Ultimate Guide to Growing Lilac Bush

The lilac bush (Syringa vulgaris) is an attractive deciduous shrub that flowers in mid to late spring. An attractive ornamental plant that thrives in a range of different planting schemes, a lone lilac bush can be used to provide a focal point in the garden. Alternatively, a couple of plants can also be used to introduce loose hedging or privacy to a space.

The plant’s small, fragrant flowers which sit in clusters above the round green foliage, most commonly come in an attractive shade of lilac. However some varieties of the plant also produce their long lasting flowers in shades or white, burgundy, lavender and purple.

Like the forsythia and ash tree, the lilac bush is a member of the Oleaceae or olive family. Growing by 1 to 2 ft a year, when fully mature the plants have a final height of between 8 and 15 ft and a spread of between 6 and 12 ft. They are hardy in USDA Zones 3 to 7.

The fragrant flowers are one of the main draws of the lilac bush. These easy to grow plants can, with a little care, thrive in most gardens.

Ideal for most gardens, smaller cultivars can also be grown on patios or balconies in containers. Elegant and attractive, with the right care these attractive plants can fill your garden with fragrant flowers for many decades.

If you want to add a lilac bush to your garden, this is your complete guide.

Different Varieties of Lilac Bush

There are a number of different varieties currently available. Some of the most attractive and reliable include:

• Miss Kim, a small cultivar which is ideal for foundation planting. A slow growing shrub, when mature Miss Kim enjoys a height of between 5 and 9 ft and a spread of 5 to 7 ft.
• Primrose is a standard sized plant, reaching a height of 10 to 15 ft and a spread of 6 t 10 ft. It produces fragrant yellow flowers.
• Bloomerang Lilac is a dwarf shrub which enjoys a particularly compact growth habit. It has a final height and spread of about 5 ft.
• Wedgewood Blue is another compact specimen. Reaching a height and spread of around 6 ft, it produces attractive lavender blue flower clusters.
• Belle de Nancy produces double pink flowers. When mature it enjoys a height of 8 to 10 ft and a spread of 6 to 8 ft.
• Madame Lemoine is known for its eye-catching, double white blooms. A tall cultivar it can reach a mature height of 15 ft and a spread of around 12 ft.
• Yankee Doodle is a small cultivar grown for its fragrant, rich purple flowers. A cold hardy species it can be grown in USDA Zones 2 and warmer. A mature Yankee Doodle plant has a height of 6 to 10 ft and a spread of about 6 ft.
• Palibin is ideal for ornamental borders and, thanks to its slow growth habit, containers. A Korean variety, it is grown for its purple-pink fragrant flowers. When mature Palibin has a height of around 5 ft and a spread of between 4 and 7 ft.
• Lois Amee Utley is a large variety which produces aromatic pink double flowers. When fully mature the plant has a height and spread of upto 13 ft. The size of Lois Amee Utley means that it is an ideal focal point in a garden. It also mixes well in herbaceous borders.

While most varieties like cooler temperatures, some are suitable for warmer climates, such as USDA Zone 9. Blue Skies, a fragrant cultivar, the elegant White Angel and the hybrid Excel Lilac are some such varieties.

As well as the typical lilac bush flowers, some varieties set white, burgundy or purple flowers.

You can purchase young plants, ready for transplanting, from garden stores and specialist plant nurseries. The latter option often provides a wider range of choice.

You can try growing your own plant from seed. However, germination can be unreliable. It also takes many years for a bush to begin flowering. Most varieties like to enjoy a few years of growth before beginning to set bud. Transplanting young plants provides quicker results.

Where to Position the Plant

These are full sun loving plants, at their best when they receive 6 hours of direct light every day. While this bush can tolerate some shade, too much deters flowering.

Avoid placing the plants near light buildings or walls. Positioning too close to light surfaces causes light to reflect onto the foliage. This can lead to foliage or winter burn.

The lilac bush thrives in well draining neutral soil. The soil should be as rich and as loamy as possible. The plants do particularly well in chalky soil. While the plants can tolerate a clay soil, planting in a heavy soil does stunt their growth habit somewhat.

There are a number of ways you can improve heavy or clay soil before planting. Another easy solution is to plant in a slightly elevated area. This encourages excess water to drain away from the plant.

A full sun loving bush, plant in well draining soil to encourage healthy growth and lots of flowers. 

These plants prefer cool conditions. They often struggle in overly hot or humid areas. In fact too much humidity can cause fungal disease to form.

Finally your chosen position should have some protection from cold winds, which can damage stems and buds. Despite this the lilac bush can tolerate temperatures well below freezing.

Planting your Lilac Bush

The best time to plant your shrub is in early fall, before the ground freezes. You can also plant in the spring either slightly before or just as new growth begins to emerge.

To plant, use a robust shovel to dig a hole in the prepared soil. Ideally, the hole should be twice as large and deep as the current rootball.

