How to grow lilac
With beautiful flowers and a beautiful scent, it’s easy to see why lilac is such a well-loved plant. Lilac, or Syringa, is a small tree or shrub with lots to offer. Lilacs are easy to grow and need little maintenance, producing an abundance of compact heads of purple, white, yellow, pink or burgundy flowers every spring, and year after year.
Types of lilac to grow
Lilac belongs to a small genus called Syringa. It contains just the following officially recognised species:
- Syringa emodi. Himalayan lilac. Silver-grey bark with stems growing to 5m (15') in height, and 4m (12') across. Deciduous, with flowers that are purple, pale lilac or white and appear from May to June.
- Syringa josikaea. Hungarian lilac. Can grow to 4m (12'). Dark pink flowers and strongly fragranced.
- Syringa komarowii. Nodding lilac. Can reach 6m (19') in height. Pink or mauve flowers which attract bees, birds and butterflies.
- Syringa oblata. Early blooming lilac, or broadleaf lilac. Very similar to Syringa vulgaris, except that the purple, lilac or white flowers are produced earlier. Oblata refers to the leaves of this species, which are slightly wider than those on other lilacs. Grows to 5m (15').
- Syringa oblata subsp. dilatata. Korean early lilac. As for Syringa oblate, except that this subspecies provides leaf interest too. Young leaves are bronze, they mature to green and eventually turn to purple.
- Syringa pinetorum. A bit of a rarity and seldom seen in the United Kingdom. Can reach up to 3m (9’) in height. Red or lilac flowers appear from May to June.
- Syringa pinnatifolia. The leaves of this species are a little different to other lilacs - they look like those of an ash tree. Can grow to 4m (12’) in height. White flowers from May onwards.
- Syringa pubescens (also known as Syringa meyeri). Growing to 6m (19'), although smaller growing varieties are available. Strongly scented.
- Syringa reticulata. Japanese tree lilac. The largest of Syringa species, this one can grow up to 15m (49'). White or cream flowers with a strong aroma.
- Syringa tomentella. Can reach 7m (21’) in height and flowers in June and July.
- Syringa villosa. Villous lilac, late lilac. Flowers slightly later than Syringa vulgaris, and is not as tolerant of dry conditions as other species of lilac.
- Syringa vulgaris. Common lilac, or ‘pipe privet’. Often grown as a large shrub or multi-stemmed tree with grey bark. It can grow to 7m (22') in height, although there are many cultivars which have been developed to grow to a much smaller plant at full maturity. A strong sweet scent.
There are also several Syringa hybrids which combine different characteristics of some of the species listed above.
What you’ll need to grow lilac
Purchasing a pot-grown lilac is a quick way to add the plant to your garden. Use a spade to dig a hole larger than the rootball. Remove the lilac from the pot and place it in the hole so that the top of the rootball is level with the ground. Backfill with soil, firm in, water well and then mulch.
Propagating from an existing plant is another way to obtain a new lilac. There are several different methods for doing this:
- Softwood cuttings - taken in early summer
- Layering - done in early summer
- Grafting - started in the winter
- Chip budding - started in the summer
Softwood cuttings are by far the easiest and quickest way to propagate a new lilac plant:
- Identify a healthy new shoot which is about 7cm (3") long.
- Using sharp secateurs, remove the shoot from the main plant, cutting just above a set of leaves.
- Remove the small section of stem as far up as the first set of leaves, cutting just below those leaves.
- Remove all leaves from the shoot apart from those at the top.
- Fill a 9cm (3") pot with cutting compost, such as Levington® Peat Free Seed and Cutting Compost.
- Dip the bottom of the shoot into a proprietary hormone rooting powder. This is optional and will help the cutting to put on new roots, but is not essential.
- Insert the cutting into the compost.
- Cover the pot with a clear plastic bag, making sure that it does not touch the cutting.
- Place pot in a warm, light position and wait for the cutting to root and show signs of new growth.
Lilac can be grown from seed, however it takes a lot longer, and is not widely available to buy. Seed can be collected from an existing plant, but allowing an established lilac to produce seeds means that it will slow down in producing flowers. Follow the steps above to produce your own lilacs cheaply and simply.
Where to plant and grow your lilac
Lilacs need well-drained soil and full sun for at least six hours of the day. They are hardy in cold weather and will thrive on chalky and alkaline-neutral soils.
Although considered only a 'small' tree, some lilacs can still reach quite a height. There are many cultivars available, so check that the eventual height and spread is suitable for the size of garden.
Given the glorious scent of lilac, it’s worth putting it close to somewhere that the sweet smell can be appreciated. In a border next to a patio or bench, with a cascade of smaller plants with blooms of a similar colour in front, can create a dreamy oasis in which to relax. If space is in short supply, lilacs can also be grown in containers.
Caring and nurturing for your lilac
Lilacs have no essential maintenance needs, but there are some activities which can help them look their best.
Keep the lilac abundant in flowers by removing any blooms which have started to die back. This deadheading will encourage the growth of new flowers. Flowers can be cut and brought into the home to add fragrance and colour.
Pruning woody growth keeps the plant in good shape and at a manageable size. This should be done in the winter, when the plant is not actively growing. Lilacs can tolerate hard pruning, however they flower on old wood, so remember that removing some of the old wood will reduce the amount of blooms that appear. A way around this is to prune some stems one year, and the rest the following year. Prioritise removing dead, diseased or dying branches.
Mulch the base of the plant each year in the spring to reduce competition from weeds. If the soil is slightly acidic, add lime after flowering to provide optimum growing conditions for the lilac.
Water container-grown lilacs in very dry periods.
Common pests and diseases with lilac
Several pests and diseases can present a challenge to a lilac plant…
A disease of many woody plants, this devastating disease can kill lilac. Look out for limited flowering, bleeding of the stem, and mushrooms around the base in the autumn. There is little treatment for honey fungus - remove and destroy all parts of the plant.
This causes leaves to distort and drop off. Blossoms may be affected and brown prematurely. Maintain good air circulation throughout the plant, pruning if needed to achieve this. Alternatively prevent by spraying with copper fungicide before symptoms develop.
Lilac leaf-mining moth
Caterpillars of this pest feed on lilac leaves, creating unsightly brown blotches on the leaf, which then curl up. It is most noticed from June to September, and is best managed by encouraging birds to visit the garden as they will predate the caterpillars.
This is a fungal disease which can create a dusty white coating on any part of the plant, although is most noticeable on green leaves. Most active in the spring, it is unattractive and can reduce the vigour of a lilac. Prune in the winter to ensure good air circulation around the plant.