Marigolds are members of the Tagetes genus, which contains over 50 species of annual and perennial plants. These members of the sunflower family are native to North and South America, but are grown as ornamental flowers in areas all over the world. Many species have a pungent, musky smell, and are grown to deter insects and nematodes from attacking other flowers and garden vegetables. Marigolds also offer some resistance to deer, rabbits and other animals.
Marigolds vary in appearance from one cultivar to another, producing plants as small as 6 inches high, or as large as 3 feet. These plants produce yellow or orange flowers in most cases, but some specialty types may grow red, mahogany-brown, bicolor, cream or striped flowers. The leaves are fernlike, with a dark green color and strong scent, which can be unpleasant in some cultivars.
According to Rutgers University, the commonly-grown French marigold (Tagetes patula), is seldom seriously damaged by deer. This plant contains chemicals that give it an unpleasant taste, encouraging deer to browse elsewhere. Deer may initially nibble the plant, but tend to avoid it once they realize that it is unpalatable.
While marigolds are unpleasant to deer, this doesn't fully protect them from damage. Deer will test out plants they're not yet familiar with. According to the Michigan State University Museum, these animals may even bite off the flowers, then drop them to the ground once they discover the unpleasant taste. When other, more palatable food is not available, however, deer will turn to browsing on less pleasant plants, including marigolds. To fully deter deer, homeowners may need to fence off the yard or use lights and water to frighten them away.
Not all plants called marigolds are actually members of the Tagetes genus. Another common ornamental plant, called the pot marigold, is actually part of the Calendula genus. This tall, daisy-like plant is even more resistant to deer than Tagetes marigolds, and may be an appropriate choice for environments where conventional marigold cultivars don't repel deer. The plants tend to be somewhat larger than Tagetes marigolds, but produce flowers in a similar range of colors.