I love annual vinca. Once they get established, they are beautiful, carefree plants that love the heat and dryness of our Midsouth summers.
But last year, my annual vinca suffered from a fungal infection that nearly wiped them out. My vinca bed is the hottest and driest area of my garden in the summer, a perfect location for vinca. But it is also low and tends to hold water in the late winter and early spring, creating conditions that promote fungi. I attributed my problems last year with wetness, so this year I added extra garden soil and soil conditioner to the bed to promote better drainage. I also delayed planting until last week, thinking that the hot weather would be just around the corner, and then I only planted a single six-pack as an experiment.
As you can see from this picture, my caution was well-founded. Several plants have died completely and others are nearly dead. I have other plants growing in this area that are not so susceptible to these types of fungi and they are doing fine. A publication from the University of Arkansas recommends that gardeners use these alternative plants once the fungus has been introduced into the bedding area, so I guess I won't be planting vinca here for awhile. Next year, I'll pick a different site and wait even later to plant. And maybe the weather will be more cooperative.