Peanuts are not nuts

On Saturday I will be travelling to The Gambia, West Africa to spend three weeks working on a Girlguiding community project. I’m one of a team of 6 UK Girlguiding adult volunteers who will be training sessions with The Gambia Girl Guides to promote leadership, teamwork and advocacy. I’m very excited about the project, and since I haven’t been to Africa before I think it will be a really eye-opening experience. In honour of the project, the Organism of October is one of The Gambia’s main exports: the peanut.

Peanut (Arachis hypogaea) from Köhler's Medizinal-Pflanzen (image in the public domain)

Peanut (Arachis hypogaea) from Köhler’s Medizinal-Pflanzen (image in the public domain)

The peanut or groundnut (Arachis hypogaea) belongs to the legume family of plants. The name hypogaea means “under the earth”, and is a reference to the development of the fruit — called peanuts — under ground. The flowers develop above the surface, but after they are fertilised the flower stalk lengthens, sending the the ovary containing the developing fruit underground. This develops into a peanut containing 1-4 seeds.

Peanuts have a variety of uses as food (raw, cooked in dishes, ground nut oil), but they can also be made into solvents and used in medicines and textiles. They are rich in nutrients including niacin, folate, fibre, vitamin, magnesium and phosphorous. Like soybean and other legume crops they are rich in protein (about 25% dry weight). The peanut was probably first cultivated in Paraguay, where its closest wild relatives still live. Today the major producers of peanuts are the US, Argentina, Sudan, Senegal and Brazil.

Prior to the arrival of the peanut in West Africa, local people cultivated a closely-related native legume called the Bambara groundnut, which is similar to the peanut, both in terms of how it grows and its uses in cooking.

Peanut seeds surrounded by their pod. Image by Texnik (CC BY-SA 3.0 via Wikimedia Commons).

Peanut seeds surrounded by their pod. Image by Texnik (CC BY-SA 3.0 via Wikimedia Commons).

Despite the name, a peanut is not actually a nut. In botanical terms, “nut” specifically refers to a fruit that has a hard outer casing that does not split when it ripens, for example an acorn or chestnut. The outer casing of a peanut is the equivalent of the pod found on other legumes (for example peas and beans). In most legumes, when the fruit matures the pod splits open along two lines of intrinsic weakness to release the seeds inside. Peanuts are one of the exceptions to this, perhaps because their fruits develop underground, but they do share the same core fruit structure as the other legumes (click here for some cool diagrams).

Time to get back to my packing! While I am away, my friend (and guest blogger) Kirsty will be looking after the site and posts will be still be published as normal so please keep reading!

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One thought on “Peanuts are not nuts

  1. Pingback: Peanuts are not nuts | Plant-Microbe Symbioses ...

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