Peanuts

I started my journey growing peanuts when something emerged from a planting container that I hadn’t planted. And it was unmistakably a peanut.

An unexpected peanut

The only thing I could figure was that one of my local scrub jays had ‘planted’ it for later consumption. At the time, I had no bandwidth for growing peanuts. So I dug it out to take a closer look at the root system. [Now I let them grow!]

Immature peanut plant

Nuts that are not nuts​

Peanuts, also known as goobers, or groundnuts, are legumes. This means that they are able to ‘fix’ atmospheric nitrogen into a form they can use as food, with a little help from certain bacteria that live on or in their roots. The botanic name, Arachis hypogaea, describes a legume that produces its seeds “under the earth”, in a behavior called geocarpy. Geocarpy is rare in the plant world. It is a means of reproduction in which pollinated flowers are transformed into specialized stems, called pegs. Pegs are budding ovaries that bend downward and push their way into the soil. Seeds are produced along these pegs. Unlike other plants, which produce seeds above ground for easy dispersal, the peanuts we eat are the underground seeds of the peanut plant. And they are not nuts at all.

Peanut pegs growing into the soil (H. Zell) CC BY-SA 3.0

Parts of a peanut

If you look closely, it is easy to see how peanuts are related to peas and beans. They have very similar seed structures. Each delicious peanut has five parts:

• the papery outer shell
• cotyledons - the part we eat
• seed coat - the papery coating that surrounds the cotyledon
• radicle - that little nub (an embryonic root) that sticks out from between the halves of a cotyledon
• plumule - the tiny shoot emerging from the radicle

Peanut seeds (Jeusorizales) CC BY-SA 3.0

Peanut varieties

Peanut plants come in two forms: runners and bush. Bush varieties are 18 to 22 inches tall, while runners can spread out 28 to 31 inches. Peanuts are believed to be a human construct, through artificial selection between two wild varieties. This occurred in Argentina or Bolivia, nearly 8,000 years ago. Selective breeding of this first peanut has resulted in six major and two minor landraces. A landrace is a regional, domesticated variety. These groups are:

• Runner - grown in Georgia; higher yield, better flavor, and a better roaster than Spanish
• Spanish - grown mostly in Texas, Oklahoma, and New Mexico; highest oil content
• Tennessee - similar to Valencia, but stems are green and kernel production  is lower
  • Tennessee Red - red kernels
  • Tennessee White - white kernels
• Valencia - grown in west Texas and New Mexico; taller than other varieties (49 in.); used boiled
• Virginia - grown in Virginia, Texas, and much of the southeaster seaboard states; large seeds

Until the 1930s, peanuts were used predominantly as a livestock feed. That was when the USDA actively promoted peanuts as a commercial crop for human consumption.

How to grow peanuts

While it’s true that peanuts prefer the sandy loam of the southeastern U.S., peanuts can be grown in raised beds and large containers that are filled with a lightweight potting soil. You can start peanuts in a tray filled with potting soil. Make one inch deep holes by hand or with a dibble, and drop one shelled peanut into each hole, cover with soil, and water well.

Over the next couple of weeks, as you are waiting for your peanut seeds to germinate, prepare the planting bed by incorporating lots of aged compost. This will help lighten compacted soil and add important nutrients. You can up-pot your peanut seedlings into larger containers, or transplant them to their bed when they are a few inches tall. This is where it gets interesting.

​When you first place your peanut plants, you will want to install them in a sunken trench in the bed, and mound soil around the plant all the way to up the stem, to just underneath the top set of leaves. From that point on, just leave them alone. No peeking! For the next 4 or 5 months, underground and out of sight, your peanut plants will be busy storing up starches and sugars for next spring’s crop. (Or your autumn harvest!) Before that time, however, there are certain pests and diseases that you must watch for.

Peanut pests and diseases

Peanut plants are host to several fungal diseases, including sclerotinia blight, leaf spot, stem rot (white mold), rust, web blotch, diplodia collar rot, rhizoctonia limb rot, black rot (CBR), and crown rot. Tomato spotted wilt, a viral disease, and root knot nematodes can also cause problems. Weevils, wireworms, leafhoppers, whiteflies, thrips, cutworms, and some caterpillars are considered major pests of peanuts. Of course, birds, squirrels, and voles are going to want some of your harvest, as well.

​Harvesting peanuts

Infographic courtesy of Insteading.com

In commercial peanut fields, as peanut plants begin to yellow, machinery is used to dig plants out of the ground, give them a good shake, and then flip them over and leave them on the soil surface for a few days to dry. In the home garden, you will harvest your peanuts by simply pulling the plants out of the ground, giving them a good shake to get rid of any clinging soil, and leave them, upside-down, to dry for a few days. [You may want to do your peanut drying in the garage, to protect your harvest against marauding birds and squirrels.] Next, peanuts are threshed, or removed from their stems. You may be surprised to learn just how important the drying aspect of peanut harvesting is - peanuts stored with too much moisture can become infected with a fungus (Aspergillus flavus) that produces toxic substances that can be carcinogenic. Be sure to dry your peanuts thoroughly!

Mature peanuts (Pollinator) CC BY-SA 3.0

Peanuts, like other legumes, are an excellent crop rotation choice. Not only are they able to fix atmospheric nitrogen, they also help improve soil structure and soil health.

So, plant a peanut and see what happens!

Peanut flower (SKsiddhartthan) CC BY-SA 4.0