Remove the plant from its present container. Carefully brush any remaining soil from the root system and gently tease the roots apart.

Center the plant in the hole. The top of the root system should sit level with the soil.

Backfill the hole. Take care not to compress and compact the soil, this can hamper drainage and cause soil to become waterlogged.

After planting use a hose to soak the soil around the plant.

If you are planting more than one specimen space each bush roughly 5 ft apart. This may seem excessive when planting small specimens, but they will quickly grow and fill the space.

Planting in Containers

The lilac bush isn’t ideal for a container garden. However, smaller and dwarf specimens can be encouraged to thrive, with a little extra attention. If you are growing in a container try dwarf varieties such as Munchkin or Pixie. Some compact cultivars, such as Syringa meyeri and Syringa patula can also be successfully grown in containers.

The plants like lots of room to spread their roots. Select a pot that is at least 24 inches wide and 12 inches deep. The pot should be clean and have drainage holes. You can also add a layer of crocks or pebbles to further improve drainage.

Fill the pot with well draining potting soil and plant as described above.

Caring for a Lilac Bush

Once established these plants are pleasingly low maintenance. Keep the soil weed free. Weeds can harvest moisture and nutrients from the soil, stunting the growth of your plants. There are a number of useful weeding tools that you can use to keep your soil clean and efficient.

Once established these hardy plants need little, regular attention. 

When to Water

In the weeks after planting, try to keep the soil lightly moist. Once the plants are established and new growth is visible, reduce the frequency with which you water.

Only water established plants when the soil begins to dry out. Consequently, you may only need to water your lilac bush during periods of drought.

Be careful not to overwater the plants. Not only can overwatering cause root rot, it may also deter plants from flowering.

Fertilizing your Flowers

This is not a heavy feeding plant. Fertilize once a year in the spring, just as new growth emerges. This is particularly important if you are growing the plants in poor soil. A balanced fertilizer, such as Miracle Gro Water Soluble All Purpose Plant Food, is ideal.

For an additional boost, you can apply a generous layer of organic mulch in the spring. This slowly breaks down enriching the soil and giving the plants a further boost.

 

How to Prune

Annual pruning is vital to prevent problems such as powdery mildew. The best time to prune your lilac bush is just after it has finished flowering for the year. The lilac bush sets its flowers on old wood. Pruning straight after flowering has ended reduces your chances of accidentally removing next year’s buds.

Pruning helps to prevent plants from outgrowing a space. Older plants may require a hard pruning, known as renovation. 

Use a sharp garden scissors to prune the branches. As you prune, try to thin out the growth and improve air circulation both around and through the plant. You can also prune away branches to keep the bush in a manageable shape.

Older shrubs with lots of old, tangled branches may require a more severe pruning. This is known as renovation.

Renovation of older shrubs should be done in the winter, when the plant is dormant. While the lilac bush responds well to hard pruning they won’t flower for at least one year afterwards. This is because the lilac bush sets flowers on old wood. Consequently you wil  have to wait for the stems to regrow before the flowers begin to form again.

To maintain some flowering, instead of a hard pruning in one year remove alternate stems, hard pruning or cutting down to the ground about a third of the plant each year. This form of renovation takes longer but allows the plant to keep flowering, albeit in  a limited fashion.

As well as annually pruning, remove any dead or diseased wood as soon as you notice it. This helps to keep the plant healthy.

Deadhead spent flowers to prevent the seeds from forming and spreading through the garden. Deadheading also helps to encourage a second, later flowering.

Finally, remove any suckers that emerge as single stems near the base of the plant. Cut them down to soil level. The suckers can either be discarded or potted on to produce new plants. .

Overwintering a Lilac Bush

Most lilac bush plants can withstand temperatures as low as -40 ℉. Planting in well draining soil means that frozen water is unlikely to damage the root system. A layer of mulch can provide further protection.

While these are cold hardy plants, they do need protecting from icy winds that may damage the flower buds. Cover the plants with a fleece jacket or blanket such as the Haxnicks Easy Fleece Jacket. This can be removed on warmer winter days. Just remember to recover your plant before the next cold wind arrives.

Propagation Methods

If allowed to, the lilac bush happily spreads through a garden. This helps to make propagation easy. There are a number of different propagation methods you can try.

One of the easiest ways to propagate plants is by root division. Most lilac bush varieties are clump forming. This means that they spread through shoots that extend from the main trunk.

Propagation is easily done by digging down, as deeply as possible, around one of the shoots and severing it from the main plant. Aim to keep as much of the root system intact as possible.

Replant the severed shoot in rich soil, either in the ground or in a pot. Remember to keep the soil evenly moist until new growth emerges.

Taking Softwood Cuttings

Softwood is the current season’s growth. Softwood cuttings are best taken during June or July. Take your cuttings from strong, healthy shoots, these have the most potential to root quickly.

