Sweet clover (melilot)
Melilotus officinalis
Botanical family: Fabaceae
Melilotus officinalis, with its long racemes of small fragrant yellow flowers, grows spontaneously along paths as well as as a cultivated green manure. Traditionally used as an infusion for its relaxing properties on venous circulation, it remains above all, in the garden, an ally of the soil and of pollinators.
Full sun
Chalky, dry to medium
Low, a hardy and undemanding plant
Hardy biennial
Overwinters in your zone
Role in permaculture
A biennial Fabaceae with a deep taproot, melilot captures atmospheric nitrogen and is reputed to improve the structure of compact chalky soils. Its fragrant yellow flowering makes it one of the most renowned nectar plants, sought after by beekeepers for melilot honey.
Good companions
Traditional companion planting (benefit not demonstrated)
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…”.
The sweet clover fixes atmospheric nitrogen, and in a field trial almost all of its nitrogen came from this fixation, even in salty soil. On the other hand, the amount actually returned to the soil (kg of nitrogen per hectare) is not measured in this work: the benefit as a green manure depends on the biomass produced, which was not converted into returned nitrogen.
scientific study
- · Bruning B. et al. (2015), AoB Plants 7:plv010, DOI 10.1093/aobpla/plv010
- · Huang R., Snedden W.A., diCenzo G.C. (2022), Plant Direct 6(6):e408, DOI 10.1002/pld3.408
The sweet clover contains coumarin, the molecule of its cut-hay smell, an aqueous extract of which slows weed germination in the laboratory. But the effect is only demonstrated in a bioassay, not under real soil conditions. To be seen as a reason for caution with neighbouring seedlings rather than as a guaranteed weedkilling asset.
scientific study
- · Wu C.C. et al. (2016), International Journal of Agriculture and Biology 18(1):168-175
A reference honey plant: its long, nectar-rich flowering feeds honeybees and wild bees for several weeks. The honey-plant status is widely recognised; no figure (honey yield, sugar per flower) is put forward here, for want of verification at a primary source; the interest is solid qualitatively.
reference work
- · USDA Forest Service, Fire Effects Information System, Melilotus (species profile)
Its deep taproot (up to ~1.5 m), among the deepest of the cover legumes, explores the subsoil and can help loosen a compacted profile over its two years of life. The extent of the decompaction depends on the soil and is not quantified here, but the root depth itself is well documented.
reference work
- · USDA Forest Service, Fire Effects Information System, Melilotus (Nebraska root profiles)
Seasons & availability
A biennial green manure: sown from spring to the end of summer, its yellow, nectar-rich flowering runs from June to September, then it is cut and dug in to feed the soil.
Available: March, April, May, June, July, August, September, October.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Plants For A Future, « Melilotus officinalis » (pfaf.org/user/Plant.aspx?LatinName=Melilotus+officinalis)
- Tela Botanica, « Melilotus officinalis (L.) Lam. » (tela-botanica.org/bdtfx-nn-41839-description)
- Gerbeaud, « Mélilot jaune ou blanc » (gerbeaud.com/jardin/jardinage_naturel/melilot-jaune-blanc,2366.html)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Rich in coumarin: if poorly dried, it produces dicoumarol, a powerful anticoagulant, toxic to livestock (historically the cause of fatal haemorrhages in cattle fed on spoiled hay, and later of the discovery of warfarin). This well-documented risk concerns fodder use, not its cultivation as a green manure in the garden. Not advised alongside anticoagulant treatment or before surgery.
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.
Understanding families means learning one rule per family rather than every pairing one by one. Learn more →
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 · Italy (Campania), 1st century AD
In his Natural History, Pliny the Elder names sweet clover sertula Campana, the 'little garland of Campania', and holds the most esteemed to be that which grows in Campania. Its Greek name, melilotos ('honey lotus'), evokes its honeyed smell. The word sertula ('garland') and the subject of book XXI, devoted to garland flowers, likely tie the plant to the making of fragrant garlands. This precise use, however, remains inferred from the context, and not asserted as such by Pliny: it should not be over-interpreted.
Pline l'Ancien, Histoire naturelle, livre XXI (Ier siècle apr. J.-C.) : « melilotum, quod sertulam Campanam vocamus. est enim in Campania Italiae laudatissima ».
The Latin name and the Campanian reputation are attested by the Latin text itself, a primary source. The use in garlands, on the other hand, is a reconstruction from the name sertula and the theme of book XXI: plausible, but not explicit. The chapter numbering varies with editions; it's the Latin quotation that is authoritative. No medicinal use is put forward here, and one refrains from essentialising Roman culture from a single notice.
Key takeaways
- • Prefers full sun exposure.
- • Ideal soil: chalky, dry to medium.
- • Classic companion: Rye.