The reference study on microgreen composition, published in 2012 in the Journal of Agricultural and Food Chemistry, analysed 25 commercially available varieties. Total ascorbic acid content ranged from 20.4 to 147.0 mg per 100 g fresh weight, a sevenfold gap between the lowest and the highest. Beta-carotene ranged from 0.6 to 12.1 mg per 100 g, alpha-tocopherol from 4.9 to 87.4 mg. Saying that microgreens are rich in vitamins therefore means very little: everything depends on the species you sow. Red cabbage came top for vitamin C, cilantro for carotenoids, garnet amaranth for phylloquinone and green daikon radish for tocopherols.

That is good news for anyone growing at home, because the seed choice becomes the real lever. The rest of the method comes down to two weeks, a shallow tray and measured watering.

Microgreen or sprout: the distinction changes the risk

The two words are often used interchangeably, and they should not be. A sprout is eaten whole, seed included, after a few days in a damp, warm jar. A microgreen grows in a substrate for seven to fourteen days, then you cut the stem above the substrate, leaving seed and root behind.

That difference is not cosmetic. The conditions of jar sprouting, warmth, constant humidity and a seed in permanent contact with water, are also ideal conditions for any pathogen present on the seed. The 2011 German outbreak, documented in the New England Journal of Medicine, was linked to fenugreek sprouts contaminated with Escherichia coli O104:H4, with several thousand cases and dozens of deaths. Outbreaks linked to alfalfa sprouts continue to be reported, including a large multi-serovar outbreak in Norway in 2024.

Microgreens are not risk-free either. A 2024 study in the International Journal of Food Microbiology inoculated Salmonella, E. coli O157:H7 and Listeria monocytogenes into perlite and into seeds, then measured transfer to the edible part of twenty types of microgreens. Transferred populations ranged from 1.6 to 7.7 log CFU per gram and depended on the pathogen and the microgreen type, but not on the initial inoculation level. In other words, even low contamination of the substrate or the seed can end up on the shoot.

What that means in practice: cut above the substrate rather than pulling, work with clean equipment, avoid waterlogging, and buy seed intended for food use rather than treated garden seed. The detailed comparison with classic sprouting is covered in our article on sprouted seeds.

What you actually need, and what is optional

The useful kit comes down to four items.

A shallow container. Microgreen roots are a few centimetres long. A reused food tray, a soup plate or a seed tray all work. