Culture Notes
Hungarian Lilac is a late flowering shrub that grows best in a sunny location. The plant will grow in shade but flowering is poor and powdery mildew is likely to be severe. The growth rate is rapid and the plant produces many suckers. The flowers are in shades of purple, white or pink, with few actual color variations. Some colors listed in catalogs refer to the unopened flower buds and the flower color itself may be different. Pollen bothers certain people. Pruning should be completed after flowering and by late spring to ensure next year's flower buds are not removed.
Planting and establishing shrubs
The most common cause of young plant failure is planting too deep. Plant the root ball no deeper than it was in the nursery. In most instances, the root flare zone (point where the top-most root in the root ball originates from the trunk) should be located just above the landscape soil surface. Sometimes plants come from the nursery with soil over the root flare. If there is soil over this area, scrape it off. The planting hole should be at least twice the width of the root ball, preferably wider. In all but exceptional circumstances where the soil is very poor, there is no need to incorporate anything into the backfill soil except the loosened soil that came out of the planting hole. Never place ANY soil over the root ball. If a row or grouping of plants is to be installed, excavating or loosening the soil in the entire bed and incorporating organic matter enhances root growth and establishment rate.
Weed suppression during establishment is essential. Apply a 3-inch thick layer of mulch around the plant to help control weed growth. Keep it at least 10 inches from the trunk. If you apply it over the root ball, apply only a one or two inch layer.  This allows rainwater and air to easily enter the root ball and keeps the trunk dry. Placing mulch against the trunk or applying too thick a layer above the root ball can kill the plant by oxygen starvation, death of bark, stem and root diseases, prevention of hardening off for winter, vole and other rodent damage to the trunk, keeping soil too wet, or repelling water. Regular irrigation through the first growing season after planting encourages rapid root growth, which is essential for quick plant establishment.Â
Pests, Diseases and Damaging Agents
Pests: If properly located on an appropriate site, there are few problems. Lilac borer larvae tunnel in the branches, causing wilting, particularly on drought-stressed trees. Lilac leaf miner tunnels in the leaves in early summer. Scales are most often found infesting the lower stems and often blend in with the bark.
Diseases: Usually free of serious disease. Bacterial blight is most serious on white flowered selections. Phytophthora blight kills stems to the ground. Leaf blotch causes zoned, brown spots. Many fungi cause leaf spots. Powdery mildew coats the leaves with white powder. Verticillium wilt causes wilting and premature leaf drop. The disease may kill one, several or all the branches. Try fertilizing regularly to help prevent diseases. Bacterial crown gall causes round, warty galls on the stems near the soil line.