Hi. I am posting a question for my dad who lives in Iowa. I don't know what the acidity level of the soil is there, but that's the part of the US. He is wondering why any kind of yellow perennial is the hardest to keep alive? They keep dieing. It does not matter what kind of perennial it is. If the perennial is yellow, they keep dieing. He has several other perennials and roses and does fine with them all, but anything that is yellow - even roses are harder to grow and keep living. He does have experience as several of his other roses and perennials do really well. He's good at planting. But, it's just something about yellow perennials and he is wondering why or what he can do. He dug up one, and replanted a new flower and it died too. It's not the same location in the yard either. It's just something with yellow perennials. Does anyone know why? Thank you for any help you can give please. My dad is elderly and loves taking care of his flowers and I am trying to help him however I can. This is my first time finding this forum.