Adding Lilac to the Landscape

Common lilac bushes are deciduous shrubs that bloom in the springtime. They are part of the olive family, along with other such ornamental plants as ash trees, forsythia bushes and privet hedges. The outstanding quality of many lilac varieties is the sweet fragrances of their flowers. The blooms appear 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 – 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 – 2 feet per year.

Care
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.

Light
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.

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.

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 & Humidity
Lilac 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.

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 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. 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. Also, prune any weak or damaged branches.

Common Pests & Plant Diseases
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 fungal 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.

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

Poor Flowering
A lilac that isn’t flowering as much as it used to might need a rejuvenation pruning. To do so, remove a third of the oldest branches right after the bloom period is over. In the next growing season, remove half of the remaining old branches after flowering. And in the next year, remove the rest of the remaining old branches. New branches that flower more vigorously will replace them in a few years.

Leaves Turning Brown
Lilac leaves turning brown might be due to several factors. Insufficient water, especially for young plants, can result in browning leaves. Too much fertilizer also can damage the foliage, as can prolonged exposure to very strong sunlight. Most often, though, brown spots on the leaves are due to bacterial blight. This infection typically occurs when growing conditions for the lilac are subpar. So correcting its conditions is one of the best remedies for the disease. Also, promptly remove infected foliage to prevent the disease from spreading.