Beans develop entirely above the soil on a plant, unlike root vegetables. A bean is botanically a seed housed inside a pod, which is the fruit of the plant. The common bean (Phaseolus vulgaris) is a member of the legume family. This growth pattern is distinct from crops such as carrots, potatoes, or radishes, where the main edible portion matures underground.
The Above-Ground Growth Habit
The bean plant develops a root system beneath the surface primarily for stability and to absorb water and nutrients, including nitrogen fixed from the atmosphere. This underground structure anchors the plant, allowing the stem and foliage to grow upward. All reproductive parts, including the flowers and resulting pods, are produced on the aerial portion of the plant.
The edible bean pod forms from a fertilized flower attached to the stem by a short stalk. These pods hang suspended in the air or rest on the leaves, depending on the variety’s growth habit. This placement keeps the developing pods clean, minimizes exposure to soil-borne pathogens, and ensures the seed is protected. The plant uses sunlight captured by its leaves to create the energy necessary to fill the pods.
Understanding Bush and Pole Varieties
The distinction in how beans grow above ground is categorized into two major forms: bush and pole varieties. Bush beans have a compact, self-supporting growth habit, typically reaching a height of only one to two feet. Their sturdy stems bear the weight of the developing pods, so they do not require external structures for support.
Pole beans are vining varieties that exhibit indeterminate growth, meaning they continue to produce fruit until frost. These plants can reach heights between six and fifteen feet, necessitating a trellis or other support structure to climb. The choice between them often depends on the gardener’s need for either a quick, concentrated harvest from bush types or a long, continuous harvest from pole types.
From Flower to Edible Bean
The life cycle that results in an edible bean begins with the appearance of a flower, typically 55 to 65 days after planting. Most bean flowers are self-pollinating. Once the flower is successfully fertilized, the petals drop away, and the ovary swells to form the protective pod.
The timing of the harvest determines the final product, primarily differentiating between “snap beans” and “dry beans.” Snap beans, also called green beans, are harvested when the pod is still tender and immature, often before the seeds inside have fully developed. These are consumed pod and all.
Dry beans, such as kidney or navy beans, are left on the plant much longer, sometimes for an additional four to six weeks, until the pods turn yellow, dry out, and become brittle. This extended maturation allows the seeds inside to fully harden and dry, making them suitable for long-term storage and cooking after shelling.