Sometimes in May, the air is redolent with the unmistakably exquisite fragrance of lilacs, for as beautiful as the flowers are, scent is the lilac's most cherished attribute. Of the 20 to 25 species, the common lilac, Syringa vulgaris, has the strongest and sweetest essence, which is richest in the double-flowered varieties. British gardening icon Gertrude Jekyll observed that double flowers are usually sterile, petals having replaced center stamens, and extra petals generate stronger scent. Blooms last longer and retain their fragrance till flowers fade, and doubles are the most consistently fragrant. Some claim white lilacs are not as aromatic as others, but scent is subjective.
Native to the Balkans, these members of the Oleaceae (olive) family came to Europe from Turkey in 1562 and were introduced to the New World by Colonial settlers. Lilac enthusiasts especially revere the heirloom cultivars traceable to the renowned nursery of the Lemoine family of Nancy, France, who, over three generations (from the mid-1800s to early 1900s) hybridized plants, introducing double lilacs and more than 153 named lilac cultivars, many of which are even today considered incomparable. Since the Lemoines' work, the term French lilac has evolved to connote all double-flowering, common lilac cultivars, regardless of origin. The word heirloom is arbitrary, referring to older hybrids of undefined age.
Lilacs blossom late spring through early summer, thrive in full sun in USDA Plant Hardiness Zones 3 to 7, and appreciate some lime in their soil. Newly planted shrubs begin blooming within 2 to 5 years. While they may flower profusely some years and not others, judicious pruning is essential for abundant bloom, shape, vitality, and blossom production.
Lilacs flower on old wood, so they should be pruned immediately after flowering, or else next year's flower buds will be cut off. Remove two-thirds of the suckers and shoots near ground level, keeping a third to mature into future flowering branches. Cut larger stems from the center to allow sun and air circulation to avert disease. Sever awkward limbs to create a well-balanced, rounded shrub. If the lilac is grafted, always remove any shoots arising from the rootstock, below the graft union, to maintain the desired cultivar's flowers. Deadheading spent flowers keeps seeds from forming but is tedious and not absolutely necessary.