Yellow patches on many perennial garden species
This spring I noticed yellow spots/patches on many of my perennials in one of my gardens. Most of the plants have been in this garden, which surrounds a very large brick patio for 2-3 years. My soil is *very* sandy and I do not amend or fertilize (I want low maintenance gardens, if it doesn't do well, I'll try something different). We did put down about an inch of uncolored mulch last spring, but it wasn't enough and we'll be adding more this year. I noticed the yellowing first on a grape vine. Some of the grape leaves are like the picture, some are more patchy. I then realized that many of my other plants showed similar symptoms: anise hyssop (pictured), penstamon (pictured), phlox, wild violets, salvia, hydrangea, and more. Other than the discoloration, the plants look great and are all growing well. I'm most concerned if this is some sort of widespread infection, though I was also wondering about chlorosis (but why didn't it happen in the past or elsewhere in my yard?). Thank you so much!!!
Anoka County Minnesota