Thorns and briars pose no problems to deer, but the fibrous or fuzzy foliage of ferns, ornamental grasses, tarragon and wormwood (Artemesia), lamb's ears (Stachys) and borage-family plants like bugloss (Anchusa), borage, heliotrope, Virginia bluebells (Mertensia), forget-me-not (Myosotis), and lungwort (Pulmonaria) appear to be difficult for deer to swallow. Because silver and gray leaves are often furry and pungent, these plants are good deer-repellent choices for many gardens.
Unappetizing to a deer means lemony, minty, sagey, spicy, or bitter. Pungent herbs are good garden choices. Peppery flowers of the mustard family including alyssum, Arabis, aubrietia, snow-in-summer (Cerastium), dame's rocket (Hesperis), candytuft (Iberis), nasturtium, pinks, carnation, and sweet William, Lychnis, soapwort (Saponaria) and Silene.
Deer also avoid plants considered medicinal and poisonous: foxgloves (the plant source of the cardiac drug digitalin), poppies (the plant source of opium), daffodils, and lily-of-the-valley. Herbals and are also unappetizing to deer.
Many young plants are lost to deer because fertilizer or ample watering made them temptingly tender. Nitrogen is the basic building-block of protein for deer and one of the big three plant nutrients, along with phosphorus and potassium. Fertilizer makes for numerous green leaves, but at the expense of weak cell walls. Feed the soil, not the plants, to make flowers and shrubs less appealing to hungry deer.
New plants are also vulnerable to deer damage. Besides being coddled at the nursery with fertilizer and water, they face transplant stress. Cove them with floating row covers or temporary cages until they acclimate and reducing fertilizer will often get them safely through a critical period.
Because deer are browsers (brush eaters) rather than grazers (grass eaters), the sight of deer grazing the lawn may be a sign of excess soil nitrogen, either from fertilizer or even from leaking sewage. Amend your gardening and home-maintenance practices accordingly.