When plants are moved East-West they are more likely to do well. North-South is a different story!
https://planthardiness.ars.usda.gov/I wanted to buy Eel Grass & American Pond Weed from a nursey in New England, plants there were already shutting down for the winter because of the cold. Here in Florida we are still in the high 80's. I will have to order & plant in the early spring so that the plants are in & growing before they are stressed with our 95 degree days.
If you bought yours in MI, perhaps a spring or late summer planting to get them established before the limiting stress factor in MI , your cold winters. Plants are bare root, they have lost many of their small & hair roots that they depend on to survive. They are in stress till these are regrown.
For the truly ambitious & green thumb want to be, get used gallon pots from the local landscape guy, fill with dirt & plant your pickerel weed, water once with a growth hormone fertilizer, leave outside in a sheltered area & keep moist with just water, wait till the nights are cold & then keep in the garage till spring but keep moist not wet. Once the plants are growing well plant in the pond. A slow release fertilizer tablet or two in the hole would not hurt at this time.
