This will allow your plants to be able to better withstand pests, drought and other potential problems. The key to improving the soil is to do it before you plant a new perennial bed. If you incorporate the proper amounts of organic matter and soil amendments, your soil will provide nutrients and make air and water more available to plants. This may be hard work, but in the long run the plants will do better. When you choose a site for a perennial bed, it is important to check the water drainage.
Proper drainage is a key factor in winter survival.
Dig a hole 12 inches wide and deep. Fill it with water and let it drain. Fill it with water again. The water should drain in less than an hour. If it doesn't, consider another location or improve the drainage by installing drainage tiles.