I live in zone 14. I have a lilac that has a lot of sentimental value to me, but I can't seem to make it healthy. I'm thinking that I'm either over-watering or under-watering, but I don't know which. Here is what I see:
I'm getting satisfactory growth in height (it's now about 6 ft high now), but the leaves are curling inward, getting brittle, losing their green color, and getting some brownish spots. Leaves near the ground on the younger branches are doing fairly well. Some of the canes were so badly damaged last year that they did not leaf out this year. The lilac bloomed for the first time this spring, but I only got two flowers, and they didn't last long
Last year, my symptoms were similar. I concluded that I was under-watering. I was giving it a little over 2 gallons per week, and I increased the dose to 3 gallons per week. Now I increased it again to about 4 gallons per week -- watering twice a week. There is some moisture in the soil, but it is definitely not wet.
I give it Master Start fertilizer, and sometimes 0-10-10 instead. I fertilize every 6 weeks.
Some of the lilac gets sun all day, and some of it very little. The average is probably about 6 hours of sun per day. I can't be sure whether or not the damage is related to which sections get more sun. However, I can say that last year's damage seemed to occur mostly in the shady areas. This year's damage is higher up and more in the sunlight.
Please help me if you can. My grandmother always had a lilac, and I keep in remembrance of her.