Use a garden scissors to make an incision just below a leaf node. Each cutting should be around 4 inches long. Cut away any foliage from the bottom half of the cutting. You can also cut the remaining foliage in half to minimize water loss.

Dip the cut end of the stem in rooting hormone before planting in a small pot filled with fresh, moist potting soil. The lower leaves should sit just above soil level.

Place the cutting in a propagator or cover with a plastic bag. Use canes to support the plastic bag so that it doesn’t contact the cutting. The Early Grow Domed Propagator has an extendable roof, allowing you to continue providing the ideal conditions for your cutting as it grows and develops.

Put the cutting in a warm position away from direct sun. Keep the soil evenly moist.

To check for root formation gently tug the cutting. If you feel resistance it means that roots are forming. Once new growth is visible remove the cutting from the propagator and allow it to grow on before hardening off and transplanting.

Growing new Plants from Seed

When your lilac bush is in full flower, identify the healthiest blooms. Harvesting seeds from healthy flowers helps to ensure healthy, attractive plants.

Lilac flowers can last for several weeks. Once they wilt clusters of brown, nut like fruit emerge. As these dry they split, revealing seed pods.

To harvest the seeds pull them from the dried pods. They can be stored in a cool dry place until you are ready to sow.

Be warned, if you are growing a hybrid variety propagating new plants from seed should probably be avoided. Hybrid varieties rarely grow true to type and are often disappointing.

Growing from seed is often unreliable. A lengthy process, other forms of propagation are simpler and quicker.

When you are ready to sow the seeds, fill clean seed trays or pots with fresh seed compost and moisten. Sow the seeds as thinly as possible over the surface before covering with a thin layer of perlite or vermiculite.

Some commercially produced seeds may have already been exposed to a period of cold temperatures. Others, including ones you have harvested yourself, will need to be put through this process before they can germinate. Put the trays or pots in a polythene bag and place in the refrigerator for about 3 weeks.

After removing the seeds from the refrigerator, place the trays in a warm position. The temperature should average 64-70 ℉. A heat mat can help you to provide a constant temperature. The Vivosun Heat Mat is not only durable it is also waterproof, meaning you don’t have to worry about any accidents when watering your plants.

Germination can take anything from 14 to 60 days. As the seedlings emerge, increase the ventilation around them.

When the seedlings are large enough to handle, transplant the healthiest specimens into 4 inch pots and grow on in a cool, light position away from direct sun. Remember to harden off the seedlings before transplanting outside.

Common Pests and Diseases

A pleasingly hardy shrub, the lilac bush can withstand most common issues.

Powdery mildew can be particularly problematic during humid summers. While not a fatal issue, it can cause unsightly white powdery patches to form on the foliage of the plant. It can be treated with chemical or organic solutions. One reliable organic treatment is to spray the affected foliage with a liquid solution made up of one tablespoon of baking soda and half a teaspoon of liquid, non-detergent soap diluted in one gallon of water.

Scale, thrips and borers and target the foliage of the plant. Regularly inspect the foliage for signs of infestation. Pest issues can be treated with insecticides or an application of homemade insecticidal soap.

Why is My Lilac Bush Failing to Flower?

Some cultivars won’t flower for upto 5 years after planting. If your specimen is young you may need to wait a few years until it is mature before it begins to flower. Dwarf varieties also like to establish themselves and grow for a few years before flowering.

The lilac bush sets flowers on old growth. Pruning away old growth in the fall can prevent flowers from forming the previous year. Well established plants often have lots of old growth that needs to be pruned away, this is known as renovation. While a harsh pruning may prevent flowering the following year, the plant should quickly recover.

Planting in too shady a position, pest infestations and too little moisture can also inhibit flowering.

Finally, a failure to flower could be caused by over fertilizing. Regularly fertilizing other nearby plants and lawns can cause the lilac bush to take up too many nutrients which may inhibit flowering. Reduce the fertilization of nearby plants and feed your lilac bush a dose of phosphorus rich fertilizer such as bone meal.

When in flower the plant attracts butterflies, birds and pollinators to the garden. A failure to flower could be caused by a number of different, easy to correct issues.

An attractive garden specimen, this plant is a perfect companion to spring flowering bulbs such as daffodils and tulips. Peonies are also a lovely companion. They can also be planted alongside dogwoods, mock orange shrubs, magnolia trees and flowering cherry trees to extend the flowering season from spring until late summer. Taller specimens make ideal natural trellises for light climbing vines such as the clematis vine. Again this helps to extend the flowering season, the clematis begins to flower as the lilac bush fades.

A classic garden plant, the lilac bush works in a range of planting schemes. As popular with pollinators and hummingbirds as it is with gardeners. For many people the low maintenance, long lasting lilac bush is the ideal garden plant.