yard around each bush in the fall. Lilacs work well as single specimens in a lawn or courtyard, or they can be incorporated into the back of larger mixed borders with other shrubs or perennials. The common or French lilac, Syringa vulgaris, is one of the best-known lilacs, and coming to us from the higher altitudes of eastern Europe, it is hardy in zones 4 to 8. Its multi-stem habit makes it a great candidate for a hedging screen. At maturity it can reach 7 m (23 ft.) in height. Its foliage is typical of the genus, ovate to heart-shaped, with opposite leaves growing to 10 cm (4 in.), and stems bearing highly scented lilac-coloured flowers that occur in dense conical panicles from late summer to early spring. This is truly the lilac that inspired the classic Ivor Novello song that goes, "We'll gather lilacs in the spring again . . ." Syringa vulgaris has many wonderful cultivars. 'Primrose' is quite striking, with its heavenly scented flowers a pale primrose-yellow, the colour of cream. Another favourite is 'Charles Joly,' which has deep double purple flowers, but for pure-white beauty, look for 'Mme. Florent Stepman.' Other beauties worth mentioning are 'Louis Van Houtte,' 'Sensation' (with wine-coloured blossoms edged in white), 'Angel White' and 'Andenken an Ludwig Späth' ('Souvenir de Louis Spaeth'). Similar to S. vulgaris and also often found in older gardens, Syringa x chinensis reaches a height of about 5 m (17 ft.) with abundant lilac-purple and very fragrant flowers. Good for zone 5 and up. One thing that all true gardeners share is patience, and these lilacs, if purchased as small gallon-container plants, can often take five to seven years to flower. Those new to gardening may throw up their hands in horror when they hear this, but experienced gardeners know this is just part of the charm of gardening, and five years is but a flash in the grand scheme of things. If you simply can't wait that long, you may want to purchase a mature plant in a larger container. Newly planted lilacs should be deadheaded before they have a chance to form seed. This will allow all the energy to go into the production of flowers for the following spring. Also, because this group is multi-stemmed, prune out any spindly stems as you remove the dead flowers. In fact, dead flowers should be removed every year as long as you can reach them. The large group of hybrids that comprises Syringa x hyacinthiflora includes probably the hardiest of all lilacs, being suitable for zones 3 to 7. As the name suggests, most of these plants have much larger showy panicles, resembling the flowers of a hyacinth. Resulting from crossing the Korean species S. oblata with S. vulgaris, this lilac has an upright growth habit when young, but becomes more spreading with maturity. Its leaves are heart-shaped, 10 cm (4 in.) long and sometimes display a bronze hue during the plant's early years. In this group, one notable cultivar is S. x hyacinthiflora 'Blue Hyacinth,' which has large, eye-catching, single lilac/blue flowers with a divine perfume. Equally noteworthy is S. x hyacinthiflora 'Cora Brandt,' with its large (23 cm/9 in.) panicles of double white flowers. Another most attractive - and again reasonably hardy - lilac is Syringa sweginzowii. Native to southwest China, it is more of an upright shrub reaching four metres at maturity. Its leaves are ovate-lanceolate and somewhat thin in texture compared to other lilacs. Its blooms are rather loosely arranged in upright panicles and the individual flowers are somewhat tubular. It has good scent with flowers ranging in colour from pale pink to white. Being hardy in zones 6 to 7, it flowers late spring to early summer.There is another widely grown lookalike of this particular species. Syringa wolfii has delightful pale-mauve blossoms with a heady fragrance and comes to us from Manchuria. Hardy to zone 5. For our readers in colder parts of the province, a truly hardy lilac, Syringa reticulata, native to higher elevations in northern Japan, is suitable for zones 4 to 7. In colder climates this lilac attains a more conical tree-like form with an attractive branching habit, and at maturity it can reach a height of 10 m (33 ft.). However, in milder climates, it isn't as happy and tends to remain shrub-like. Its leaves are lance-shaped to ovate and sharply pointed, and its flowers are creamy-white, scented and borne in large showy panicles when they occur in early to midsummer. If you ever get a chance to visit Ottawa, you will discover some attractively pruned specimens of these trees in the grounds of Rideau Hall. For townhouse gardens, two delightful shrubby forms of lilacs are quite suitable. The lesser-known one, Syringa meyeri, was first collected in northern China in 1908. Forming a dense compact shrub growing to 2 m (6.5 ft.) in height and just over a metre or yard across, it produces somewhat downy new shoots and oval leaves 1 to 3 cm (1/2 to 1 in.) long. Its flowers are bluish-pink small panicles and highly scented. At the UBC Botanical Garden we have several of these planted near our entrance, and in late spring to early summer the air is laden with their luscious fragrance. The other shrubby form, which has received a bit more publicity in recent years, is the dwarf Korean lilac, Syringa pubescens subsp. patula 'Miss Kim.' And I agree, the name is quite a mouthful! As a shrub, it is mound forming and quite similar in proportion to S. meyeri. Its leaves are ovate to elliptic, dull green and 5 to 11 cm (2 to 4.5 in.) long. But 'Miss Kim' boasts the added attraction of leaves that turn purple in the fall before dropping. Its pleasantly scented flowers are borne in erect panicles of pale lilac. While it is lovely, I personally prefer S. meyeri. Both of these shrubby lilacs can get quite large, and having suggested they would be good for townhouse gardens, I would recommend that as the shrubs reach maturity, some thoughtful (but not major) thinning of some of the weaker branches be done right after flowering. On the subject of townhomes, I have a friend who has a gorgeous Syringa vulgaris in a large 1 m (3 ft.) diameter pot on her balcony in Vancouver. It is hopelessly pot bound and full of suckers, yet blooms profusely every spring. She threatens to get rid of it because of the size, but at flowering time each year it gets a reprieve. One last little note of trivia: In cooler parts of the province, as soon as lilacs begin to flower, gardeners know the season is finally warm enough to plant out tender plants such as tomatoes and impatiens. This, of course, provides B.C. gardeners with just one more fine reason to grow the beloved lilac. David Tarrant is a well-known gardening expert, author, and host of Spring, currently on HGTV.