I live in Wisconsin... I have 4 pots of Lilies of the Nile.....?

Check with your local nursery for recommendations. They know what works in your area.

• For lots of beautiful flowers, choose a hydrangea that’s cold hardy in your garden zone. Check the plant tag to see if it requires sun or shade, so you can plant it in the right spot. Early summer and fall are the best times to plant.
• Put your hydrangea where you won’t have to prune it. These shrubs grow vigorously, and besides—they’re big and beautiful by nature.
• Plant in soil that drains easily, and add good organic material, if needed, to help loosen it.
• Don’t plant your hydrangea any deeper than it was growing in the pot.
• Avoid planting under trees, where the roots will compete for moisture and nutrients.
• Keep your hydrangea watered for the first couple of years, to help develop strong roots. But don’t let water stand around your plants. Oakleafs are especially prone to root rot when they are kept too wet.
• Fertilize once a year with a balanced, slow-release fertilizer, or fertilize twice a year with 10-10-10. Commercial manure or compost is an organic alternative. Stop fertilizing by August to let your hydrangea get ready to go dormant.

Cut hydrangeas back in the fall. Here are some tips https://www.hometalk.com/diy/grow/flowers/hydrangea-grow-prune-dry-decorate-4524029

Best Hydrangea Tips, a Full Guide! How to Grow, Prune, Dry, Display +

Also, as far as the lily of the nile, there are different types which require different care but all the details can be found at https://wimastergardener.org/article/agapanthus/