Peanut Root Growth

Root System

• In peanut seedlings, a primary root grows quickly and forms a taproot, which absorbs moisture from deep soil layers. This central root becomes large and thickened as it develops. Long, thin, lateral roots begin growing soon after germination. As the plant develops, smaller, hair-like roots that work as feeder roots grow from the lateral roots. Throughout the root system are nodules that perform nitrogen fixation and often form at root hairs or at the intersection of lateral roots. Peanuts themselves form in pods on shoots that turn into the soil and lie next to the roots.

Nitrogen-Fixing Nodules

• Like all legumes, peanut plants perform nitrogen fixation with help from rhizobial bacteria in their root nodules. The structure of root nodules blocks oxygen from entering this part of the root, as oxygen can restrict nitrogen development. Bacteria within the nodules convert atmospheric nitrogen into ammonia. Other bacteria produce useable nitrates from the ammonia and provide them to the plant to help it grow.

Peanut Development

• Peanuts are seeds that develop within pods. Initially, flowers are self-fertilized above ground, but the developing ovaries, or pods, turn downwards into the soil to finish developing. The plant grows a tip or peg that encourages the pod to root into the ground and protects it like a root cap. Once it is a few centimeters deep, the peg stops developing and the pod becomes parallel with the ground. Eventually, two mature peanuts will be harvested from each pod, dried and blanched for use in various desserts and dishes.

Peanut Harvest

• Expect peanut plants to pursue a growth cycle lasting about four to five months. Around 30 to 40 days after planting, bright yellow flowers will grow. They penetrate the soil about 10 days after being pollinated. Mature peanuts are ready for harvest nine to 10 weeks later. Often, a large part of the root system is removed along with around 40 or more pods present on each plant.

  50 percent of U.S.-grown peanuts are turned into peanut butter. Otherwise, they can be roasted and salted for snacks, made into chocolates and other sweets, used in baked goods or included in meat and stir-fry dishes.