Q.Holly bushes are turning yellow
Holly bushes are turning yellow from bottom foliage and spreading up, losing leaves and branches dying. Put iron on them and sprayed with general pest/disease treatment. Not sure of cause but has clay in soil and not best drainage but plants have been here two years.
As you have already determined, yellowing leaves on holly bushes can be caused by an iron deficiency. Poor drainage, overwatering and a soil with too high of a pH are the most common causes of iron deficiency.
Clay soil is not well draining so you may want to consider amending the soil to fix the drainage. For tips on how to improve clay soil, please visit the following link:
If your iron treatment does not work, I suggest that you get a soil test done via your local extension office to see if the pH of your soil needs to be adjusted. To find the closest extension office near you, please visit the following link:
For more information on yellowing holly leaves, please visit the following link: