Deer generally avoid ferns completely so those should be safe. They also dislike ornamental grasses so something like hakone/Japanese forest grass or a Japanese wood sedge (Carex morrowii) would work well also.

Lambs ear. (Stachys)

Near my Bleeding Hearts I have Hellebores and evergreen ferns. But I don't have deer.

Hellebores, they won’t touch them, they ate most of my Hostas this year, they never eat the Ferns or Hellebores.

Kirengeshoma would also make a lovely companion. One deer nibbled on it once about 15 years ago and never since. Totally agree on Hellebores & ferns and I live in the middle of a forest with a massive deer population.

If you were willing to use a spray such as Liquid Fence you could grow whatever you wanted there. I grow a great number of Hostas.

I also suggest hellebore, which is happy in full sun as well as shade --- a really tough but attractive plant.

Do deer eat perennial geranium?

Someone on another thread suggested that I plant geranium macrorrhizum for a shady, somewhat dry area, and I absolutely love it. The deer will walk through it to get to my hosta, but won’t even nibble the geranium. It does spread a lot, but it has pretty flowers for weeks and really worked for my site.

I wish I could say the same for my Johnson Blue geranium. I’m not sure if it’s deer or rabbits, but I’ve given up trying to keep those going. Something eats them down to the ground at the first sign of a flower.

Astilbe have done well in my garden. I sprayed the hosta and daylilies this year and had no deer damage but the rabbits are eating my Liatris.

Deer won't eat G. macrorrhizum or G. 'Biovoko' or 'Karmina', but they will eat with relish all other geraniums.

Deer favor the flowers on my 'Rosanne'....they leave the rest of the plant alone. And they have ignored the other hardy geraniums in my garden. YMMV

Interesting about the geranium and deer. It is like tulips - they are ravenous for all the hybrids but leave the species alone.

Saypoint, if you can get just a bit of dirty cat litter and lightly sprinkle it around your liatris, the rabbits will stay away. It doesn't take much (used as in urine, not poo).

I've recently discovered pulmonaria (lungwort) as an alternative to hosta and our rampant neighborhood deer don't touch them. The silver and spotted leaved varieties are attractive, compact, and should fill in the space when you cut back the bleeding heart. Also love ligularia for shady spots, deer don't bother mine and one would fill in your whole empty space but they might get too big too fast. Here's a Britt Marie Crawford from last summer, also have Bottle Rocket and another variety I can't recall.