It is cercospora and very common on oakleafs, especially when grouped tightly together like at the nursery. Not harmful, just unattractive. Good air circulation and an occassional spray of Immunnox minimizes the condition. Bayer also makes a systemic product. New leaves will come out clean so prevention is key. If there aren't too many, I pick off the spotted leaves. If the whole plant is covered, might as well wait until next season and try to head it off at the pass. I have one SnowQueen that has almost flawless leaves, an Alice with about 1/8 of the leaves spotted, and three species quercifolia, one in great shape and the other two that came from the nursery this year that are covered with it. The longer the leaves are on the plant, the further it progresses. By Fall when the leaves turn, it will just blend in / be part of the normal color change.

If the plant looks otherwise healthy, don't let the spots deter you from buying it. SnowQueen (my favorite) will make an elegant shrub and I think you will not regret buying it......yg

Thanx, YG! By the way, would an oakleaf or a paniculata (like limelight) cope better with dry conditions? I have read a lot of conflicting opinions!! TIA!

i have both snow queen and limelight. i planted 2 snow queen last fall and only watered when we went through that terrible dry spell in late spring. since we have had the consistent pm thunderstorms, have not had to supplement. it gets morning to early mid-day sun. hard to say which needs more or less, as limelight is in a wetter and shadier location.

And I don't have the red spots on the snow queen leaves either...

Depends....Oakleafs can grow well in quite a bit of shade whereas the Limelights need much more sun to bloom well. Therefore, even though technically Paniculatas are less thirsty than Quercifolias, the Limelight in the sun will require more water than the oakleaf in part shade. Both will need regular watering until established but keep in mind that they are both 'hydra'ngeas and neither should be grown in 'dry' conditions. Even moisture is always best....yg

I had read that those spots on Oakleaf hydrangeas in stores were from overhead watering while they were in greenhouse. I had them as well on a SnowQueen and on Alice. I am hoping they won't be there next year when they get their new leaves.
Mary