Lilac (Syringa vulgaris) reaches 2.5 to 5 metres if it is left to grow freely, flowers in May and June and wants soil with a pH around 7. Two questions decide whether you end up happy: is the shrub on its own roots or is it grafted, and when in the year do you prune it. The first governs what the suckers turn into, the second whether it flowers next year.
Own roots or grafted decides what the suckers are
Lilac throws up shoots from the roots, and no amount of care will stop it. Whether those shoots become a problem depends on how the plant was propagated.
A lilac on its own roots, usually sold as own-root, is propagated from cuttings or layers. Root and top are the same variety, so the shoot a metre out from the stem becomes the same lilac as the one you planted. Dig it up with its roots and move it, and the new plant flowers after 4 to 5 years.
A grafted lilac is a named cultivar joined to a rootstock from another plant. Above the graft union sits the cultivar you paid for. Below it sits the rootstock. The suckers come from underneath, so they are not your cultivar. They flower in a different colour or not at all, and they grow more strongly than the cultivar above, so leave them standing and the rootstock takes over the shrub within a few years. Most named cultivars in the trade are grafted.
Scrape the soil away from the base of the stem. A graft union shows as a swelling or a kink on the stem, at or just below soil level, and everything coming up below it is rootstock. If leaf shape or flower colour on the suckers differs from the shrub in the middle, they come from the rootstock.
Remove the suckers without getting more
Do not cut the shoots off at ground level. The cut leaves the base behind with dormant buds, and it answers with two or three new shoots.
Tear instead of cutting: dig down to where the shoot is attached to the root and pull it loose downwards, so the whole base comes away with it.
Timing: from midsummer onwards, when the shoots are 20 to 40 cm and still soft where they are attached.
How often: one round in June and one in August is enough for an established shrub.
Prune after flowering, not in spring
Lilac flowers on last year's wood. The buds for next year's flowers are laid down over the summer, in the weeks after this year's flowering has finished, and then sit ready on the branch all winter. Prune in March or April and you take off buds that are already set, and the shrub stands green and flowerless in May. That is the most common reason a healthy lilac stops flowering.
The window is short. Prune within two to three weeks of the last flowers fading, so in June or the start of July depending on how far north you garden. Prune in August and next year's buds are already in place, and you remove them all over again.
Start with the faded flower clusters. Cut each cluster just above the topmost pair of leaves, where next year's shoots break out. Up to 2 cm thick, a pair of secateurs is enough. Thicker branches you take with a pruning saw.
Soil, lime and position
Lilac wants a pH around 7 and tolerates soil more chalky than that. Where rhododendron and blueberry thrive on their own the pH is often below 5.5, and there the lilac grows weakly and flowers sparsely. Measure with a soil test and lime if the value is under 6.5. The ground also has to be well drained, because root rot in wet soil makes an established shrub stop flowering. Less than six hours of direct sun a day gives fewer and smaller flower clusters.
How to plant the lilac
Pick the time: April to May or September to October.
Keep the distance: 3 to 4 metres between shrubs and at least 2 metres from a house wall.
Dig wide, not deep: the hole should be twice as wide as the root ball and just as deep. The roots grow sideways.
Set the plant at the right depth: an own-root lilac can go 5 cm deeper than it stood in the pot. If it is grafted, the graft union has to stay above soil level, so you can see where the boundary runs when you clear suckers.
Water and mulch: 15 to 20 litres straight away, then once a week during dry spells the first summer. Lay 5 cm of bark mulch over the root zone, keeping 10 cm clear around the stem.
Why the newly planted lilac does not flower
A newly planted lilac rarely flowers for the first 2 to 3 years. The plant puts its strength into the roots, and feeding does not speed that up. If it takes longer than that, the cause is usually one of these.
Too little sun: a lilac shaded by a tree that has caught up with it stops flowering gradually, not in a single season.
Too much nitrogen: lawn feed that ends up in the border gives leaves instead of flowers. Keep a 1 metre margin when you spread it.
The rootstock has taken over: on a grafted plant where the suckers have stood for five years, what you see growing is usually the rootstock.
Renovate an old lilac over three years
A lilac that has stood for 20 years often carries its flowers three metres up with bare stems below. The shrub is built from several stems out of the base, and that makes it possible to take it down without giving up all the flowering at once.
Year 1: saw out a third of the stems, the thickest and oldest, down to 5 to 10 cm above the ground.
Year 2: take half of the old wood that is left.
Year 3: take the rest. Now the shrub stands entirely on new wood.
Thin the regrowth: every cut stem sends up five to ten shoots. Keep three to four of the strongest per stump.
This is the one occasion when you prune lilac in winter. Work in February or March while the shrub is leafless. The two thirds still standing flower in the meantime. Take the whole shrub down at once, which does work on a dwarf lilac, and you get 1 to 2 years without flowers.
Common lilac, named cultivars and dwarf lilac
| Group | Species or cultivar | Height and width | How you use it |
|---|---|---|---|
| Common lilac | Syringa vulgaris | 2.5-5 m tall, 2-3.5 m wide | Free-growing shrub or boundary. Here the suckers are an advantage |
| Named cultivars | Cultivars of Syringa vulgaris, for example 'Sensation' and 'Charles Joly' | Around 4 m tall and 4 m wide | Specimen with a set colour or double flowers. Usually grafted |
| Dwarf lilac | Syringa meyeri 'Palibin' | 1.2-1.8 m tall and just as wide | Container, low divider, small gardens |
Width decides the choice, not colour. A named cultivar standing 1.5 metres from the path will be cut back every year. If the lilac is to be a loose screen towards the neighbour, common lilac fills the gaps on its own, and we compare more options in the article on planting a hedge.
The scent, the butterflies and what grows under the shrub
The scent is strongest during the first warm days and evenings of flowering. The flower is narrow and tubular with the nectar at the bottom, which makes it easiest to reach for insects with a long proboscis. Lilac draws in butterflies, moths and bees. Flowering is over in June, so if you want butterflies in July and August something has to take over. Summer flowers from seeds for pollinators cover the gap, and the full season plan is in the article on creating a butterfly garden. For scent later in the summer, plant honeysuckle.
The soil under an established lilac is dry and full of roots, so most of what you plant there gets crowded out. Flower bulbs cope best, because they flower and draw the nutrients back into the bulb before the lilac comes into leaf in May.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-03