Question: My Texas mountain laurel has yellow leaves, and they continue to get more yellow as time goes by. It faces southwest, has two adjustable emitters turned down low, watering once a week for one hour in the winter. In early August, I fed it with a fertilizer for acid-loving plants. I have looked very closely for bugs and see none. There are some brown spots that have been appearing on the leaves.
This plant is native to the Chihuahuan Desert and so is accustomed to very low rainfall, particularly during the summer.
This doesn’t mean you should not water it in the summer, but it does tell me that it would prefer deep but less frequent irrigations at that time of the year.
It is also not accustomed to high amounts of fertilizer and does not need fertilizers blended for acid-loving plants.
This plant grows easily in alkaline soils. It is a legume, so go lightly with the fertilizers.
Generally speaking, deep irrigations to a depth of 12 to 18 inches once a week should be fine during the summer months.
You should be able to water less often in the winter.
They are found on rocky soils in the desert, but I am sure they would prefer improved soils as long as they drain water.
In the spring, this plant tends to get a caterpillar, the larva of the Genista moth, that feeds on the leaves.
Sprays containing Bt, such as Dipel, Thuricide or even Spinosad, should control it with one or two applications when you start to see them.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at email@example.com. Visit his blog at xtremehorticulture.blogspot.com.