Common lilac bushes (Syringa vulgaris) are deciduous shrubs that bloom in the late spring. They are part of the olive family, along with other such ornamental plants as ash trees, forsythia bushes, and privet shrubs. The outstanding quality of many lilac varieties is the sweet fragrances of their flowers. The blooms appear in the mid- to late spring in branching clusters, or panicles. Each flower is only about 1/3 inch across. The leaves are gray-green to blue-green in color and reach around 2 to 5 inches long; they do not change color in the fall. And the bark of this shrub is gray to grayish brown. The best time to plant lilac bushes is in the early fall before the ground freezes. They have a moderate growth rate of 1 to 2 feet per year.
|Botanical Name||Syringa vulgaris|
|Common Names||Lilac bush, common lilac|
|Mature Size||8–15 ft. tall, 6–12 ft. wide|
|Soil Type||Loamy, well-drained|
|Flower Colors||Lavender-blue, white, burgundy, deep purple, lilac|
|Hardiness Zones||3–7 (USDA)|
Common lilac bushes are attractive enough to be treated as specimen plants, grown as focal points in the landscape. 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.
Once they’re established, lilacs don’t require much maintenance. They will typically only need watering during prolonged periods of drought, and they prefer annual fertilization. Pruning also is generally an annual task.
Click Play to Learn How to Prune Lilacs
Grow lilac bushes in full sun, meaning at least six hours of direct sunlight on most days. Lilacs will tolerate some shade, but too little light can limit their bloom. They do not do well in full shade.
Lilac bushes prefer a rich, loamy soil with sharp drainage and a neutral soil pH. They can tolerate clay soil, though it can stunt their growth.
Lilacs prefer a moderate amount of soil moisture. But soggy soil can lead to root rot and poor blooms. Water young lilacs regularly to keep the soil lightly moist. Mature plants typically will only need watering during periods of drought.
Temperature and Humidity
Lilacs bushes prefer climates that have fairly cool summers. They are not recommended for hot, humid areas, such as the Southern United States. High humidity can lead to fungal diseases on the plant. Moreover, lilacs can tolerate temperatures well below freezing, though they prefer protection from bitter cold winds, which can damage their flower buds and break stems.
Lilac bushes can benefit from a spring feeding, especially if you have poor soil. However, don't use a fertilizer that's high in nitrogen, which can lead to poor blooming. Instead, use a balanced fertilizer.
There are several types of lilac bushes that vary somewhat in appearance, including:
- 'Wedgewood Blue': This compact lilac variety 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 main species, 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 (multiple layers of petals) 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 lilac variety stands tall at up to 15 feet high 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 still deliver the beloved sweet lilac fragrance. It is suitable for zones 3 through 7.
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, as lilacs bloom on old wood. Prune branches to thin out the growth (for better air circulation) and to keep the height of the shrub 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.
Anyone who has grown lilacs knows how readily they expand and spread. Most lilacs are clump-forming plants that spread via shoots extending from the trunk. To propagate lilacs, simply dig down around one of the shoots and cut it from the main plant, keeping the roots intact. Then, replant the shoot in rich soil wherever you wish, and keep its soil lightly moist (but not soggy) at all times until it's established.
Lilacs are fairly hardy shrubs and can survive most pest and disease problems. However, they are susceptible to several. The fungal disease powdery mildew is commonly seen on lilacs, especially during humid summers. It creates whitish powdery patches on the foliage. There are both chemical fungicides and natural methods for combatting powdery mildew. The disease usually won’t be fatal, but you should still treat your lilac as soon as possible to limit its spread. Common pests that can affect lilacs and damage their foliage include scales and borers. If you spot these tiny insects on the stems and undersides of leaves, treat your plant with neem oil or another insecticide.