Of all the food plants you might grow in your summer garden, none are more interesting than the peanut. Its botanical name gives important hints about the adventure ahead: Arachis indicates that the plant has the rare habit of ripening its pods underground. Hypogaea translates as "underground crypt." Sure enough, peanuts develop their seeds tucked up into a cluster beneath the plants' crowns, so they really are ground nuts.
It's a quirky life cycle that's great fun to watch, plus you get to eat garden-grown peanuts. Peanuts grow best in sandy soils in warm climates, but any gardener with a growing season lasting more than 120 days can grow a hill or two, just for fun. There is no need to rush. Peanut seeds will not germinate until soil temperatures reach 65°F (18°C), so even in warm climates they are not planted until late spring or early summer.
In the US, Southern Exposure Seed Company sells several peanut varieties, including fast-maturing Valencia and Spanish types. These are the best types to grow in a garden because they mature in 110 days, three weeks faster than other types, and they have an upright, bushy growing habit.
If you can find some raw peanuts in the shell, by all means plant a few. Most raw peanuts intended for cooking at home are Valencia or Spanish types. Ideal peanuts for planting are still in their shells, but shelled raw peanuts with their skins intact may be strong germinators, too.
Also look for peanut plants at local nurseries. Even in the UK, many garden centers have started selling peanut plants.
How Peanut Plants Grow
Native to Brazil, peanuts probably adopted their odd reproductive strategy as a way of persisting in sandy soil where drought and wildfires were a constant risk. Plants that develop seeds underground are naturally resistant to predators, fire and dry weather. Here's how the peanut show goes.
About six weeks after they seeds sprout, peanuts plants produce pea-like yellow flowers on fleshy stems. Once fertilized, the flowers slowly bend down until they penetrate the soil, a process called pegging.
Once underground, the pegs move sideways to form a cache of ripening nuts under the crown of the plant (hence the "underground crypt" part of the botanical name).
This flowering and pegging goes on for more than a month, and meanwhile the plants grow into sprawling bushes. When the plants finally begin dying back, or before the first frost, the plants are pulled up, roots and all, during a period of dry weather.
After shaking off the soil, peanut plants can be dried in the sun or in a dry building, root sides up. A few days later, you pick off the nuts and sort them by size.
Because peanuts bloom and set pegs for a long period of time, harvested plants often bear nuts at different stages of ripeness. Small, immature peanuts can be scrubbed, boiled in well-salted water until soft and eaten as a snack, like edamame.
Medium-size nuts can be set aside for eating fresh, and the biggest nuts with hard shells can go into cool storage.
Growing Peanuts in Containers
Novelty crops like peanuts are fun to grow in containers because you can watch them up close. And, in cool climates, peanuts may do better in large, dark-colored containers than in the garden because their roots will stay warmer.
Spacious quarters are needed to accommodate the pegging process, but a pot or planter at least 12 inches (30 cm) deep and 18 inches (46 cm) across will meet the needs of one robust peanut plant.
While the plant is small, the outer sections of the pot or planter can be used to grow a quick crop of lettuce, radishes or cilantro.
Peanuts are nitrogen-fixing legumes, but they still need fertile soil in the garden, and periodic feeding when grown in containers.
Once the containers fill with roots they often need daily watering in warm weather, too. Yet peanuts are anything but finicky. Growing peanuts in sun-warmed pots or beds sets the stage for a fascinating botanical show, with a great snack afterward.
By Barbara Pleasant