Lilacs are beloved old fashioned flowering shrubs grown for their fragrance. Lilac plants come in colors ranging from white to pink, and rich purples, as well as its namesake hue. Syringa vulgaris lent its common name, “lilac”, to a tint of purple that is warmed by red and softly pastel.
Not everyone loves these shrubs. Often maligned as coarse, prone to mildew, and giving only one season of interest, many dislike them. I ignore all such criticism and grow a number of varieties on my large property. The lilacs do require a sizable space in the garden. Calculate my pros and cons to decide whether to add the Syringa ( which one or how many) to your own garden plans.
Mature Size of a Lilac
Planted, they require the space of a small tree.
The usual dimensions of a mature Syringa vulgaris is quite large: typically 16 feet tall by 12 feet wide. Like a small tree, their branches are like small trunks in an older bush.
Varieties differ by several feet in height and width. While it is normal to prune lilacs, they are not hedged or drastically cut back, except to renew.
- Zones: 3 to 7
- Exposure: Full sun
- Soil: well-drained, fertile, humus-rich, best for bloom
- pH: prefers neutral to alkaline (pH 7)
- Water: Average for Eastern and Midwest USA
- Fertilize: in early spring, but don’t over-fertilize
Genus Syringa is in the Oleaceae family, which makes it a relative of Privet, Jasmine, and Olives. There are about 20 to 25 species, natives of woodlands and scrublands of South East Asia and Southern Europe.
These bushes are cold hardy, but not heat tolerant, which is why they aren’t recommended further south than Zone 7. They are not pollution tolerant either, which may result in leaf-roll necrosis in some city environments.
The Look of Lilacs
The bush shape is upright, but spreading, a multi-stemmed shrub or small tree in the landscape. It tends to legginess and densely shades the ground and its neighbors.
The leaves are usually a mid green to bluish green, and heart shaped. Opposite, simple, in structure and type.
The single flowers are born in pyramids of panicles, usually blue-violet to lavender and sometimes pink or white. There is a rare yellow. Each single flower has four petals.
Growing S. vulgaris
Plant container grown lilacs in spring or fall as you would any garden shrub.
Syringa does have some health issues. It is prone to borers and powdery mildew, in particular. Removing affected branches controls borers, and planting in an area with good air circulation help with preventing mildewed leaves.
Choose a spot that has full sun, well-drained soil, and good air flow. Amend soil with compost. Spread wood ashes around the established plant after a few growing seasons.
Propagation of Lilac Bushes
First, lets consider multiplying your Syringa stock. These are large shrubs, but there may be cases where a hedge of them is desired. The easiest way, which I have utilized many times is division.
Home gardeners will always propagate a lilac shrub by division or possibly vegetatively. A shrub grown from seed will take about five years before the first bloom, and the outcome is unknown before that time.
New Plants from Established Lilacs
Lift the plant, cut away unwanted root or branches that are damaged. Afterwards, replant the new start in prepared soil at the same level it originally grew, in the same way most shrubs are planted.
Take a large shovel with a round point and dig into the soil next to the part of the syringa which you wish to portion off. A spud bar will sever the roots from the mother plant. Or you may want a a large lopper to cut the connecting roots.
Growing from Suckers
Simply divide off roots and stems from the mother plant. The new plants will already be about 2-3 feet tall, usually. This is because most lilacs sucker quite readily and new plants are often as easy as digging out some of those offspring.
Suckers are the best way to propagate new lilac shrubs. They grow from the bottom of the plant, and you usually have too many!
Seeds are not a recommended way to increase your stock of Syringa. The resulting plants may not have the desired qualities, and they may take a very long time to come into bloom.
How To Dig Out Your New Plant?
Use this method on any shrub:
- Using a sharp spade dig out the sprouts with as much root as possible.
- Where the large root connects to the mother plant use loppers to easily sever this root.
- Trim off any damaged roots.
- Plant into prepared ground.
- Perhaps trim about a third from top growth.
Time To Propagate
Spring is the best time to dig and divide plants. Usually right before they break dormancy; at least, don’t wait until fully leafed out, or the shock to the plant is too great for good recovery. (Not that you can’t do these things after full growth is underway, it just isn’t best practice for success).
New Shrubs From Cuttings
Since the trunks are almost the size of small trees in older plants, you may want to grow new plants by taking a cutting.
For most people the success rate from cuttings is probably about 50%, so take twice as many cuttings as you think you will need. They should be about 8 inches long, from new growth (these are softwood cuttings). Strip off lower leaves and dip into hormone powder or gel (not absolutely necessary, but it helps).
Quick Clone Gel – 75mL – Most Advanced Cloning Gel for Faster, Healthier, Stronger Rooting Clones.
Place into well draining sterile soil in your containers. Perhaps cover them for a greenhouse effect. Clear plastic works well. Roots should appear about 2 months after this procedure and take about 3 years to bloom.
What Types of Lilacs for the Garden?
The most widely grown are cultivars of Syringa vulgaris, but there are others available.
The Korean Lilac
Syringa meyeri is the Korean lilac. The Korean lilac is fragrant, the leaves and flowers are smaller; but the overall size of the shrub is 8′ by 10′. A popular variety is “Palibin” which is compact growing 4-5 feet tall with a spread of 5-7 feet.
Syringa pubescens subsp. microphylla “Superba”
Known as the “littleleaf lilac”, S. pubescens microphylla, grows 6 ‘ tall by 10’ wide. Features include pink flowers, better resistance to powdery mildew, and profuse bloom.
S. patula ‘Miss Kim’
Compact at 8 to 9 feet, ‘Miss Kim’ boasts fragrance AND a port wine autumn color. Most other lilac leaves simply turn gray and fall. Blossoming about a week after the common S.vulgaris.
Although there are named plants of other Syringa species, few are offered for sale to the general public. Gardeners should choose from the many tried and true variations of the S. vulgaris.
Did You Know?
Use your lilacs to indicate the proper time for sowing seeds in your garden.
- When lilacs leaf out: you can direct sow cool-weather vegetable seeds including peas, lettuce, and spinach; cold-tolerant herbs like parsley and chervil and hardy annuals.
- When the flower panicles are in full bloom, you can direct sow seed of basil, corn, tomatoes, marigolds, and geraniums.