Deer are ruminants, which are hoofed animals that chew cud. There are over 40 species and over 100 types of deer, with different sizes and markings, prevalent around the world. Deer are native to Asia, Europe, Africa and South and North America. They have a strong sense of smell that protects them from their enemies by alerting them even when their predators are far away. Deer like to eat trees including apple and cherry, as well as plants such as clematis, hemlock, yew and much more. There are a few types of vegetable plants that deer do not eat.
Garlic, also called Allium, is one of the vegetable plants that deer do not eat, perhaps because of its strong odor. Garlic is used as an ingredient in strong deer repellent agents such as Liquid Fence spray. Garlic oil is also effective in manufacturing garlic oil repellents that keep away deer.
Onions, which are in the same family as garlic and have a pungent smell, are used as deer-repellent plants. Because deer are very sensitive to scents and depend heavily on their sense of smell, they dislike onions. Onion plants can also be used as bordering plants instead of fences normally used for deterring deer around gardens.
Another kind of vegetable plant that deer do not eat is rhubarb. Rhubarb is in the family Polygonaceae and has huge, toxic leaves that deter deer from approaching them. Only its stems can be consumed while its leaves contain oxalic acid that is poisonous to humans. It's a perennial plant with a disagreeable smell. Rhubarb is hardy in both extreme cold and dry climates. One can grow and even neglect rhubarb because it's a very enduring and frost-resistant plant.