Green beans (Phaseolus vulgaris) are a staple crop found in gardens across the world. Whether these plants climb is not a simple yes or no, as the common green bean exhibits two distinct growth patterns. Some varieties ascend vertical structures, while others remain compact and self-supporting. Understanding these differences is the first step in successful cultivation, influencing the need for support and the timing of the harvest.
The Two Primary Growth Habits
The distinction in growth habit is based on whether a variety is classified as a pole bean or a bush bean. Pole beans are vining plants with an indeterminate growth habit, meaning they continue to grow, flower, and produce pods throughout the season until the first frost. These vines can reach lengths of six to ten feet, making a support structure necessary for their health. Pole beans generally take longer to reach maturity (65 to 80 days), but they offer a higher total yield over the season from a smaller ground footprint.
In contrast, bush beans have a determinate growth habit, terminating growth once the plant reaches a compact, self-supporting height, typically less than two feet. These varieties set the majority of their flowers and pods around the same time, offering a concentrated harvest period usually within 45 to 60 days of planting. This simultaneous production makes them popular for gardeners who prefer to harvest all at once for canning or freezing. Bush beans do not require external support, as their stems are strong enough to hold up the plant’s weight.
How Pole Beans Achieve Vertical Growth
Climbing varieties use a specific biological mechanism known as volubility, or twining, to achieve vertical growth. Unlike peas or grapes, pole beans do not possess specialized grasping organs called tendrils; instead, the entire growing tip of the vine circumnutates, or rotates, in search of a support. When the searching vine makes contact with a vertical structure, it wraps its stem around it, beginning the climb.
This wrapping motion follows a consistent, genetically determined pattern, known as a right-handed helix. When viewed from the top looking down, the vine always twines in a counter-clockwise direction around the support. This inherent spiral growth is not dependent on environmental factors like the sun’s movement or the earth’s rotation, but is rather a built-in feature of the plant’s growth hormones.
Essential Support Structures for Climbing Varieties
Because pole beans are engineered to climb and reach significant heights, providing a sturdy, tall support system is necessary. Support structures must be installed before or immediately after planting, while the seedlings are small, to prevent damaging delicate roots later on. Waiting until the vines are long risks injury to the plant when trying to train the floppy stems onto the structure.
Effective supports should generally be between six and eight feet tall to accommodate the full growth potential of most pole bean varieties. Common structures include simple vertical poles, which gave the beans their name, or A-frames and teepees constructed from bamboo canes or sturdy wooden poles. A-frames are particularly space-efficient for narrow garden beds, while teepees provide a robust, wind-resistant option.
Wire mesh or nylon netting attached to a frame makes an excellent trellis, offering the vines multiple points of contact for their twining stems. Regardless of the design chosen, the framework must be strong enough to bear the substantial weight of a mature, heavily laden vine, especially when exposed to strong winds and rain. Using rough materials, such as untreated wood or natural twine, can provide better grip for the climbing stems than slicker surfaces.