Black walnut trees produce a natural chemical called juglone, which is released into the soil through their roots, leaves, and fallen debris. Juglone can be toxic to many plants.
Deer will eat anything if they are hungry. The best approach is to use plant material that isn't appealing to consume. Typically plants with spiny or fuzzy foliage, a strong scent, and those known to have toxic properties aren't appealing.
Due to its gritty nature, sandy soil allows for good drainage and healthy root development. Some plants, however, may struggle to cope with its tendency to become parched and its relative lack nutrients.
With a little attention early on—watering, mulching, and monitoring for pests or stress—your plants will thrive and reward you with years of growth, blooms, and natural beauty.