Bean plants are unusual compared to other plants because their seeds develop within a pod rather than a fruit. There are a wide variety of beans for the gardener to choose from. However, all varieties go through the same stages of growth. It's useful to know this process so you know the proper time to harvest your plant whether you prefer to do so when they are bean sprouts or when full-grown pods have developed.
The first stage of the bean plant begins when the seed is planted in soil or soaked in water. The shell of the seed swells before bursting open to reveal a seedling. Two leaves will be visible, which are not yet the true leaves. In this stage the bean plant forms its first true set of leaves, and then two more sets after that. Once the seed is germinated in this stage the plant can be eaten as spouts.
The fourth set of leaves, once the true leaves appear, marks the second stage of the bean plant. The bean plant begins to form branches. Foliage rapidly begins to appear over the plant and the new branches . During this rapid growth the plant is no longer suitable for being eaten as sprouts.
The third stage begins by the first flower opening on each plant. Soon after the first flower opens, half the flowers on each plant begin to open. Next, bean pods begin to develop. The first pod will reach its maximum length. The third phase ends with half the bean pods reaching their full length; however, the beans are not yet matured.
The stage when bean pods reach their full maturity is the fourth stage. Bean pods are ready to be harvested at the end of this stage. It is also the stage where the seeds within the pod are viable. It begins with one pod on each plant becoming fully developed and plump. Next, half of the pod seeds have fully developed. The first pod will change from green to the color that differentiates the bean species from others. This color may be speckled, red, purple or a wide variety of colors and patterns. Once the first bean reaches its color, the others will also begin to reach color maturity until 80 percent of the pods are ready for harvest.