The bean family, also known as the legumes, leguminoseae or papilionaceae. One of my favourite plant families. Their flowers are beautiful, very distinctive and pleasingly perky; and I like seed pods that really look like pods. There’s also something charming about the unfolding, trefoil leaves at the end of every branch, and I’m a fan of plants with tendrils.
On top of all that, their specially adapted root nodules house nitrogen-fixing bacteria, producing nitrogenase to draw unreactive nitrogen from the atmosphere and transform it into compounds that other plants can use. Before the Haber-Bosch process was invented we had to rely heavily on legumes and lightning to get our nitrogen fix. This is why crop rotation usually includes a phase where fields are planted with legumes.
As well as peas, the family includes all kinds of beans, lentils and peanuts. Making protein requires nitrogen, so most protein-rich plant-based foods are either legumes or the seeds of larger plants, like nut trees. Unfortunately, the seeds of legumes are also rich in oligosaccharides, complex carbohydrates that humans cannot digest, but which our gut bacteria can – producing methane and other gases. Besides the food crops, legumes also include broom, gorse, clover, vetch, laburnum and lupins.