The Q&A Archives: Lilac Leaves Yellowing

Question: I live in Zone 23. I bought a Syringa Vulgaris "Lavender Lady" last January. The tree is young, being only about 18 - 22" tall. I've planted it on the South side of my yard and it gets full sun. The lilac tree's leaves yellow and fall off and has done so several times. New buds and green leaves have grown once but after a month or so turn yellow and fall off. I've fertilized it with azalea fertilizer (acidic) several times. What can I do to have a healthy tree that produces fragrant blooms?

Answer: The common lilac (Syringa vulgaris) will grow in your area, but may not bloom faithfully for you. Lilacs need a pronounced period of cold weather to bloom best, and yours is a mild winter area. You've chosen one of the Descanso Hybrids that have been developed to perform especially well in Southern California, so once your plant is established, it should provide lots of lovely blossoms. Lilacs prefer to grow in full sunshine, in average soil, with regular watering during spring and summer. Once established, lilacs grow lush and full and may need annual pruning to keep them within bounds. Prune after flowering to allow the development of buds for next year's bloom. Lilacs are reliable shrubs in the landscape and can be trained into a tree shape by removing all but one main stem, and keeping the new shoots rubbed out before they become branches.

Yellowing leaves might indicate the plant isn't getting the moisture it requires. Water deeply once a week during the growing season, and add an organic mulch over the root area to help slow down moisture evaporation. Lilacs prefer an alkaline soil, so instead of using an acid based food, try fertilizing with a 5-10-10 general purpose garden fertilizer.

Hope your lilac perks up this season!

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