Native to the Balkan Peninsula, lilacs have long been revered for the heady scent of their abundant flower clusters. In the 1500s, the flowering shrub found its way to northern Europe, and settlers brought it to North America in the 1700s. New Hampshire even made the lilac its state flower.
The common lilac (Syringa vulgaris)—also known as the French lilac or simply the lilac—is a member of the olive (Oleaceae) family. Its relatives include ash trees, jasmine shrubs and vines, forsythia bushes, and privets. The common lilac is a popular ornamental landscaping plant that's fairly low-maintenance under the right conditions.
Caring for the Common Lilac
The common lilac prefers USDA growing zones 3 through 7. Plant your lilac in an area that gets at least six hours of full sun each day. The shrub will grow in some shade, but it likely won't produce as many of the prized blooms.
Common lilacs like loamy, somewhat moist, neutral to slightly alkaline soil, and they must have good drainage to avoid root rot and other diseases. They can tolerate the occasional drought but likely would benefit from watering during excessively hot, dry stretches.
Moreover, test the soil before you add any fertilizer. Unless the results show a need for a certain nutrient, you probably won't have to fertilize your lilac for several years. In fact, an excess of nitrogen can harm the plant.
Lilacs readily spread through suckers. If you want to propagate the plant, simply dig around a new shoot and cut it from the main plant, taking care not to damage its roots. Then, replant it in a new location, and keep it well watered until its roots take hold. However, if you don't want your lilac to spread, just trim off any suckers to keep it under control.
Pruning the Common Lilac
Lilacs require good air circulation to deter certain diseases. Pruning can achieve this, as well as help to maintain the shape, size, and general health of the plant. Common lilacs can reach anywhere from 8 to 20 feet tall and 6 to 12 feet wide, depending on which variety you plant. They generally grow in round, oval, and irregular shapes.
These plants typically bloom for three to four weeks in late spring, though this can vary depending on the variety. The ideal time to prune is just after the blooming period is over. Lilacs bloom on the previous year’s growth, so you want to give a plant plenty of time during the season to grow and set buds.
Lilacs fall under the general guideline to prune a third of the shrub each growing season. Take off any dead or diseased wood, as well as the spent flowers. Also, remove stems that are thicker than 2 inches in diameter to prevent the plant from becoming too tall. And prune the remaining stems to create the shape you desire.
Pests and Diseases
Lilacs can fall prey to several pests and diseases, though certain varieties are more hardy than others. Potential threats include:
Common lilac pests:
- Aphids (Aphididae family)
- Citrus nematode (Tylenchulus semipenetrans)
- European fruit lecanium (Parthenolecanium corni)
- Fuller rose beetle (Asynonychus godmani)
- Ground mealybug (Rhizoecus kondonis)
- Lilac borer (Podosesia syringe)
- Mice (Murinae subfamily)
- Oystershell scale (Lepidosaphes ulmi)
- Voles (Arvicolinae subfamily)
Common lilac diseases:
- Armillaria root rot (Armillaria mellea)
- Bacterial blight or canker (Pseudomonas syringae pv. syringae)
- Botryosphaeria spp. (causes fungal dieback)
- Botrytis blight (Botrytis cinerea)
- Gray mold
- Nectria spp. (causes fungal dieback)
- Phomopsis spp. (causes fungal dieback)
- Phytophthora spp. (causes fungal dieback)
- Powdery mildew (especially prevalent in common lilacs)
- Tubercularia spp. (causes fungal dieback)
- Verticillium wilt (Verticillium spp.)
The best defense against these pests and diseases is to provide your lilac with optimal growing conditions. Check your plant regularly for problems, and treat or cut off diseased areas as soon as you spot them.
Landscape Design for the Common Lilac
Lilacs can be a wonderful addition to your landscape. And there are hundreds of lilac varieties available in an array of colors, including:
- 'Andenken an Ludwig Spaeth' (purple)
- 'Belle de Nancy' (double pink)
- 'Krasavitsa Moskvy' (pale pink)
- 'Leon Gambetta' (double purple)
- 'Miss Ellen Willmott' (double white)
- 'Mme. Lemoine' (double white)
- 'Primrose' (yellow)
- 'Wedgwood Blue' (blue)
- 'Wonderblue' (sky blue)
- 'Yankee Doodle' (purple)
Along with specimen plantings, lilacs are commonly used as screens and hedges. Dwarf lilacs, which generally reach around 3 to 4 feet tall, are great for small gardens and can even be grown in containers. Plus, lilacs can attract birds, butterflies, and other pollinators to your garden.
If you plant multiple varieties of lilacs in your garden, consider selecting ones that bloom at different times. This way, you might be able to get six weeks or more of blooms throughout the spring. Many gardeners prefer to plant their lilacs near a window, patio, or pathway where they can enjoy the scent of the fragrant blooms.