Most pea plants (Pisum sativum) are climbers, often referred to as vines in gardening, though this is not a strict botanical term. The pea plant’s growth habit is to ascend, seeking light and support. This climbing characteristic gives the species an appearance similar to true vines. Without external support, the stems of most pea varieties are too weak to stand upright on their own.
The Climbing Mechanism of Pea Plants
The specialized botanical structures allowing the pea plant to climb are called tendrils. These thin, thread-like organs evolved from modified leaves or stipules. Tendrils emerge from the plant’s nodes and actively explore the surrounding air for an object to grasp. Their searching motion is a slow, helical movement called circumnutation, which helps them detect potential support.
Once a tendril brushes against a narrow support, it triggers positive thigmotropism, which is directional growth in response to touch. This reaction causes cells on the side of the tendril not touching the support to elongate more quickly. This differential growth causes the tendril to rapidly coil and wrap tightly around the object. The coiling motion secures the plant to the support, pulling the weak stem upward toward the light.
Understanding Vining and Bush Varieties
The climbing habit is not uniform across all pea plants, which are bred into two distinct growth types: vining and bush varieties. Vining peas, also called indeterminate varieties, exhibit continuous growth throughout the season. They typically reach heights of 4 to 6 feet, sometimes exceeding 8 feet. These tall cultivars require significant, sturdy support to maximize yield and keep the plants off the ground.
Bush, or determinate, varieties are much shorter, generally growing only 1 to 3 feet tall. Their growth stops once they begin to flower. Although often labeled as requiring “no support,” these dwarf plants still benefit from a small trellis or cage to prevent the stems from flopping over. Popular pea types, including shelling peas, snow peas, and snap peas, are available in both tall vining and shorter bush forms.
Providing Support for Pea Growth
Support for vining varieties is necessary for maximizing the harvest and maintaining plant health. Allowing pea plants to sprawl on the ground significantly increases the risk of fungal diseases due to poor air circulation and prolonged moisture. Keeping the vines upright makes the pods easier to spot and pick, which encourages the plant to produce more peas over a longer season.
The support system must be installed when planting seeds or young plants to avoid damaging the shallow root system. Common supports include netting, wire mesh, or string strung between posts, often forming an A-frame or vertical trellis. Pea tendrils grasp objects best if they are relatively thin, generally less than a quarter-inch in diameter. For the largest vining peas over 6 feet tall, a robust structure like a cattle panel or strong wooden trellis is necessary to bear the weight of the mature, heavily laden plants.