Azalea leaves turning yellow...why only one bush?

I planted azaleas in my backyard a few months ago. I bought 10 of them from WalMart for a few dollars each and planted them.

They’ve all gotten bigger, and I’ve seen new leaves and growth on all of them, but one has turned yellow.

It doesn’t seem to be dying. The leaves aren’t wilted or falling off, but the leaves aren’t the dark green that you’d normally see on an azalea. It also happens to be the biggest one.

I watered the ground around them pretty heavily when I first planted them and then cut back to running the sprinkler every couple of days for 30 minutes. If we get a heavy rain, I don’t run the sprinkler until the ground seems dry. I know you can kill azaleas by over-watering.

Any ideas why this one has turned yellow? It’s about 6 feet away from the next one, which is fine, so I don’t think it’s bad soil.

Perhaps the soil pH is too high in that spot?
Lots of different problems can cause Azalea chlorosis, but soil pH and Iron deficiency are big players. Look around in the links, and see what might apply in your case.

I’m wondering if a dog is using it as a urinal. This would encourage the dog and others to use it again and again.

Running a sprinkler isn’t the most efficient way to get moisture to the roots of a planted shrub. Maybe the sprinkler pattern is partially missing the affected azalea? The only way to know for sure is to dig down around the plant to see if the soil is moist (or too damp).

Maybe the azalea had problems when you bought it (not a far-fetched idea with cheapie shrubs from Wal-Mart). Could be someone at the store forgot to water that one and it was just starting to stress out when you bought it.

Azaleas do like somewhat acidic soil, but it’s unlikely you are seeing the effects of alkalinity in just that one spot (Chlorosis, in which iron takeup is impaired by high pH, generally shows up as yellowish leaves with prominent green veins, and can be alleviated by using special fertilizer formulated for azaleas).

If the leaves aren’t wilting, it isn’t an underwatering problem. More likely too much water - is it close to a downspout, hose leak, anything that may be watering it? Does it have a different soil beneath it than the other shrubs? How did the roots look (especially compared to the other plants) when you planted it?