Q: We have 30 dwarf yaupons in our front and back gardens and 7 of them have turned yellow. They have been in the ground for about 10 years and the roots may be affected by our caliche limestone based soil. What treatments can be done and when?
A: First let me warn you that even with treatment, the hollies may never completely green up. Once the roots begin growing into the limestone it is very difficult to get enough product into the soil to do any good. It can be like trying to dilute the salty water of the sea with a few buckets of fresh water. My recommendation is to use a good slow acting high nitrogen based fertilizer at least twice a year and supplement with a granulated Iron product. A Chelated Iron product that can be mixed with water and sprayed on the plants periodically may help to green them up some, but most likely they will remain partially yellow or will gradually go back to yellow over time and the treatments will need to be repeated. This can be a few weeks to a few months or longer. Iron products will stain cement, concrete, brick, tile, light colored stone and terracotta very easily and most times permanently.