How to Grow and Care for Lilac Bushes

Common lilac bushes (Syringa vulgaris) are deciduous shrubs native to Europe that can grow as bushes or trees. The Syringa genus includes 12 species of flowering woody plants in the olive family. These are all known as lilacs.

The outstanding quality of many lilac varieties is the sweet fragrance of their flowers, which bloom in spring. The flowers come in an array of colors, including magenta, purple, white, and shades of green and reach around 2 to 5 inches long; they do not change color in the fall. While the blooms only last a few weeks, they will appear again next year.

Common lilac bushes are attractive enough to be treated as specimen plants, grown as focal points in the landscape.

Lilac Care

Once they’re established, lilacs don’t require much maintenance. Adhering to a few important needs will enable them to thrive.

• Plant in full sun with well-draining soil.
• Water during prolonged periods of drought.
• Feed annually with a balanced fertilizer that is not high in nitrogen.
• Space properly when growing multiple bushes and prune yearly.
  

Light

Plant 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.

Soil

Lilac bushes prefer rich, loamy soil with sharp drainage and a neutral soil pH. They can tolerate clay soil, though it might stunt their growth. Compost can be added in the spring to balance soil that is low in nutrients.

Water

Lilacs like a moderate amount of soil moisture. But soggy soil can lead to root rot and poor blooming. 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.

Fertilizer

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, following label instructions.

Types of Lilac

There are several types of common lilac bushes (Syringa vulgaris) that vary somewhat in appearance, including:

• 'Miss Kim' (Syringa pubescens subsp. patula) : This cultivar is small enough for use in foundation plantings. It keeps its natural shape even as it produces a bold showing of flowers.
• Japanese Tree Lilac (Syringa reticulata) : A tree-form lilac, this variety features panicles of white flowers ranging from 6 to 12 inches in length.
• 'Wedgewood Blue' (Syringa vulgaris) : 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' (Syringa vulgaris) : 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' (Syringa vulgaris) : 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' (Syringa vulgaris) : 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' (Syringa vulgaris) : 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

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 flowering is over, as they bloom on old wood. Prune lilac branches to thin out the growth (for better air circulation) and to keep the height of the shrub in check. Cut the oldest branches to the ground, as they won't be strong flower producers anymore, but don't take off more than a third of the total branches. Over-pruning may result in failure to bloom. Also, prune any weak or damaged branches.

Propagating Lilacs

Lilacs readily propagate through many methods, including cuttings, grafting, air layering, and seed. But the best and simplest method to propagate lilacs is by offshoots. This is an inexpensive way to gain a new lilac bush and also prevents the existing lilac from becoming overcrowded. To propagate lilacs from offshoots, follow these steps.

1. Wait until the morning when the temperature is cooler and the plant is hydrated.
2. Dig down around one of the shoots and cut it from the main plant, keeping the roots intact.
3. Replant the shoot in rich soil wherever you wish.
4. Keep its soil lightly moist (but not soggy) at all times until it's established.

Propagate in late spring to early summer to give the shoot enough time to become established before cold weather sets in. 

Common Pests & Plant Diseases

Lilacs are fairly hardy shrubs and can survive most pest and disease problems. However, they are susceptible to a few.

Powdery mildew is a fungus that affects lilacs resulting in white patches on their foliage. Use natural remedies or chemical fungicides to address the problem. Although it's usually not fatal, it's important to address it as soon as possible to keep it from spreading.

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.

How to Get Lilacs to Bloom

Lilacs generally bloom in the mid-to-late spring, though the exact timing can differ based on the variety. The conical clusters of tiny four-lobed flowers have an exceptionally sweet fragrance. The blooms only last for a couple of weeks, but they should readily rebloom each year on a healthy plant. Deadheading, or removing the spent blooms, isn't necessary. To enjoy a longer blooming period, consider planting multiple lilac varieties that flower at different times.

A lack of sunlight is often the reason for poor flowering on a lilac. Watch your lilac for a full day to make sure it isn’t in the shade for any prolonged stretch. Lightly moist soil also encourages a stronger bloom. Mulch around the shrub can help to retain soil moisture and suppress weeds that might compete with the lilac.

Common Problems With Lilacs

Lilac shrubs are typically not problem plants in the garden. But they can encounter a few common issues.

Poor Flowering

If your lilac's rate of flowering has decreased, do a rejuvenation pruning. Remove a third of the oldest branches immediately after the blooming period. In the next growing season, remove half of the remaining old branches after flowering. In the next year, remove any remaining old branches. New branches that flower more vigorously will replace them in a few years.

Leaves Turning Brown

If your lilac leaves are browning, it may mean insufficient water, especially if the plant is young. Too much fertilizer and sun exposure can also damage the foliage.

More often, though, brown spots on the leaves are due to bacterial blight. This infection typically occurs when growing conditions for the lilac are subpar. The best remedy is to correct the plant's environmental conditions. Also, promptly remove infected foliage to prevent the disease from spreading.