Syringa vulgaris Seeds | Common Lilac
LATIN NAME: Syringa vulgaris
COMMON NAME: Common Lilac
Plant Profile
The lilac that fills whole streets with scent in May is a Balkan scrub shrub that most gardeners would not look at twice in the wild. There Syringa vulgaris grows as a suckering, thicket-forming bush on dry stony slopes and in open woodland over limestone, with small leaves, sparse trusses and a habit closer to a hazel than to the fat-flowered garden forms. Everything that made it a garden plant came from selection.
Lilac reached western Europe in the middle of the sixteenth century by way of the Ottoman capital, carried in the baggage of diplomatic missions that were also sending bulbs westward to Vienna. From the imperial gardens it passed quickly into the Low Countries, France and England, and within a century it was a fixture of the garden. Even the English name arrived by the same road.
The first sign is usually a shoot that wilts and blackens at the tip while the rest of the bush looks healthy. Cut it out well below the discolouration, into clean wood, and disinfect the blades between cuts. Water at the root rather than over the foliage, keep the base clear so air moves through, and avoid high-nitrogen feeding in spring, which produces soft growth the bacterium exploits.
Lilac carries its share of viruses and phytoplasmas. Lilac ring mottle virus and other graft-transmissible agents reduce vigour and flower quality in old stock, and lilac witches’ broom is caused by a phytoplasma that turns a bush into a mass of thin yellowed shoots. Propagation of high-value clones therefore leans on clean starting material, heat treatment and meristem culture, followed by in vitro multiplication.
Lilac is slow to build a saleable plant from a cutting, and the trade has long budded or grafted it, sometimes onto privet rootstock, which roots easily and grows fast. The drawback is unmistakable later: privet suckers push up from below ground and slowly take the bush over. Own-root plants take longer to size but stay true, and they are what a careful planter should ask for.
Science & Biotechnology
The scent is a mixture rather than one molecule. Linalool, terpineol and the lilac aldehydes and alcohols dominate the headspace of the fresh flower, and the genus also accumulates syringin, a phenylpropanoid glucoside named after the plant, in bark and leaves. Distillation destroys much of the character of the bloom and gives a thin oil, so perfumers build most lilac notes from other materials.
Uses & Benefits
Once in cultivation, lilac proved extraordinarily plastic. Nineteenth-century nurserymen, above all Victor Lemoine at Nancy, raised and named hundreds of cultivars, and the double-flowered sorts that dominate the modern garden descend largely from that work. This is why the plant is still called French lilac in the trade, and why an old garden lilac is usually a named clone rather than a seedling.
A lilac hedge gives scent, cover and cut stems in one investment, and takes clipping well if the trimming is done at the right moment. For the vase, cut the trusses as the lowest flowers open, strip the lower leaves, split the woody stem ends and stand them deep in water. Growers once forced lilac out of season by lifting bushes into a cool house and warming them gradually.
Lilac blooms on wood that is a year or more old, so never cut the bush back in spring or you remove the season’s flowers. Deadhead the trusses as they fade, thinning the shoots at the same time, and take a few of the oldest stems out at ground level each year to keep new wood coming. Remove sucker growth from grafted plants entirely.
Growing from Seed
The commonest serious problem of lilac is bacterial, not fungal. Pseudomonas syringae, which blights many woody plants, causes lilac blight: dark water-soaked patches on young shoots and leaves, blackened flower trusses, sunken cankers on the stems and a dieback that can carry a whole branch down. Cool wet weather in spring favours it, and rain, overhead watering and pruning tools all move the bacteria about.
Seed is the way to raise lilac only if you want variation or many plants cheaply, since seedlings are not true to the parent and will not flower for several seasons. Collect the small flattened capsules from the dried trusses, clean the winged seed out of them and store it cool and dry until winter. A cold spell outdoors is needed before the seed will start, so sow thinly in a pot of loam, leaf mould and sand and leave it in a shaded frame through the winter. Prick the seedlings into deep pots as soon as the first pair of true leaves is open, and plant them out while small.
Our Take
Buy lilac on its own roots if you can, prune it straight after flowering and give it full sun, and it will outlast the hedge around it. Our notes on early lilac and on the late lilac cover the two species that stretch the season at either end, and Syringa pubescens is the smaller Asian species for a tight garden.
Related Reading
More species in the same orbit as Common Lilac: