Poor Growth and Flowering of Lilac
Our lilac gets very few leaves, and the flowers are very small. The bush is about 11 years old. The people who owned the house before us covered the soil around the bush with rocks. Should we remove the rocks and work up the soil?
Lilacs need full sun and good air circulation for the best growth and flowering. Excess shade can reduce flowering and increase the risk of powdery mildew disease. Move plants to a sunnier location if needed. Transplant in spring before growth begins. Renewal pruning will help encourage new growth and improve flowering. Remove one third of the stems back to ground level. Reduce the height as needed. Prune after bloom to enjoy the flowers and finish pruning by early June to avoid eliminating next season's floral display. Repeat this next spring. At the end of three years you should have healthier and more attractive growth. Remove the stone and weed barrier, if present. Replace the stone mulch with woodchips or other organic mulch. Test your soil before adding any fertilizer. The soil test report will tell you what type and how much fertilizer to add to your soil.