As the weather begins to turn cold, there are many ways to propagate and prepare your perennials for the following spring. Perennials can be separated and transplanted into pots to be placed on window sills or in a greenhouse. Leaving some of the perennials outside will provide a source of food for animals during the winter. Meanwhile, you can start fertilizing the plants that have been brought inside with sources of nitrogen and phosphorous. These supplements will help them develop strong root systems for the spring and provide more production when the warmer weather arrives.