Clover quietly nearly tripled European farm output before chemical fertiliser existed
Between 1750 and 1880, European farms came to produce about 275 percent of their earlier output, and one humble plant deserves much of the credit. Clover pulls nitrogen from the air and feeds it into the soil, replacing what cities were carting away as food.
Trifolium, Latin for three-leaf, is a genus of roughly 300 species in the legume family. The plants rarely top 30 cm and carry small heads of red, purple, white or yellow flowers. They began in Europe but now grow worldwide, most diversely in the temperate north yet also high on tropical mountains in Africa and South America. White and red clover are the most widely farmed.
Spain domesticated clover around the year 1000. The secret is bacteria living in nodules on its roots, which fix atmospheric nitrogen. As Europe urbanised, rotating clover through fields became essential for restoring the nitrogen shipped off in crops. Clover also made good fodder and silage, regrowing after repeated mowing, and until the mid-20th century it was the main nectar source for honeybees. Colonists spread it globally, and some species turned invasive. Grown too often in the same field, though, it succumbs to clover sickness, a mix of pests, disease and nutrient imbalance, which is why rotations space it at least eight years apart.
Imported guano and then the Haber-Bosch process for making ammonia pushed clover aside in the 20th century, to the detriment of pollinators. Since industrial nitrogen takes a great deal of energy, its price follows energy costs, and roughly doubling prices in the 1990s and 2010s revived interest in clover mixes. Bumblebees pollinate clover best, and their decline under intensive farming makes clover a candidate for helping pollinators recover.
Culturally, the shamrock is often linked to clover, though some say it is an Oxalis. Four leaflets are famously lucky, and more are rarer still. Collectors in Japan keep raising the bar: Shigeo Obara found clovers with 18, 21 and then 56 leaflets, and on 2 August 2023 Yoshiharu Watanabe set the record at 63. The shape of cloverleaf motorway junctions nods to the plant.
Source: Clover
