I’m not familiar with your conditions, so can’t recommend plants, but one thing strikes me from the photograph. Are you intending to backfill behind the wall? If so the tree is going to be badly affected, possibly killed, by the root flair and trunk being buried.

Your zone?

Thanks all. No, we are not backfilling behind the wall. The wall and tree have both been there for a very long time...100 years at least. We just rebuilt the wall as it had fallen over. 10a.

My experience has been that 'nobody' eats Salvias, which is why I had a garden full of them when living out in a very rural area with lots of deer. Any herbal kind of plant is usually safe.

Nepatas are usually a good choice too.

The deer ate my anemones...

Lower/smaller growing plants that the deer don't seem to bother in my yard are campanula, hellebore (tolerates southern exposure for me, but might not if you are in a warmer zone), geraniums, catmint, heuchera, japanese painted fern, mini/groundcover roses. Roses and catmint will probably require periodic trimming back; Heuchera might be your best bet.

LOL!! Deer eat my heuchera back to the ground....in the same manner they hoover up hostas! They also graze all my hardy geraniums and nip the flowers of the zonals (Pelargonums).