Christmas cacti are beautiful, low-maintenance houseplants that are perfect for the holidays. To start a Christmas cactus, you'll need to purchase a small plant from a nursery or plant shop. Make sure it has healthy, green leaves and no signs of pests or disease. Then, place the plant in a sunny window or under grow lights. Water the plant regularly, but make sure not to overwater it. Feed the plant a balanced fertilizer once a month, and you'll have a beautiful Christmas cactus in no time.