Planted a hosta garden around an old maple tree. Put down newspaper over grass, as digging was not an option, then filled with new black soil. All has been well until this week (about a month in) and now have white circles about 8 inches in diameter evenly spaced through garden that looks like frost patches that can be brushed away. Any ideas on what this is and what to do about it?
Newly Planted Hosta Garden
Certified GKH Gardening Expert
This sounds like powdery mildew. Neem oil can help with this. Here is more information: https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm