What Could Be The Cause Of The Discoloration On My Spirea Shrubs?

Question

I have several mature spirea shrubs that form a hedge around my patio. Most of them look healthy, but a few at the end of the hedge have turned pale green this summer with orange discoloration and dark red/purple spots. I had a tree and shrub specialist out to look at it, and he doesn’t know what it is. I also looked up common problems with spirea and none of the issues described seem to match what’s going on here. I included photos of the affected shrubs and the healthy ones right next to them.

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Answer 1

This one is tricky...

I would check the pH and nutrient content of that specific area around that shrub. I see this, sometimes, where a plant is a little more hungry than the rest in an area. This can cause deficiencies in one spot, or pH imbalances.

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm

Otherwise, here are some articles that will offer care tips and more information on the shrub:

https://www.gardeningknowhow.com/ornamental/shrubs/spirea