There are few better moments in a British garden than standing beside a lilac in late May, the whole shrub buzzing with bees and the scent carrying right across the lawn. Lilacs are tough, long-lived and, once settled, remarkably undemanding. Most disappointments come down to one of three things: too much shade, planting too deep, or pruning at the wrong time of year. Get those right and you will have a shrub that flowers reliably for decades.

What follows is the basics for a first-time grower — what to buy, where to put it, how to plant it, and what to do in the first year or two.

Choosing the right lilac

Almost all garden lilacs are forms of Syringa, and the choice comes down to size and flowering time as much as colour.

The classic common lilac, Syringa vulgaris, and its many named cultivars are the ones with the big, dense, heavily scented trusses in May. They are also the biggest, often 3m to 4m tall and nearly as wide, and they can sucker. Good named varieties include the deep purple 'Charles Joly', the double white 'Madame Lemoine' and the pinkish-lilac 'Katherine Havemeyer'. If you fancy something unusual, 'Sensation' has purple flowers edged in white.

It is worth seeing a lilac in flower before you buy one, if you can. Colour on a label is a poor guide: whites are creamy in bud and open pure white, 'Charles Joly' is closer to claret than purple, and a shrub sold simply as "lilac" can be anything from pale blue-mauve to deep plum. Flowering time also varies by a fortnight or more between varieties, so if you have room for two, choosing an early and a late cultivar will stretch the display across six weeks rather than three.

If space is tight

  • Syringa meyeri 'Palibin' — compact and rounded, to around 1.5m, with small lilac-pink trusses in late spring.
  • Syringa pubescens subsp. microphylla 'Superba' — dainty rose-pink flowers, strongly scented, often continuing into summer.
  • Syringa patula 'Miss Kim' — neat and upright, later to flower, with decent autumn colour.
  • Syringa x persica — the Persian lilac, finer-leaved and slightly earlier, useful where a border is narrow.

Two practical points when buying. Ask whether the plant is grafted or grown on its own roots: grafted lilacs often throw suckers from the rootstock, and those suckers will not be the variety you paid for, so pull them off. And remember that bare-root plants are cheaper and establish very well when planted in autumn or early winter, while container-grown plants can go in at almost any time, provided the ground is neither frozen nor waterlogged.

A third point that is easily overlooked is size at purchase. Lilacs are sold from a small two-litre pot with a single stem up to a hefty ten-litre shrub already a metre tall. The larger plant flowers a year or two sooner, but it costs a great deal more and often sulks for a season while it settles. A modest, well-rooted plant put in properly in autumn will usually have caught up within three or four years.

Where to plant

Full sun, ideally six hours or more. Lilacs will grow in light shade but flower far less freely, and the scent is weaker.

Soil matters less than drainage. Lilacs are happy in neutral to slightly alkaline ground and will also cope with mildly acid soil, but they hate sitting wet. If your soil is heavy clay, work in grit and plenty of well-rotted organic matter, or plant on a slight mound so surplus water drains away from the roots rather than pooling around them. Waterlogged roots in winter are a far more common killer of young lilacs than cold.

When the position is right, give the plant room. A common lilac needs 3m to 4m in every direction, so keep it well clear of fences, paths and the crowns of neighbouring shrubs. Good air movement around the foliage also helps keep powdery mildew at bay later in the season.

Finally, plant it somewhere you will walk past it. A lilac at the far end of a garden is a lilac you smell twice a year; one beside a path, a gate or a bench gives you the scent every warm evening through its season.

How to plant

Dig a hole roughly twice the width of the rootball and no deeper than the plant was growing in its pot. Fork the base to break up any pan, and if the soil is poor, mix a bucket of well-rotted compost or garden compost into the backfill. Do not add fertiliser at this stage — it encourages soft growth that the plant does not need while it is establishing.

Set the plant in so that the soil mark on the stem sits level with the surrounding ground. This is the single most important moment: bury the stem even a few centimetres too deep and the plant will sit and sulk for years, flowering poorly or not at all. Fill in, firm gently with the heel in stages to remove air pockets, and water thoroughly — a full watering can or two, not a splash.

Finish with a mulch of well-rotted organic matter, 5cm to 8cm deep, pulled clear of the stem so it does not rot the bark. On an exposed site, or with a tall bare-root plant, a short stake for the first season is sensible; remove it after a year so the trunk can thicken and move with the wind.

Pruning: the one rule that matters

Lilacs flower on growth made the previous summer, which means the buds for next May are already forming by July. So prune immediately after flowering, in June, and not a day later than mid-July. Cut the spent trusses back to a strong pair of leaves or a side shoot. This tidies the shrub, stops it wasting energy on seed and encourages fresh growth that will carry next year's flowers.

The classic mistake is to tidy the shrub in late winter or early spring while it is bare. You will cut off every flower bud and get nothing but leaves. If your lilac has grown too tall and leggy, renovate it over three years rather than all at once: each June, take out a third of the oldest, thickest stems at the base, working round the shrub until it has been entirely renewed.

Suckers are best pulled off by hand, tearing them away from the root rather than cutting them, which only encourages more. On grafted plants, deal with them as soon as they appear.

Feeding, watering and the first year or two

A new lilac needs watering properly through its first summer, especially in a dry spell — a deep soak once a week is worth more than a daily sprinkle. After that, established plants in open ground rarely need watering at all.

Feeding can be light. A handful of blood, fish and bone scattered around the root zone in early spring, plus a mulch of compost, is plenty. Avoid high-nitrogen feeds, which produce a leafy, floppy shrub with few flowers. A little sulphate of potash in late winter suits lilacs on thin or sandy soils.

Pests, diseases and common complaints

Lilacs are relatively trouble-free, but a few things are worth recognising.

  • Powdery mildew — a grey-white film on the leaves in late summer. Usually cosmetic on older shrubs; improve air circulation and avoid drought stress.
  • Lilac leaf miner — blotchy brown patches on the leaves from midsummer. Rarely serious; pick off and bin affected leaves.
  • Aphids and scale — watch for sticky honeydew and sooty mould. A strong jet of water or a soap spray usually deals with them.
  • Lilac blight — sudden shoot dieback in wet springs. Prune out affected growth well into clean wood and bin it, do not compost it.
  • No flowers at all — almost always shade, deep planting or badly timed pruning.

Lilacs in pots

If you garden on a patio or only have a balcony, the compact cultivars will happily grow in a container for years. Use a loam-based compost such as John Innes No 3, which holds on to moisture and nutrients far better than a peat-free multipurpose mix on its own. Repot every second or third spring, refresh the top few centimetres of compost each year, and water and feed more diligently than you would a plant in the ground.

Common mistakes at a glance

Sun, shallow planting, and pruning straight after the flowers are the whole secret. Everything else is patience.
  1. Planting in shade and expecting the flowers of a sunny border.
  2. Burying the stem deeper than it was in the pot.
  3. Pruning in winter or early spring.
  4. Leaving grafted suckers to take over.
  5. Feeding heavily with nitrogen and getting leaves instead of scent.

Give a lilac the right start and it will ask almost nothing of you afterwards. Plant it well this autumn, keep it watered through its first summer, and then leave it alone to do what it does best — filling the garden with scent on a warm evening in May.

Photo: Ramon Perucho / Pexels