deer generally avoid ornamental grasses, salvia, sedums, hardy ferns, heuchera.
There are many. All you have to do is google "deer resistant plants" and you will find lists of them, and forums with people discussing what the deer have or have not eaten in their gardens. Then you have to pick, from those lists, the plants that are suitable for your location. I could tell you what's deer resistant in my garden, but I live in coastal British Columbia which is about as different in climate from South Dakota as you can get. What works here may not work there.
Also keep in mind that while there are plants that deer never eat, there are many more that they will eat only sometimes. Unfortunately, the sometimes often include when the plant is very young and when it's about to bloom, when they eat the flower heads. They may also eat things in late fall or winter that they left alone all summer. They can eat something at your house but not at your neighbour's five miles down the road. Young deer sometimes eat anything, not knowing any better or simply because they are experimenting.
Perennials that are deer-resistant include: hellebore (an early bloomer that has pretty leaves and can come in a wide range of colors), dicentra (bleeding heart), achillea (yarrow), baptisia, foxglove, catmint, blanket flower (gallardia), beebalm, lavendar, peonies, and poppies, echinacea, dianthus or ironweed.
Supposedly they don't eat black-eyed susans, or don't prefer them enough to do serious damage but apparently the deer in my area did not get that memo, so I can't recommend it.
I want to plant flowers but have deer. Which ones will they leave alone? I live in South Dakota
