Our gardens may be blanketed in snow, but winter is the perfect time to dream about spring blooming lilacs. The National Garden Bureau (ngb.org) has declared 2022 the Year of the Lilac and offers the following helpful information. I’ve tailored the information for our southern Ontario gardens.
Lilacs are spring-flowering, multi-stemmed, deciduous shrubs (or small trees), well-loved for their toughness, reliability, and delicious fragrance.
Overview and history
Clusters of small, four-lobed flowers are borne in conical to narrow pyramidal clusters (panicles) up to 20 centimeters long that stand out from the green heart-shaped leaves.
Carl Linnaeus first described the lilac genus, Syringain 1753. The name is derived from the ancient Greek word syrinx, meaning pipe or tube. The stems of the common lilac have a sponge pith that can be removed, leaving hollow tubes that were used to make pan-pipes.
Syringa vulgaristhe common (vulgar) lilac, originating in southeastern Europe; other species came from Western Asia. The French imported lilacs and developed many new varieties that made their way to North America. There are about 30 species of lilac, including: Chinese, Hungarian, Cutleaf, Korean, Persian, Preston (Canadian), Japanese tree and common.
Lilac blooms appear in every imaginable shade of lilac / purple from very pale to very dark. Look for lilacs in hues of red, pink, blue, yellow, cream and white – even picotee (white-edged, deep purple ‘Sensation’). The color may change from bud to bloom and as the flowers mature. Individual flowers can be single or double.
Did you know?
Lilacs can grow for 100-plus years, often outliving the homes they were planted around. New lilacs are being bred for an extended bloom time or re-bloom, a more manageable stature and more heat tolerance. Purple lilacs represent love and spirituality; they traditionally have the strongest scent. White lilacs symbolize purity and innocence.
Lilacs in the garden
Lilacs are very adaptable to modern gardens. A range of sizes and re-blooming characteristics make them attractive and accessible to gardeners who may not have thought about growing them in the past. Smaller lilacs work well in container gardens. At home in many types of themed gardens, include them in pollinator, butterfly, cutting, fragrance, cottage, deer-resistant and single-color (white, purple) gardens.
Lilacs are great in mass plantings such as a flowering hedge, border, windbreak, foundation planting or privacy or screening hedge. Lilacs of any size can be impressive specimen plants. These versatile shrubs are equally comfortable at the edge of a woodland garden or in an urban setting. In containers, small varieties are moveable accent plants. Lilac colors blend so well together, they are beautiful in a grouping or hedge of many different cultivars.
Lilac planting tips
Now lilacs do well in hardiness zones 3 to 7 – climates that provide a chill period in winter. They are well suited to the gardens of southern Ontario. Lilacs grow best in full sun, so avoid planting them where they will be shaded for more than a few hours each day. They also prefer good drainage and fertile soil. Soil should retain sufficient moisture to nourish the root system yet drain freely when rainfall is abundant.
Tip: If you are not sure about your soils drainage, try this test. Dig a hole 20 centimeters across and 30 cm deep, fill it with water. If any water remains in the hole after an hour, choose another planting area.
Lilacs love fertile, slightly alkaline soil. If your soil is very acidic, add garden lime in the fall. Check the plant label for the height and spread of the mature plant, and choose a planting space that will allow for growth. Dig the planting hole as deep as the root ball and twice as wide, set the plant in the hole; it should be at the same soil level as it was in its container.
Fill in around the sides with soil. Press it firmly and water well.
Lilac growing tips
Water your lilacs regularly for the first couple of years – at least 2.5 cm of water a week. Apply granular organic fertilizer early each spring at the base of the plant. Water it in well. Buds are set the previous year, so the fertilizer feeds this year’s leaves and next year’s blooms.
Annual pruning is not necessary, but cutting off spent flower heads within a month after bloom helps the plant set more flowers for next year. Prune out any dead or broken branches from storm or winter damage, as required. Cut off root suckers as they appear to keep the common lilac from spreading into a colony.
To rejuvenate an overgrown plant, or one that blooms sparsely, cut it back over a three-year period. In March or early April, remove one-third of the large, old stems at ground level. The following year, prune out one half of the remaining old stems. In the third year, remove all of the remaining old growth. Thin some of the new shoots each year, retaining several well-spaced vigorous stems. Lilacs bloom on wood that is at least three years old. This will refresh the plant without sacrificing blooms.
Powdery mildew can be unsightly, but generally does not harm the plant. You can make a spray of two tablespoons of baking soda in a gallon of water with a couple of drops of Ivory dish soap. Spray it on the leaves, but not if the temperature is above 27 C. The alkalinity of the solution helps to kill the fungus.
Rake fallen leaves from around the plant in autumn. If you had powdery mildew or any disease, bag them and toss them in the garbage; unaffected leaves can be added to your compost pile.
Prune out any dead or broken branches from storm or winter damage.