Q. Since late September my five foot lilac planted on the West side of the house has been showing signs of stress. The lilac made it through the summer fine and all green but has recently shown browning of the leaves despite continuing to bud. I read that fertilizers are not recommended or necessary but I am tempted to try.
A. Both common and Persian lilac grow in our climate. They will not do well in a rock landscape. They prefer soils higher in organic matter. If they are surrounded by rock, they will begin to decline in about 3 to 5 years, leaves will begin to scorch, you may see some branch die back, leaf drop and a reduction or no flowering at all.
Some varieties of lilac perform better here than others such as the early bloomers. An old reliable common lilac is Lavender Lady hybrid one of the first low chill lilacs produced. This particular variety requires less chilling and blooms well here. Another variety to consider might be Excel which also have a lower chilling requirement and is a very early bloomer. I would proceed with caution on low chill, late bloomers such as Angel White, California Rose and Esther Staley unless someone has had a proven record of good blooms and color.
This could be a location problem. A Western exposure is too hot for it. It likes sunlight but not combined with intense heat. It is best to have it in a location protected from late afternoon sun.
But I totally disagree that lilac doesn't require fertilizer. It not only requires fertilizer once a year applied after blooming but, under desert conditions, benefits from compost or organic amendments added to the soil. Lilac will perform well with some unamended arid soils but our desert soils in Las Vegas are just too low in organic matter. Lilac likes a richer soil than unamended desert soils can provide. It likes compost, wood chips as a surface mulch and fertilizer.