According to the University of Vermont, sunflowers are generally resistant to deer, although in early spring, a deer eats most green plants not yet in bloom. Plants rich in protein are the most attractive to deer, and well-fertilized gardens in the early spring and summer are bountiful targets.
Deer derive about one-third of their hydration from plants, especially those with new growth and tender parts. Toxic plants such as daffodil, foxglove and certain mushrooms are instinctively avoided by deer. Plants with strong aromas also discourage deer due to the animal's delicate sense of smell. Deer retain memory of which plants they did not like.