Medicago sativa Seeds | Alfalfa
LATIN NAME: Medicago sativa
COMMON NAME: Alfalfa, Lucerne
Plant Profile
Alfalfa is the most widely grown forage legume in the world, and its garden value comes from the same traits that make it a farm crop: a deep root, rapid regrowth after cutting, and the ability to fix nitrogen. Medicago sativa is a perennial with three-leaflet leaves, small purple pea flowers and a habit that ranges from upright to sprawling depending on the strain.
It is an autotetraploid, with 32 chromosomes rather than the 16 of its diploid relatives, which gives it vigour and adaptability and makes genetics unusually complicated. The taproot can reach several metres in deep soil, which is the source of its drought tolerance and the reason it is difficult to transplant.
Science & Biotechnology
The root is the research subject. Alfalfa roots have been measured at depths of several metres, and the plant uses that access to survive long dry periods that kill shallow-rooted grasses. It also exudes compounds that influence the soil microbial community, and it accumulates more nitrogen in its tissues than most legumes, which is why it has been used as a green manure for centuries.
Alfalfa was also an early test case for genetic modification in perennial crops. Herbicide-tolerant alfalfa was approved in the United States in 2011 after a prolonged regulatory and legal argument about gene flow into conventional and organic production, since alfalfa is insect-pollinated and grown over large areas. The episode is still cited in debates about coexistence, and it explains why the crop appears in policy literature far more often than its acreage would suggest.
Uses & Benefits
As forage it is the backbone of the dairy industry: high protein, high digestibility, and multiple cuts a year. In the garden it works as a green manure, a nitrogen-fixing break in a rotation, and a drought-proof ground cover on poor ground.
The sprouts are the other familiar use, eaten raw in salads and sandwiches. They are nutritious and rich in vitamin K, though the seed also contains canavanine, an amino acid analogue that is reduced but not eliminated by sprouting. Alfalfa is not a significant medicinal herb in European practice, and claims about it beyond its nutritional value should be treated cautiously.
Growing from Seed
Alfalfa seed should be inoculated with the correct Sinorhizobium strain before sowing, particularly on ground that has never grown it; without the right bacteria the plants germinate and then yellow and stall. Sow 1 cm deep at 15-20°C in full sun, germination in seven to ten days.
It needs lime if the pH is below 6.5 and it hates waterlogging. Space plants 20-30 cm apart, or broadcast for a green manure and mow before flowering. Once established, cut it back two or three times a season to keep it leafy; left uncut it becomes stemmy and falls open in the middle.
Our Take
Grow it as a soil improver rather than a flower, and it will earn its space several times over. The purple flowers are a bonus, and a patch left to bloom will be visited by bees for a month.
Related Reading
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