The common green bean, scientifically known as Phaseolus vulgaris, is a widely cultivated plant recognized for its edible, immature seed pods. Understanding the plant’s appearance involves observing its unique structure at various stages, from its overarching growth pattern to the fine details of its leaves and reproductive parts.
Two Main Growth Habits
The overall appearance of a green bean plant is defined by one of two primary growth habits, which dictate its size and structural needs.
Bush Beans
The first type, known as bush beans, exhibits determinate growth, meaning the plant grows to a maximum height and then ceases vertical expansion. These plants form a compact, self-supporting mound, typically reaching a height of only two to three feet. This dense structure allows them to produce their entire crop over a short, concentrated period, often requiring no external support structure.
Pole Beans
The second type, pole beans, displays indeterminate growth, characterized by continuous, vining expansion throughout the growing season. These climbing plants can reach heights of 10 to 15 feet, rapidly lengthening their flexible stems. Pole beans require a sturdy support system, such as a trellis or pole, to accommodate their extensive vertical growth. This vining habit allows them to produce beans over a much longer period compared to the bush varieties.
Identifying Leaves and Stems
Regardless of whether the plant is a compact bush or a tall vine, the vegetative parts share a consistent, identifiable structure. The leaves are compound, specifically described as trifoliate, meaning the mature leaf consists of three separate leaflets attached at a single point.
Each of the three leaflets is broadly ovate, or egg-shaped, with the central leaflet often appearing slightly more rhomboidal than the two side leaflets. The leaves vary in color from a light to a darker shade of green, and the surface texture can be smooth or slightly fuzzy depending on the cultivar. They are attached to the main stem on slender stalks.
The stem itself is typically green, sometimes showing a slight reddish hue, and is relatively thin. In pole bean varieties, the stem exhibits a distinct twining behavior, spiraling around any available support as it grows upward.
Flowers and Developing Pods
The reproductive phase of the green bean plant begins with the appearance of small, delicate flowers. These blossoms are bilaterally symmetrical and are often described as pea-like in appearance. Cultivars display a range of colors, most commonly white, but also including shades of purple, yellow, or pink.
Green bean flowers are primarily self-pollinating. Following successful pollination, the flowers quickly give way to the developing pod, which is the edible part of the plant. These pods are technically legumes, forming a boat-shaped structure that encapsulates the small, immature seeds.
The green bean pod typically reaches an optimal length of four to six inches before the seeds inside begin to swell significantly. While most commonly green, the pods can also be yellow (known as wax beans) or purple, depending on the specific variety planted.