I have planted up my hanging baskets and kept them in an unheated greenhouse until the end of May. Unfortunately, every single trailing lobelia plant wilts and dies within four or five days. I have taken out the dead plants and replaced with new healthy ones and once again they have all died! I have made up hanging baskets for the past 30 years and never had this happen before. . . . please help
Are you using fresh soil? It sounds like there may be a bacteria or fungus in the soil that is killing them.
I would discard the soil or sterilize it and wash the containers with bleach before replanting.