Many people are not aware that peanuts grow underground, and not on trees like walnuts or pecans, but underground.
Another surprising fact is:
Peanuts are not classified as a nut.
But the word “nut” is in their name?
The botanical meaning for “nut” is a fruit’s ovary wall becomes hard as it matures. By this definition, the peanut is not a typical nut.
Peanuts are classified as legumes, which is part of the bean and pea family. Called forage legumes, peanuts have an edible seed that grows in a pod. One difference from other legumes is that you do not eat the pod like you would a soybean or green bean. Technicality aside, they are still referred to as “nuts” in the culinary world and their name.
It makes for an unusual crop because the plant flowers above ground as the peanuts mature below the surface, hence the name “groundnut” which is another name for the peanut. Places such as Nigeria, India, and the Southern United States are ideal locations to grow peanuts. Peanuts are best planted in the early spring when there is no threat of frost or a decrease in temperatures. Soil temperature is important. The soil needs to reach 65 degrees Fahrenheit before planting. To yield a good crop, you will need between 120 and 140 days of warm weather leading up to the fall when they are ready to be harvested. This is important to consider since the growing season starts in early spring and fall when temperatures can drop unexpectedly. If growing conditions are ideal between 90 to 150 days of planting, depending on the species. Planting of subspecies A.h. fastigiata require 90-130 days, and A.h. hypogaea require 120-150 days for harvest. If the growing seasons are long enough, subspecies A.h. hypogaea is a preferred crop for growers since it yields more.
The soil also needs to be well cultivated and rich in calcium. The soil also requires adequate levels of other micronutrients like potassium, phosphorous, and magnesium. Drainage is critical to ensure that the soil does not stay wet and risk ruining the crop. Peanuts can be grown in as little as 14 in of water, with better yields at 20 inches of rain. The level of pH is essential as well. It fares best between the levels of 5.9-7. Peanuts do not require any nitrogen-containing fertilizer since they are able to fix nitrogen with the aid of a rhizobium bacteria. This also helps with soil fertility. The ability to fertilize the soils is a big reason why farmers consider peanuts valuable in crop rotation. Not only is the yield of a peanut crop itself is increased, but other y crops as well.
Peanut varieties that will work best for the home gardener would be “Virginia Improved” and “Early Spanish.”
The plants start to show in the form of bright yellow flowers about 30 to 40 days after the initial sprouting. After fertilization, the flowers will droop towards the ground. The fertilized flower, now called a peg, will take about ten days to penetrate the soil, start to enlarge and form a peanut. The plants will continue to produce flowers as pods are forming. This makes the timing of the harvest crucial. If the plant is pulled to soon there may still be some unripe peanuts; if pulled too late, the pods will snap off the stalk and remain in the soil. This can ruin a crop and reduce a grower’s yield. When removing the plant, the whole plant is removed, including the roots. Covering the pods is a network of raised veins which are constricted between seeds.
Peanut harvesting begins in the fall. Remember, when harvesting peanuts, the whole plant needs to be removed. There are two ways to harvest them.
One is the traditional way where the peanuts are pulled out by hand. When pulling the peanuts if you notice the interior of the pod is dark, that is a sign of over-mature peanuts, which would be no good for boiling but still good to dry roast.
The second is by using machinery.
Pull one plant to inspect before pulling the whole crop. This way, you will be able to tell if the entire crop is ready to be harvested.
The plants need to be harvested immediately if the plant has lost most of its leaves or the hull aren’t firmly attached to the plant.
This method uses a machine to cut off the main root of the plant. The machine cuts through the soil, just below the peanut pods — the machine then lifts the plant from the ground and then shakes it. Then the plant is flipped upside down, keeping the peanuts out of the soil. Inverting the plants will allow the peanuts to slowly dry to a little under a third of its original moisture level. The drying process takes between three and four days.
It is crucial that the peanuts are mostly dry before they are removed. If left moist or stored in poor conditions, the peanuts are susceptible to becoming infected with Aspergillus flavus, a mold fungus. This strain of fungus releases aflatoxins, a highly carcinogenic substance.
The threshing process begins after drying. The process of threshing is when the peanuts are separated from the vine using a combine machine. The peanuts are blown into special hoppers. The peanuts are placed into a dumping wagon where warm air is forced through the wagons ring the peanuts. Then the peanuts are brought to a buying station where the peanuts are then inspected and graded for sale.