Arachis hypogaea (Peanut Plant)

Arachis hypogaea, commonly known as the Peanut Plant, is a unique plant that produces flowers above the ground, but its fruits, the peanuts, develop underground, a phenomenon known as geocarpy. This interesting feature makes peanuts a botanical curiosity and a popular subject of study in agriculture. Considering this characteristic, the botanist Carl Linnaeus gave peanuts the specific name hypogaea, which means "under the earth".

Peanuts belong to the botanical family Fabaceae (or Leguminosae), commonly known as the legume, bean, or pea family. Like most other legumes, peanuts host symbiotic nitrogen-fixing bacteria in root nodules. The ability to fix nitrogen means peanuts require less nitrogen-containing fertilizer and improve soil fertility, making them valuable in crop rotations.

Peanuts are valued for their high content of proteins, healthy fats, B-complex vitamins, and essential minerals, making them a nutritious snack and a versatile ingredient in cooking. The plant needs a warm climate and well-drained soil to thrive, preferring regions with long, warm summers.

In gardening, Arachis hypogaea can be grown as an interesting and educational addition, offering home gardens not only useful fruits but also the opportunity to observe a fascinating growth cycle. This plant is relatively easy to grow and can be a satisfying source of home harvest, adding value and diversity.

Appearance of leaves, flowers, and fruits

• Leaves: The leaves are compound, paripinnate, made up of 2-3 pairs of oval leaflets, of a medium green color, measuring 3-7 cm long. They are arranged alternately on the stems, with a smooth texture and entire edges.
• Flowers: The flowers are small, yellow, typical of legumes, with butterfly-shaped petals, 1-1.5 cm long. They appear in June-July at the leaf axils, being self-fertile but can attract bees for pollination. After pollination, the flower stalk (called a “peg”) elongates and penetrates the soil, where the fruits form.
• Fruits: The fruits are underground pods, 2-6 cm long, with a woody, yellowish shell, containing 1-4 seeds (peanuts). The seeds are oval, covered by a thin, reddish shell, and are rich in oil (40-50%) and proteins (20-30%). Harvesting occurs at 90-150 days after planting, depending on the variety.

Growth characteristics

• Height and width: Grows up to 30-60 cm tall and 60-90 cm wide, with an upright or trailing habit depending on the variety (e.g., “Virginia” varieties are upright, “Runner” are trailing).
• Vigor: Moderately fast growth, with branched, slightly hairy stems. The root system is taprooted, with nodules that fix nitrogen, enriching the soil.
• Type: Annual herbaceous plant, grown in 4-5 month cycles, sensitive to frost.

Growing conditions

• Exposure: Prefers full sun (6-8 hours/day) for optimal development and maximum yield. Shade reduces flowering and pod formation.
• Soil: Requires loose, well-drained soil, preferably sandy or loamy, with a slightly acidic to neutral pH (5.8-7). Compact or heavy clay soils hinder the penetration of the pegs into the soil.
• Watering: Water regularly, keeping the soil moist but not waterlogged, especially during flowering and pod formation (July-August). Reduce watering towards the end of the cycle to facilitate harvesting.
• Temperature: Grows well at 20-30°C, sensitive to temperatures below 10°C or above 35°C. Hardy in zones 8-11, requiring a warm season of at least 120 frost-free days.

Care and resistance

• Resistance: Sensitive to frost and prolonged drought. Resistant to some fungal diseases but can be affected by leaf mold (Cercospora) or root rot (Rhizoctonia). Attracts pollinators but is not resistant to deer or rodents.
• Fertilization: Apply a fertilizer low in nitrogen (e.g., 5-10-15) at planting and during flowering, as the plant fixes nitrogen naturally. Excess nitrogen promotes foliage at the expense of pods.
• Pruning: Does not require pruning, but remove weeds to prevent competition for nutrients and space.
• Pests and diseases: Can be affected by aphids, mites, caterpillars, or nematodes. Use organic insecticides and crop rotation for prevention. Inspect for mold or leaf spots.
• Propagation: Propagated by seeds (raw, unroasted peanuts), planted 5-7 cm deep, spaced 15-20 cm apart, in spring after the soil reaches 18°C.
• Harvesting: Harvest when leaves begin to yellow (September-October), lifting the plant with a fork. Dry the pods for 2-4 weeks in a well-ventilated place.

Uses

Arachis hypogaea (Peanut Plant) is grown for its edible seeds, consumed raw, roasted, in peanut butter, oil, sweets, or fodder. It is an important source of proteins, healthy fats, and vitamins (E, B). The plant is used in farm gardens, farms, or test crops in home gardens, being attractive for its nitrogen-fixing ability. It pairs well with corn or cotton in crop rotations. In landscaping, it is rarely used ornamentally but can serve as an educational element.

Origin

Native to South America, Arachis hypogaea was domesticated 7,000-8,000 years ago by the indigenous peoples of Bolivia and Paraguay. It spread to Africa, Asia, and North America during colonization, becoming today the second most important oil legume after soy.

Height including pot: approx. 20 cm
Pot diameter: 12 cm