Alfalfa (lucerne)
Medicago sativa
Botanical family: Fabaceae
Medicago sativa, grown for millennia as a fodder plant, is one of the Fabaceae richest in fixed nitrogen per hectare. In permaculture, it's used as a temporary meadow or a mown strip to feed the soil before a demanding crop, or as a fertilising liquid manure.
Full sun
Chalky, deep, well-drained
Undemanding once rooted (a very deep taproot)
Hardy perennial, withstands -25 °C depending on variety
Overwinters in your zone
Role in permaculture
A reference fodder plant since antiquity, alfalfa captures nitrogen from the air and draws water from the deep horizons thanks to its taproot; it is also an excellent nectar plant.
Poor companions
Allelopathy, reputed or observed: may slow some neighbours
Insects attracted or useful
Documented synergies
Relationships backed by a named source, with their real scope. A synergy without a named reference has no place here, no “it is said that…”.
It fixes atmospheric nitrogen by nodulating with this bacterium of its own, distinct from that of clover or pea. The mechanism is certain; the field magnitude very variable with soil, strain, and climate, and no precise figure for it is cited here, as the measurement could not be read at the source. The benefit to a neighbouring plant comes mainly through return (mulch, residues, death of the nodules), not through a guaranteed direct transfer.
institutional source
- · Carlsson G. & Huss-Danell K. (2003), Plant and Soil 253:353-372, DOI 10.1023/A:1024847017371
Alfalfa has the deepest root of a set of eleven temperate crops, nearly 1.8 m, which structures the soil at depth and exploits the water of the lower horizons. But beware of the myth: the authors specify that more than half of its root mass stays in the first 20 centimetres. 'Deeper' does not mean it massively brings nutrients up from the subsoil to the surface.
scientific study
- · Fan J., McConkey B., Wang H., Janzen H. (2016), Field Crops Research 189:68-74, DOI 10.1016/j.fcr.2016.02.013
Alfalfa produces compounds (saponins, phenols) that slow germination, including its own. That's the agronomic reason never to resow alfalfa right after alfalfa: a rotation interval is needed. The 'weedkilling' effect on neighbouring plants, for its part, is only demonstrated in the laboratory (germination dish), not a proven effectiveness in the garden.
scientific study
- · Ghimire B.K. et al. (2019), Plants 8(7):233, DOI 10.3390/plants8070233
A strip of alfalfa attracts Lygus bugs away from a sensitive neighbouring crop, but with a crucial condition: the trap alone only CONCENTRATES the pests. Damage reduction is obtained only by actively removing the bugs (mechanical vacuuming); without that, the strip becomes a reservoir. Demonstrated in a very specific context (organic strawberry in California), not to be transposed as-is to the kitchen garden.
scientific study
- · Swezey S.L., Nieto D.J., Bryer J.A. (2007), Environmental Entomology 36(6):1457-1465, DOI 10.1603/0046-225X(2007)36[1457:COWTPB]2.0.CO;2
Seasons & availability
Lucerne is sown in spring, in March and April, and in late summer, in August and September; a perennial legume rich in nectar, it covers the soil from spring to autumn, then is cut and dug in before flowering as a nitrogen-rich green manure.
Available: April, May, June, July, August, September, October, November.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Plants For A Future, « Medicago sativa » (pfaf.org/user/Plant.aspx?LatinName=Medicago+sativa)
- Arvalis, « Réussir l'implantation d'une luzerne » (arvalis.fr/infos-techniques/reussir-limplantation-dune-luzerne)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Rinse raw sprouts (bacterial risk) and reserve them for people who are not vulnerable. Alfalfa contains L-canavanine, which is not advised in cases of lupus or autoimmune disease.
Family behaviour: Legumes
In general, Legumes fix nitrogen from the air in most cases, thanks to the Rhizobium in their root nodules. They mainly enrich the soil for the following crops, as their residues decompose. Ideal in a rotation, before nitrogen-hungry plants such as nightshades.
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Species & varieties
The best-known species and varieties in France.
Species
Voices of peoples
Paraphrases attributed to their documented sources. Never an invented quote.
Pliny the Elder, Roman naturalist · Rome, 1st century AD (reporting an event set at the Persian Wars, early 5th century BC)
In his Natural History, Pliny the Elder notes that alfalfa, which he calls medica, is foreign even to Greece: it is said to have been brought there 'from the land of the Medes' during the Persian wars led by Darius. Its Latin name, medica, keeps the trace of this Median origin, the 'plant of the Medes'. This is a naturalist's note on the circulation of a forage, not a myth. One must, however, read in it the origin as it was imagined in Rome, and not the real itinerary of the species.
Pline l'Ancien, Histoire naturelle, XVIII, 43 (§144), Ier siècle apr. J.-C. : « Medica externa etiam Graeciae est, ut a Medis advecta per bella Persarum, quae Darius intulit ».
The passage verified in the Latin text (primary source). The 'Median' origin reflects ancient geography and the etymology of the name, not the real cradle of the species (Central Asia): it does not amount to botanical proof. Pliny describes a plant, not a people; the Medes are not essentialised here. No medicinal virtue is asserted here.
Key takeaways
- • Prefers full sun exposure.
- • Ideal soil: chalky, deep, well-drained.
- • Keep away from: Walnut.