Hundreds of varieties of beans exist in the world today. Some produce just one crop per season, while others can produce over and over throughout the season. Some are short, bushy plants while others are climbing vines that need support to keep them off the ground. Some bean plants produce beans that must dry out on the plant before harvest while still others are harvested before the beans can swell inside the pods. In spite of the great variance, most bean plants share a similar structure, with similar components.
Roots are the anchor of the bean plant. One main tap root grows straight down into the soil. In addition to holding the bean plant in place, the tap root also takes in water and nutrients from the soil and provides support for the stem. It also stores food for the plant. From this, multiple hair-like roots branch off horizontally. These assist in absorbing water and nutrients.
Cotyledons are called the seed leaves. They provide a temporary food supply for the plant when it first germinates and begins to sprout. Shaped like the seed, these leaves push out of the seed coat and form the first pair of leaves as the plant emerges. Bean plants are classified as dicots because they have two cotyledons, or seed leaves.
The stem can be compared to the spine in an animal, supporting the entire plant. Depending on the variety of bean plant, the stem can be 12 to 18 inches tall for bush-type beans and 6 feet tall or more for climbing types. The stem carries fluids between the roots and the shoots and stores nutrients. Along the stem are nodes and internodes. The nodes are places where buds, either leaf or flower will erupt. The internodes are simply the space between the nodes.
Leaves are attached to the stem by petioles, a kind of stem for the leaf that is actually the midrib or main vein of the leaf. The leaves purpose is to perform photosynthesis. Part of their function is to absorb carbon dioxide and to transpire or release excess water into the atmosphere. They store food and water.
Flowers begin the reproductive process for the bean plant. The bean plant, depending on the variety, continues producing flowers throughout the growing season. Once the flower is pollinated, the petals begin to fall away and tiny bean sprouts from the node. With some varieties, the more frequently the beans are harvested, the more flowers will be produced. Blue Lake and Kentucky Wonder are examples of beans that continue to produce during harvest.
Beans are actually grown inside pods. Depending on the variety, the pods will elongate. For snap beans, the pods should reach a length of about 4 to 6 inches with a uniform thickness before harvesting. Dry beans are left on the plant until the beans swell within the pods and the skin of the pod dries out and turns brown. Then the pods are picked and the beans removed.