Long-living lilac shrubs add color to the home landscape. The emerald green foliage gives way to large clusters of lavender flowers for six weeks each spring or summer. There are both early-bloomers and late-bloomers, so it is possible to plant a few of each and extend the flowering for up to three months. There are also white and pink varieties available. Lilacs are fairly easy to maintain, making them a suitable addition to an informal garden. Gardening lilacs in your landscape brings their low-maintenance beauty to your yard with only minimal effort throughout the year.
Lay a 3 inch layer of organic mulch, such as bark, around the base of each lilac bush. Mulch preserves soil moisture and helps keep the roots cool. Leave a 3 inch gap between the trunk and the mulch.
Water lilacs during extended dry periods in spring and summer. Keep the soil slightly moist but never soggy. Lilacs are drought tolerant and survive some drying out.
Pinch off dead flowers throughout the blooming period to keep lilac at its best appearance. This is known as "deadheading." Dispose of or compost the flowers.
Prune a lilac immediately after it is done flowering. Cut the plant back to seven or eight main stems of varying ages, and trim off the excess stems at the base of the plant (known as suckers) with sharp clean shears. Trim the top growth as desired to shape the plant and to let sunlight into the interior of the lilac. Trim off any dead or damaged branches.
Fertilize a lilac in the fall if the lilac is failing to grow well or isn't producing new shoots. Fertilize with 1/2 pound of 5-10-10 analysis fertilizer per 25 square feet of planting area.
Check the soil pH every three or four years and adjust with lime or sulfur accordingly. Lilacs prefer a soil pH in the 6.0 to 7.0 range; if the pH is below 6.0 (acid) apply an appropriate amount of sulfur, if it is above 7.0 apply an appropriate amount of lime.
Monitor lilacs for pests and diseases and treat any problems that are identified accordingly.
Oystershell scale looks like tiny oyster shells adhering to branches, twigs and trunk. Underneath the "shell" is a small sucking insect. The best time to spray them is when the scales are in their crawler stage and their shells don't fully cover them. During the summer months, multiple applications of horticultural oil and other pesticides may be effective, but heavily affected branches may have to be pruned off.
Lilac borers are moths that tunnel into stems and can cause their death. Look for entry holes. If a stem is lightly infested stick a flexible wire into the tunnels to kill the nesting moths. Prune off more heavily infested stems. After pruning, spray with a lilac borer pesticide and with a fungicide to protect against fungal disease developing in the wounds.
Less harmful is powdery mildew, which appears as a dusty-white color on the leaves in late summer. It's not pretty but is rarely harmful. Potassium bicarbonate spray is effective in preventing mildew.
Leaf miners are tiny insect larvae that feed on the tissue inside the leaves, leaving blotch-like markings. Like powdery mildew, they are largely a cosmetic problem. Sprays and other insecticides are of limited effectiveness against leafminers; the usual treatment is to pinch off affected leaves.