Why is it important to rotate crops in the vegetable garden?

Many disease organisms are soil-borne and may persist in the soil for several years.  Disease problems often increase when the same crop is planted in the same area in successive years.  Annually rotating your vegetables in the garden can help reduce the severity of diseases.  Rotation may also help curb insect infestations.  Insect populations and plant damage may increase when the same crop is planted in the same area over several years. 

Vegetable crops in the same botanical family are often susceptible to the same diseases and insects.  For crop rotation to be effective, gardeners should not plant vegetables belonging to the same plant family in the same location for two or three years.  Crop rotation in a small garden is difficult.  However, home gardeners should rotate their vegetable crops as best they can. 

To assist crop rotation efforts, the following list places the commonly grown vegetables in their proper botanical families.  Onions and garlic are members of the Alliaceae or Onion Family.  The Apiaceae or Carrot Family includes carrots and parsnips.  Cabbage, broccoli, cauliflower, Brussel sprouts, kale, and collards are members of the Brassicaceae or Mustard Family.  The Cucurbitaceae or Gourd Family includes cucumber, muskmelon, watermelon, squash, pumpkin, and gourd.  Garden peas and snap beans are in the Fabaceae or Pea Family.  Members of the Solanaceae or Nightshade Family include tomato, pepper, eggplant, and potato.