 Can't take up iron, and hydrangea is one of the most susceptible to that. So give it an application of iron. Or Miracle-Gro, the Miracle-Gro company, has a Miracle-Gro for acid-loving plants, and that has a little bit of iron, extra iron in it. So look at the garden center for Miracle-Gro for acid-loving plants and apply that to the hydrangeas or anything else that's looking yellow. Very common this spring and summer.