Mustard
Sinapis alba
Botanical family: Brassicaceae
White mustard (Sinapis alba) and brown mustard (Brassica juncea) are very fast-growing Brassicaceae, grown as green manures.
Full sun
Light, any well-drained soil
Moderate, fast germination if the soil stays cool
Annual, killed by frost
An annual killed by frost in your zone
Role in permaculture
Sown as a catch crop, it smothers weeds and structures the soil surface, then enriches it with organic matter once shredded and buried. Buried at full flowering, it can also curb some soil pests through biofumigation, brown mustard more so than white.
Insects attracted or useful
Known pests & diseases
Pests and diseases that commonly affect this plant, tap to learn how to recognise and manage them.
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…”.
A fast-growing cover with dense roots that pump up the mineral nitrogen left at the surface and immobilise it in their biomass, curbing leaching to the water table over winter. It's a nitrogen SINK, not a source, the opposite of a legume. A worldwide meta-analysis: cover crops reduce nitrate leaching by about 70% on average versus bare soil, and the crucifers (including mustard) are among the most effective, precisely because they don't fix nitrogen. The effect is clearer on coarse-textured soils.
scientific study
- · Nouri A., Lukas S., Singh S. et al. (2022), Global Change Biology 28:4736-4749, DOI 10.1111/gcb.16269
Chopped then buried, the mustard releases isothiocyanates, the sulphur compounds of its pungency, reputed to sanitise the soil. The chemical mechanism is well described, but the field effectiveness is irregular and not quantifiable: the same study obtains a significant reduction of one nematode in one trial and no effect in the next. Specialists recommend biofumigation only as a support to integrated management, never as a standalone solution.
scientific study
- · Ngala B.M. et al. (2015), Pest Management Science 71(5):759-769, DOI 10.1002/ps.3849
- · Tikkisetty P.P. et al. (2025), Plants 14(8):1200, DOI 10.3390/plants14081200
A mechanism distinct from biofumigation: certain RESISTANT cultivars of white mustard cause the nematode's larvae to hatch through their root exudates, without letting them reproduce, the population declines. Everything hinges on the cultivar: a resistant cultivar makes the population crash, a poorly chosen cultivar can instead multiply it. To be reserved therefore for certified resistant varieties, and for this precise nematode species.
scientific study
- · Wright A.J. et al. (2019), Pest Management Science 75(2):438-443, DOI 10.1002/ps.5134
- · Smith H.J., Gray F.A., Koch D.W. (2004), Journal of Nematology 36(2):123-130 (PMC2620762)
Seasons & availability
A very fast-growing green manure: sown in spring, from March to May, and above all from late August to September, the cover growing on until the frosts before being chopped and dug in.
Available: April, May, June, July, August, September, October, November, December.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- RHS, « Green manures » (rhs.org.uk/soil-composts-mulches/green-manures)
- La Ferme de Sainte Marthe, « Réussir la culture de la moutarde blanche » (fermedesaintemarthe.com/en/blogs/comment-reussir-la-culture-de/reussir-la-culture-de-la-moutarde-blanche)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
The mustard plaster can burn the skin: keep external use brief and monitored. Like all brassicas, an excess of raw crucifers may interfere with the thyroid in sensitive people.
Family behaviour: Brassicaceae
In general, Brassicaceae produce glucosinolates, sulphur compounds with a mild biocidal effect on the soil (a biofumigant effect, sometimes sought between two sensitive crops). Members of the cabbage and mustard family, they are prone to the cabbage white and clubroot.
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, reporting a judgement attributed to Pythagoras · Rome, Natural History, 77 AD
In his Natural History, Pliny the Elder reports that Pythagoras ranked mustard (sinapi) first among the plants whose force 'rises' upward, for nothing, he writes, penetrates more sharply into the nostrils and the brain. Pliny then ascribes to it a long series of uses: bites of snakes and scorpions, chest complaints, sneezing to clear the head, stomach disorders. What the text attests is the place of mustard in the Roman pharmacopoeia, where its very pungency was read as a virtue; the judgement about the 'force that rises', for its part, belongs to ancient physiology and not to an observation one could take up today.
Pline l'Ancien, Histoire naturelle, livre XX, chapitre 87 (« sinapi »), 77 apr. J.-C.
An attested fact: Pliny's text does say this (the Latin formula verified on LacusCurtius). But it's an ancient medicinal use, on no account to be transposed into a modern health indication: no curative virtue is presented here as a fact, and the idea of a 'force that rises' belongs to the ancient reading of the plant, not to current pharmacology.
Jesus of Nazareth, in the tradition of the synoptic Gospels · Galilee, 1st century; the Greek texts that report it were written around 70–90 AD
The parable of the mustard seed compares the kingdom of heaven to a grain of mustard, 'the smallest of all seeds', which nonetheless becomes a shrub where the birds come to nest. The image rests on the contrast between the tiny seed and the developed plant. What is attested is the Gospel text itself, present in the three synoptic Gospels; the phrase 'the smallest of all seeds' is a proverbial hyperbole of the discourse, and not an exact botanical datum.
Évangile selon Matthieu 13, 31-32 (parallèles : Marc 4, 30-32 ; Luc 13, 18-19), textes rédigés vers 70-90 apr. J.-C.
The attested fact is the Gospel text. The phrase 'the smallest of all seeds' belongs to spoken imagery, not to a measurement: it is presented here as a cultural metaphor and not as a botanical fact. No medicinal virtue or health claim is associated with it.
Keep in mind
Warning: mustard is itself a Brassicaceae, therefore a host of clubroot (Plasmodiophora brassicae) and flea beetle. Not to be sown as a cover on a plot where cabbages are planned soon, nor conversely after cabbages. The biofumigant effect requires shredding at full flowering and immediate burial.
A note on rigour: many companion pairings are gardening folklore; this note sums up what the sources say, where there are any.
Key takeaways
- • Prefers full sun exposure.
- • Ideal soil: light, any well-drained soil.