I wish I had read this before purchasing my impatiens. I’ve always had success with them and as one side of our house is totally shade, bought 6 trays of them and planted them.
Of course I lost them all to downy mildew. Why were they being sold with no suggestion that there may be a problem? Lots of time and money gone. Now trying to find things to fill in all the spaces.
It is definitely frustrating when you lose plants to a disease. However, the nursery that you bought the plants from are not necessarily to blame. The fungus Downy Mildew does seem to be more prevalent on impatiens than it use to be but it will only be activated with the right weather conditions. Your impatiens may have not shown any signs of having the disease when you bought them but with all the rain we have had followed by warm nights, it can flourish and damage plants. Apparently the Downy Mildew that attacks impatiens – Plasmopara obducens, does not destroy the New Guinea impatiens so you might be able to substitute with them. A few more part shade ideas would be: Begonia, Coleus, Browallia, Fuchsias, Lobelia, Torenia and Perilla. Begonias and Coleus can handle more shade than the other plants mentioned. Hope it is quick and easy for you to plant more annuals.