Ever-popular peanuts are actually not nuts at all, but the underground seeds of a tropical legume plant related to peas and beans. And peanuts have a truly unique growing habit. While the yellow flowers bloom above ground in traditional fashion, the fruit and their seeds develop at the end of live shoots called "pegs," which grow down into the ground. The peanut clusters are the fruit that forms at the ends of these pegs.
Peanuts have a long growing season and are most often grown in warmer climates, but you can try your hand at growing them indoors. These annuals are normally planted from seeds (shelled peanuts) in the spring after the last frost and harvested in the early fall. They require as much as 150 days to produce edible peanuts, but there are early maturing varieties that require less than 100 frost-free days.
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|Common Name||Peanuts, goobers|
|Botanical Name||Arachis hypogaea|
|Mature Size||1–2 ft. tall, 3 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Sandy, loamy|
|Hardiness Zone||2–11 (USDA)|
|Native Area||South America|
Growth Stages of a Peanut Plant
The National Peanut Board outlines the following stages in the planting, growth, and harvest of peanuts:
- Planting. This occurs after the last frost, sometimes in April through May, when soil temps have reached 65 to 70 degrees Fahrenheit. Planting depth is about 2 inches deep, 1 to 2 inches apart, in rows that will facilitate harvesting.
- Peanut cracks the soil. Seeds sprout and send shoots up out of the soil about 10 days after planting.
- Flowers appear. When plants are about 18 inches high, they produce flowers. This occurs about 40 days after planting.
- "Pegs" extend into the soil. From the flower's ovary, the plant sends down a fruiting "peg" which will penetrate the soil, then turn sideways to begin its transformation into a pod with seeds inside. Within four to five months of planting, each individual plant may "peg" as many as 40 pods.
- Plants are harvested. About 140 to 150 days after planting, the plants are dug up entirely from the ground, stems along with the underground seed pods.
- "Combining" separates peanuts from stems. After the plants have dried (when the water content drops to about 10 percent), the peanut pods are separated from the stems and are ready to eat or to store for future use. Commercially, this is done by large machines known as "combines."
If you live in an area where summers are long and warm with at least 120 to 150 frost-free days, you are in the right location to grow peanuts. For this reason, peanut plants are most productive in USDA hardiness zones 8-11.
Once seeds go in the ground, keeping the area around the peanut plants weed-free and loose is very important to produce healthy pegs. After the plant has flowered and has been pollinated, it will start sending pegs into the soil. Adding a couple of inches of mulch when the plants grow to about a foot tall helps with weed control and keeps the soil soft enough for pegs to penetrate.
After the pegs have entered the soil, do not disturb them. You might see lots of flowers on the plants but only 15 percent of them will actually send a peg into the soil and grow peanuts.
Peanuts need full sun for at least eight hours per day.
Peanuts grow best in loose, well-drained, sandy loam with a slightly acidic soil with a pH range of 6.0–6.5 . Avoid poorly drained and hard clay soil. Do not plant peanuts in the same space where you have grown other legumes (beans or peas) in previous years.
Peanuts need about 1 inch of rain or irrigation per week during the growing season. Watering is most critical immediately after planting, to ensure germination and establishment of the seedlings, then again 60 to 110 days after planting when the pegs have entered the soil and are filling with peanut clusters. Stop watering the plants 10 days to two weeks before harvesting.
When watering, avoid wetting the leaves and use drip irrigation if possible. The soil should be moist but not saturated.
Temperature and Humidity
The ideal growing temperature for peanuts is between 86 and 93 degrees Fahrenheit. Higher temperatures may lead to flower damage.
Slightly humid conditions are good while the plants grow but a period of dry weather is needed before the harvest.
Peanuts need calcium in the upper 6 inches of the soil where the pods grow. Amendment with bone meal or another source of calcium at the time of planting can help with this.
Peanuts are a legume that fixes its own nitrogen in the soil if rhizobium bacteria are present. Therefore peanuts do not need additional nitrogen fertilizer. However, if you plant them in a location where peanuts have never been grown before, it might be a good idea to add a peanut inoculant to the soil at the time of planting which stimulates the roots to grow the nodules that fix nitrogen in the soil.
Note that peanuts are extremely susceptible to fertilizer burn, so if you do feed, do so before seeding and make sure to thoroughly work any fertilizer into the soil.
Types of Peanuts
- Valencia peanuts are the quickest to mature in 90 to 110 days. It is therefore often the variety preferred by home gardeners. They have three to five relatively small kernels per pod, with pretty red seed coats.
- Spanish peanuts take 90 to 120 days to mature. The peanuts are mainly used for candy and roasted peanuts.
- Virginia peanuts and runner peanuts both require about 130 to 150 days to mature. This variety produces a high yield of large pods. As their name indicates, runner peanuts need more space, about 3.5 feet per plant. The fruit is small, with two kernels per pod. They have excellent flavor and are most commonly used for peanut butter. Both Virginia and runner peanuts are intolerant of cool temperatures and drought.
How to Grow Peanuts From Seeds
Shelling ordinary raw, uncooked peanuts gives you the seeds necessary to grow peanuts. Raw grocery peanuts can work for this, though it's better to buy your seed peanuts from a garden center.
- Sow seeds directly outdoors after the last frost.
- Remove the seeds from their shells before sowing. But be very careful not to remove or damage the tender skin on the seeds or the seeds won't germinate.
- Plant the seeds 1 to 2 inches deep, 4 to 6 inches apart.
- Leave 3 feet between the rows.
- Keep the soil moist to ensure germination.
- Seeds will germinate in 10 to 15 days.
- Thin the seedlings when they are about 2 inches tall, to a spacing of 8 to 12 inches.
- As the plants grow to about a foot tall, "hill" them by heaping additional soil around the base of the stem, along with light mulch for weed control. The hill accommodates the peg.
- Pegs grow from the faded flowers and push into the soil about 1 to 3 inches.
Several signs will tell you that peanuts are ready to be harvested in late summer or early fall. The most obvious is yellowed foliage, but you should also pull a couple of pods from the ground and inspect them carefully. Ready-to-harvest pods have the typical veined surface, the seed coats are colored, and most of the pods have a darkened inside surface. When you harvest the peanuts, the soil must be dry.
- Dig or pull the entire plant from the ground and gently shake it to remove excess soil.
- Hang the plants with the peanuts attached in a dry, warm location with good air circulation.
- Leave them to cure for about one week.
- After curing, shake the soil from the pods.
- Remove the peanuts from the vines.
- Continue to air-dry the peanuts for another week or two.
Common Pests & Plant Diseases
Peanuts can be affected by a wide range of pests and diseases, especially hungry squirrels, mice, and chipmunks (secured mesh row covers can help here). Leaf-feeding insects may include armyworms and caterpillars. Common diseases are leaf spot, rust, blight, and viral diseases. To help identify what is harming the plants, seek assistance from your local university extension office. They will also suggest the best remedies for the ailments.