Also known as mums, orange and yellow varieties of these showy flowers often turn up in foil-wrapped pots on people's front steps around Halloween and Thanksgiving. There are 100 to 200 species of Chrysanthemums, and they generally grow low to the ground, but can turn into shrubs. Gardeners plant mums to keep rabbits away. Guess what? The flower heads are somewhat toxic to humans too. But not terribly. Touching them can make you itch and puff up a bit, but probably the doctor will just give you something for the inflammation and allergic reaction.