Or, Why Are My Azalea Leaves Turning Yellow?

Most of the subjects of the Great Azalea Migration have settled in well. I pruned them directly after this year’s flowering to give them more shape. Waiting too long to prune risks cutting off next year’s flowers.

This one, however, is showing signs of displeasure.

Notice how the leaves are more yellow than green, but the veins remain dark green? This is a sign of chlorosis, a condition in which the leaves don’t produce adequate chlorophyll. The source of the problem lies in the soil’s pH; if the pH is not appropriate for the plant, that is, if the pH is too low (acid) or too high (alkaline), the plant’s roots cannot take up the nutrients (in this case, iron) in the soil. The solution to such a problem, therefore, is not to dump fertilizer on the plant, but to test the soil’s pH to confirm the diagnosis and then adjust it accordingly.

Azalea Growing Conditions

Azaleas like acid soil, typically in the pH range of 4.5 to 6. My soil falls within this range naturally. But it is possible that when this shrub was transplanted, some lime got mixed into the compost by accident; or it might have happened when I planted some smaller perennials at its base. Azaleas also want a shady location, or one that receives some morning sun. The light exposure is not the problem here.

This condition is interesting to me, because as you can see the older foliage is perfectly green. I would have thought the problem would be more evenly distributed on the plant.

So I will try to get a soil test for this patch of ground in the coming week or so. And if you are very good, I will show you the results and the remedy.