Planting lilacs: when, where & how to plant lilac
Prized for their stunning flowers and attractive foliage, lilacs are a popular garden shrub and tree. Find out all there is to know about planting lilacs and where they grow best.
Widely grown in both public and private gardens, lilacs (Syringa) are a joy to behold from late spring to early summer when they flower. There are many lilac species to choose from, and they come in a range of sizes, making them suitable for almost every garden. Read on to find out how and when to plant a lilac so that it will thrive for years to come.
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Planting lilac: where, when and how
Lilacs are generally easy to grow and care for. However, when planting lilacs, it is important to provide the right conditions including the correct location, aspect and soil type.
Where to plant
Lilacs grow best when they are planted in a position that receives full sun. When it comes to the soil, lilacs prefer a fertile and free-draining soil that is neutral or alkaline, including chalk. With the least hardy lilacs being rated H5 for hardiness, you can expect lilacs to withstand temperatures down to a minimum of -10 to -15 ℃ if the soil is well-drained. Any sites that are prone to waterlogging are best avoided as lilacs struggle when their soil is saturated or overly damp. As tough shrubs and trees, lilacs can cope with either a sheltered or exposed location.
When to plant lilac bushes
If you are wondering when to plant a lilac the answer is either in spring or autumn, when the ground is not frozen. Planting lilacs in spring provides some time for the plant to establish itself before the heat of summer, but frequent irrigation will be required as the temperatures rise. Planting lilacs in autumn is often preferred as the soil is still warm but their moisture requirements are less.
Planting lilacs: how to plant
Before planting a lilac, dig a hole twice as wide and at least as deep as the root ball to prepare the ground. If the roots are bound tightly, gently tease them out to encourage them to make their way into the new soil. Place the lilac plant into the hole ensuring that it is at the same depth it was previously planted. If planting a large and mature lilac, insert stakes to support the trunk with rubber tree ties. Holding the lilac upright, carefully backfill with soil, gently firming in as you go. Water thoroughly and mulch with organic matter.
Planting lilacs step-by-step:
- On a frost-free day in spring or autumn
- Prepare a hole twice as wide and at least as deep as the root ball
- Lower the plant so that it is at the same depth it was previously planted
- Insert stakes if required
- Backfill with soil, firming in gently to remove any air pockets
- Water deeply and keep the soil moist for the first growing season at least
Tip: fertilising lilacs is not strictly necessary. However, you can give them a boost by incorporating some garden compost at the time of planting, especially if the soil is poor.
Planting lilac in plant pots
Planting lilacs in pots is a great way to grow them if you are short on space or your garden has acidic soil, which they do not like. Some types of lilacs can grow very large, including the common lilac (Syringa vulgaris), which can grow to 7m tall, and are best planted directly in the ground. If you want to grow a lilac tree in a pot, a smaller species, such as the Korean lilac (Syringa meyeri), is more suitable. When choosing a pot for a lilac, it is important to ensure that adequate drainage holes are present and that the pot is large enough to support its growth. Generally, a minimum pot diameter of 30 to 60cm is advisable for a compact lilac variety.
Before planting a lilac in a pot, add a layer of gravel to the base of the container to provide some extra drainage. Since lilacs prefer a neutral to alkaline soil, make sure the compost you want to use is within this pH range. For example, you can use our Plantura Organic All Purpose Compost for planting lilacs in pots as it has an ideal pH of 6.5 to 7 and contains the correct nutrients to support the plant’s growth. Lilacs also like a free-draining soil, so add up to 20 to 30% of grit or sand to the compost to further increase the drainage. Plant the lilac at the same depth it was previously and backfill with the compost mix gently firming in around the root ball. Water the lilac in and continue to keep the soil moist but not saturated, especially after planting and during the summer months. A good guide to watering potted lilacs is to wait until the top 2 to 3cm of soil is dry before watering again.
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To help support the lilac’s growth and replenish any lacking nutrients, repot your lilac every 2 to 3 years or before if it has become rootbound. Choose a new pot that is one or two sizes larger, fill with new compost and repot using our planting instructions above. Make sure to water it in well!
Lilac companion plants
Requiring full sun and a free-draining neutral to alkaline soil, lilac companion plants include those that also thrive in the same growing conditions. Here are a few plants that you can grow alongside lilacs:
- Forsythia (Forsythia sp.)
- Hardy geraniums (Geranium sp.)
- Iris (Iris sp.)
- Laburnum (Laburnum sp.)
- Peonies (Paeonia sp.)
Transplanting lilacs
If you need to transplant a lilac, you are best off moving it in spring or autumn. However, it is not easy to successfully transplant a large lilac as the root ball can be considerably large. To transplant a lilac, prepare the new hole first so the lilac can be moved immediately on lifting. Using a spade, dig around the lilac and dig out as much of the current root ball as possible. Place on a tarpaulin and transfer to the new hole. Plant at the same depth it was previously planted. Stake, if necessary, water in and irrigate for 2 to 3 years to help it re-establish.
Pruning lilacs is essential to keep them healthy and ensure that they flower well in late spring. Learn how and when to prune lilacs in our separate article.
