The peanut (Arachis hypogaea) is a legume known for its unusual growth habit called geocarpy, where fruit development occurs beneath the soil surface. This underground maturation makes planting depth and specific soil conditions crucial for a successful harvest. Home gardeners often choose from four main types—Virginia, Runner, Spanish, and Valencia—each requiring a long, warm season. Achieving a plentiful crop depends on providing the optimal environment and following precise steps, particularly concerning how deep the seed is placed.
Preparing the Environment for Success
The foundation for a productive peanut crop begins with preparing the planting environment long before the seeds are sown. Peanuts thrive in deep, loose, well-draining soil, with sandy loam considered the ideal composition. This specific soil structure is necessary to ensure that developing peanut pods can form easily and that the plant’s fruiting structures can penetrate the medium without resistance.
Soil pH is another condition that requires careful attention, as it directly influences nutrient availability and plant health. Peanuts perform best in a slightly acidic to neutral range, with a target pH of 5.9 to 6.5. If soil tests indicate the pH is too low, agricultural lime should be incorporated to bring it into the optimal range, preventing nutrient deficiencies.
Timing the planting is governed by temperature, as peanuts require a long, frost-free growing season, typically a minimum of 120 days. The seed will only germinate reliably once the soil has warmed sufficiently. Growers should wait until the minimum soil temperature consistently reaches 65°F (18°C) at a 4-inch depth. For the best emergence and to minimize seedling diseases, waiting for the soil temperature to average a sustained 68°F (20°C) for three consecutive days is recommended.
Optimal Planting Depth and Spacing
The depth of planting is the most direct factor influencing germination and seedling survival. The recommended depth for planting shelled peanut seeds is consistently between 1 to 2 inches. Planting within this narrow window ensures the seed has adequate moisture for germination while remaining close enough to the surface for the seedling shoot to emerge quickly.
Sowing the seed too shallowly (less than 1.5 inches) exposes it to rapid drying and temperature fluctuations, which can kill the beneficial nitrogen-fixing bacteria. Conversely, planting deeper than 2 inches forces the seedling to expend too much energy pushing through the soil, leading to delayed or poor emergence. Most home gardeners plant the seed on its side, but planting the blunt, root-end downward can result in a more uniform emergence.
Horizontal spacing between individual plants is important for maximizing yield and accommodating the plant’s growth habit. For most varieties, seeds should be spaced approximately 6 to 8 inches apart within the row. The distance between rows varies based on the type of peanut being grown, as the four main varieties have different growth patterns.
Bunch-type varieties, such as Spanish and Valencia, have a compact, upright growth habit and can be planted in rows spaced about 24 inches apart. Runner and Virginia types, which tend to spread more, require greater space, typically needing row spacing closer to 36 inches (3 feet). Appropriate spacing allows for good air circulation, provides room for the pegs to develop, and facilitates the hilling process later in the season.
Post-Emergence Care: The Importance of Pegging
After the peanut plant emerges, it enters the reproductive phase marked by pegging. Small yellow flowers appear above the ground, and once pollinated, the petals drop off. The fertilized ovary then develops a thin, rigid stalk known as a gynophore or “peg.”
This peg elongates and arches downward, actively pushing into the soil surface. The actual peanut pod forms exclusively at the tip of this peg once it is buried. The peg must successfully penetrate the soil to a depth of about 1 to 2 inches for the pod to begin development and maturation.
The soil condition around the base of the plant is paramount, as the pegs cannot penetrate hard, compacted earth. To encourage successful pegging, gardeners should practice “hilling” by mounding soft, loose soil around the plant’s base. This provides an easy medium for the pegs to enter the ground.
Calcium application, typically in the form of gypsum, is needed directly on the soil surface around the plants at the time of flowering. Unlike most nutrients, the developing pods absorb calcium directly from the surrounding soil in the pegging zone, rather than through the plant’s root system. Supplying this element is necessary to prevent “pops,” which are pods with undeveloped or shriveled kernels.