Arachis pintoi aka Pinto Peanut

Arachis pintoi, or pinto peanut, belongs to the pea family. It comes from central and eastern Brazil. There, it grows in low forest with dense tree cover. This wild kin of the peanut is a herbaceous perennial. This means it has soft stems and lives for years. Growers use it in tropical pastures and under plantation trees.

Plants form a low, dense mat as they age. Sources give usual heights of about 0.7–1 foot [0.2–0.3 metres]. Stems first trail along the ground, then turn upward. In dense stands, they may reach 1.6 feet [0.5 metres]. Young plants spread through stolons, or stems along the ground. Older crowns form strong taproots. Plants can last in pasture for more than 20 years. In wet tropical sites, stolons may spread 6.6 feet [2 metres] yearly. In subtropical sites, yearly spread may reach 3.3 feet [1 metre].

Pinto peanut suits moist tropical climates and humid subtropical ones. It grows best in light shade but tolerates sun and deep shade. It prefers rich ground, yet also grows in poor soil. It can grow in sand, loam, and clay. It grows best where water drains well. Still, it can cope with some waterlogged soil. It prefers acidic soil, with a pH of 5.4–6. It tolerates a wider range of 4.5–7.5. Moist soil helps it grow, but it can endure four dry months. Best daytime temperatures fall between 22 and 28°C. Frost kills the shoots. Roots may recover after light frost.

Insects pollinate the flowers, and the seed forms underground. Hard clay or a crusted surface can block growing pods. These soils then stop the plant from making seed. Fresh seed has strong dormancy, a state that delays growth. Warm drying can reduce this delay. Growers can also grow plants from cuttings. In new areas, seed needs a specific Bradyrhizobium strain. The strain used for commercial peanuts does not suit it.

The plant fixes nitrogen, which helps improve soil. Growers use it for forage, hay, and green manure. They also grow it as ground cover for its looks. It withstands heavy grazing and grows with strong pasture grasses. It copes with shade, so it suits sites under tree crops. Once plants take hold, they can be hard to remove. Yet sources report no weed problems. The supplied sources list no known uses as human food or medicine. They also report no known hazards.