What's wrong with my dahlia?
I picked up some small dahlias from OSH a few months ago. They were in 6" pots and about 8" tall. I potted them up and put them on my front porch steps. For quite awhile all three bloomed like crazy.
Within the last 3 days, one has started to wilt and shrivel up. The leaves first turned lighter green (but not from powdery mildew or anything) and now are yellowing. There are no bugs on it and I see no cause for the rapid dying. The others from the same purchase look fine, as do my Dinner plate Dahlias that are in the garden beds. My dahlias usually bloom through October then die for the winter, so this one seems to be going abnormally early.
The dahlia is in high quality potting mix and has good drainage. I keep it well watered (but never soggy). It gets about 6 hours of sun each day.
Does anyone have an idea as to why this plant is randomly dying? I moved it away from my others, just in case. I save the tubers each year and re-plant them in the ground. If this one dies, is it worth saving the tuber? Is it likely to be diseased?
Any advice would be appreciated, I really would like to save this plant.