Common lilac

Common lilac: how do you recognise it?

Habit

Upright, often multi-stemmed shrub of 3–6 m that produces suckers.

Leaf

Opposite, heart-shaped to oval, 5–12 cm, untoothed and hairless.

Bark

Grey, becoming furrowed with age.

Flower

Large panicles of fragrant flowers in lilac, purple or white (May).

Fruit

Brown capsules that stay on the shrub for a long time.

Difference from Indian bean tree

Indian bean tree has much bigger leaves and white flowers in July.

Flowering: April–May · Harvest and fruit: April–May · Pruning: May–June

Identify by feature: Heart-shaped leaves · Purple or blue flowers

Looks like it, but isn’t

• Indian bean tree Catalpa bignonioides: much bigger leaves and white flowers in July. Difference from Indian bean tree

Why grow it?

• Large, heavily scented flower panicles in May.
• Lovely as a cut flower: a few branches scent the whole house.
• Tough, hardy and undemanding.
• Butterflies and bees visit the flowers.

Common lilac: where does it grow best?

• Full sun: in shade it hardly flowers.
• Ideally chalky, free-draining soil; no wet feet.
• Allow 3 m width, and take the suckers into account.
• Lovely as a specimen, at the back of a border or in an informal hedge.

Light

Full sun

Legal basis

Any garden soil

Moisture

Normal

Size

6 m tall, 3 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Mock orange: Flowers shortly after the lilac, also with a gorgeous scent.
• Weigela: Flowers in May–June in pink and red, next to the lilac panicles.
• English lavender: A low, sunny foreground that also likes chalky soil.

Good and bad companions

Best kept away from

• Walnut releases juglone, to which this plant is sensitive: walnut

Common lilac: when and how to plant it?

1. Plant from October to March, root-balled or container-grown.
2. Dig a generous planting hole and mix in some compost; on acid soil you can scatter a little lime.
3. Plant at the same depth as before; on a grafted lilac, keep the graft union above the ground.
4. Water generously after planting, and in dry spells during the first year.

Care

Watering

In dry spells during the first year; rarely after that.

Feeding

A little compost in spring; too much nitrogen gives lots of leaves and few flowers.

Faded flower heads

Cut them off right after flowering, so the shrub doesn’t put energy into seed.

Suckers

Cut or pull them off at the base. On a grafted lilac they come from the rootstock and flower differently.

Tip: Cut branches for the vase in the morning, when the panicle is half open, and strip off most of the leaves: they will last longer.

Common lilac: when to prune it?

Pruning months: May–June.

When: Straight after flowering (May–June).

How:

• Cut off faded flower heads to just above the first pair of buds and remove suckers.
• Every few years, remove one of the oldest stems at ground level, so the shrub stays young.
• Rejuvenate an old, bare lilac over three years: each year, cut a third of the oldest stems down to near the ground.

Caution: Don’t prune in winter or early spring: you would cut off that year’s flower buds.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Suckers

In autumn, separate a rooted sucker and replant it elsewhere. This only works on a lilac on its own roots; otherwise you get the rootstock.

Softwood cuttings

Young, still soft 10 cm shoots root in June under glass or plastic, though not always.

Common lilac: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• The flower buds for May are already on the branches in winter: so don’t prune in winter.

Diseases and pests

• Poor flowering: Too much shade, too much fertiliser or pruning at the wrong time. Give it sun, less nitrogen and prune only after flowering.
• Lilac leaf miner: Brown blotches and rolled-up leaves in summer, caused by the caterpillars of a small leaf-mining moth. Remove affected leaves; the shrub suffers little.
• Powdery mildew: White coating on the leaves in late summer; mainly a cosmetic problem.
• Lilac blight: Young shoots and flower buds turn black and wilt in a wet spring. Cut them back into healthy wood and disinfect your secateurs.

Through the year

• March: Add some compost; planting is still possible.
• April: Flower buds swell; remove suckers.
• May: Flowering: cut branches for the vase. Straight after flowering, remove the faded heads.
• June: Last pruning month: faded flower heads, old stems and suckers.
• July: The new flower buds are forming: no more pruning.
• August: Watch for powdery mildew and lilac leaf miner.
• October: Planting and transplanting suckers.
• November: Planting.

What can you use it for?

Garden and landscape

Fragrant spring-flowering shrub; the flowers are lovely for cutting.

For wildlife

Butterflies and bees visit the flowers.

Edible and useful

Flowers (April–May)

Pick the flowers on a dry, sunny morning in April and May, when the clusters have just opened and smell strong. Older flowers that are turning brown are bitter and almost scentless. Cut whole clusters and pull the florets off with your fingers at home. Use only the little flower tubes, without the green calyx and stalks, which taste bitter. Shake them to remove insects and preferably do not rinse them. The taste is floral with a bitter aftertaste: try a very small amount first, and leave plenty of flowers for the bees and butterflies.

Storing

Fresh flowers keep for one day at most in a closed box in the fridge, so process them quickly. They can be dried in a thin layer on a cloth or rack somewhere airy and shady (3–5 days), but the scent and colour fade a lot. Syrup and sugar keep for six months, vinegar for a year; see the recipes.

Caution: Use only the flowers, and in small amounts: do not eat leaves, twigs, bark or seed capsules. Some people react to the strong scent or the pollen; try a very small amount first. Do not confuse lilac with other shrubs or climbers with white or purple clusters, such as privet (Ligustrum), whose berries are poisonous, or wisteria (Wisteria), which is poisonous. Lilac flowers have four petals at the end of a narrow tube and a sweet, floral scent; wisteria has pea-like flowers in hanging clusters. Do not pick from sprayed shrubs, beside busy roads or where dogs go, and ask the owner for permission. Never eat anything you have not identified with certainty.

Eating and using is at your own risk: see the terms of use.

Recipes

• Lilac syrup (Syrup · ± 600 ml · 30 min + 24 hrs steeping)
• Lilac sugar (Other · ± 250 g · 10 min + 2 weeks)
• Lilac vinegar (Vinegar · ± 500 ml · 10 min + 2 weeks)
• Shortbread with lilac sugar (Dish · ± 20 biscuits · 40 min + 30 min resting)

Good for wildlife

Butterflies

Nectar for butterflies.

Bees

Nectar and pollen for honeybees and wild bees.

Bumblebees

Nectar and pollen for bumblebees, also from deep flowers and early in spring.

Did you know?

• Produces lots of suckers; cut them off to keep the shrub in shape.
• The colour lilac is named after the flowers of the lilac.
• Lilac reached Western Europe in the 16th century, by way of Constantinople.
• Lilac comes from the Balkans. Tradition has it that the Flemish diplomat Ogier Ghiselin de Busbecq brought it from Constantinople to western Europe in the 16th century.
• The genus name Syringa comes from the Greek syrinx, ‘pipe’ or ‘flute’: the hollow or pithy shoots of some species were made into pipes.