Common lilac bushes (Syringa vulgaris) are deciduous shrubs that bloom in late spring. Syringa is a member of the olive family, along with other such ornamental plants as ash trees, forsythia shrubs, and privet shrubs. The best time to plant lilac bushes in fall, before the ground freezes. They have a moderate growth rate of 12 to 24 inches per year.
The outstanding quality of many lilacs is the smell of their flowers. However, not all types are equally fragrant; grow Syringa vulgaris when in doubt if the scent is your main interest. They are among the most fragrant flowers available to gardeners in cold climates. The smell of Syringa blossoms is one of the most unforgettable aromas of the plant world.
|Botanical Name||Syringa vulgaris|
|Common Name||Lilac bush, common lilac|
|Plant Type||Deciduous shrub|
|Mature Size||6 to 16 feet tall and 8 to 12 feet wide|
|Sun Exposure||Full sun|
|Soil pH||Neutral (pH near 7.0)|
|Flower Color||Lavender-blue, white, burgundy, deep purple, lilac|
|Hardiness Zones||3 to 7|
|Native Area||Southeastern Europe|
Common lilac bushes are attractive enough to be treated as specimens. They are also often planted in rows along property borders and pruned into loose hedges. The 'Miss Kim' cultivar is small enough for use in foundation plantings, as is the even more compact 'Bloomerang' lilac, which is a dwarf shrub.
These wonderful bushes are, unhappily, prone to powdery mildew disease, so be sure to provide good air circulation by keeping their branches pruned. If your lilacs are not flowering, there are some tricks you can try. A frequent problem growers have with common lilacs is that they become too big as the years go by. This happens when you (or the prior landowner) have failed to stay ahead of their growth. But the problem is fixable by trimming the overgrown lilacs, which will also help rejuvenate them.
Click Play to Learn How to Prune Lilacs
Grow lilac bushes in full sun. They will tolerate some shade but bloom best when grown in full sun. They do not do well in full shade.
Lilac bushes prefer a rich, well-drained, loamy soil with a neutral soil pH, but they will still grow in clay soil, just not as well.
Water lilacs fully, but do not keep the soil wet. The roots do best in well-drained soil that does not stay wet. Overwatering will lead to poor blooms. It is fine to mulch around the base of the plant to help retain moisture if desired.
Temperature and Humidity
Lilacs do best in cool-summer climates and up to USDA plant hardiness zone 7. They are not recommended for hot, humid areas, such as southern U.S. states in zones 8 or 9.
Lilac bushes can benefit from a spring feeding, as long as the nitrogen is kept in check. Too much nitrogen in the soil leads to poor blooms.
Varieties of Lilac Bushes and Trees
'Wedgewood Blue': This compact variety of lilac bush attains a height at maturity of only 6 feet, with a spread equal to that. The flowers are contained in thick clusters of lavender blue. It thrives in zones 3 through 8.
'Yankee Doodle': A small lilac bush with deep purple, fragrant blooms, Yankee Doodle is a bit more cold-hardy than the species variety, suitable for zones 2 through 8. It grows 6 to 10 feet tall and 5 to 6 feet wide.
'Belle de Nancy': This variety has double pink flowers and grows 8 to 10 feet tall and 6 to 8 feet wide. It blooms in late spring to early summer and is suitable for zones 3 through 9.
'Madame Lemoine': Blooming with bright white double flowers, this shrub variety stands tall at up to 15 feet in height and 12 feet wide. It is suitable for zones 3 through 8.
'Primrose': Primrose is a standard-size lilac that grows 10 to 15 feet tall and 6 to 10 feet wide. It is notable for its yellow flowers that also deliver the beloved lilac fragrance. It is suitable for zones 8 through 7.
Anyone who has grown lilacs know how they readily they expand and spread. Most lilacs are clump-forming plants that spread via shoots extending from the trunk. To propagate a new plant, simply dig down around one of the shoots and cut it from the main plant, including the roots, then replant the shoot in beneficial soil. Water the transplant dutifully until it is established.
Pruning is critical for lilacs, both to promote flowering and to ensure air circulation to prevent powdery mildew and other problems.
The right time to prune is just after blooming is over, since these are shrubs that bloom on old wood. Prune branches to thin out the growth (for better air circulation) and to keep the height of the plants in check. In addition, cut off the dead flowers when they are done blooming. This will prevent the seed from forming and thereby promote more profuse flowering the next spring.
If you'd like to limit the height of the shrub, cut off stems that are 2 inches in diameter or larger. You can also shape the shrub by trimming smaller stems as needed. The 1/3 rule of pruning shrubs applies to lilac bushes.
Bush Lilac vs. Tree Lilacs
Because of the height of many bush lilacs, people sometimes refer to them as "lilac trees," lumping them in with the other wonderful flowering trees of spring. These plants should not, however, be confused with the true "tree lilacs," that is, Japanese tree lilacs (Syringa reticulata) and Chinese tree lilacs (Syringa pekinensis).
True tree lilacs bloom a bit later than lilac bushes. Their blooms are white, and they are not as aromatic as the flowers of common lilac bushes. But the tree lilacs do have an attractive bark, especially the Chinese tree lilac, which has a shedding bark similar to that of the paper birch.