Beans grow with little maintenance and produce an abundance of pods. They can add nitrogen to the soil, making them ideal plants for organic vegetable gardens. The plants are easily cultivated but are susceptible to several diseases, such as rust, blight, and wilt. Generally, beans are warm-season annuals that grow erect (bush types) or as vines (pole or running types). The seeds contain a lot of protein and so are often used as a meat substitute. There are many different varieties of bean that have been derived from the original species that come in all kinds of colours and textures.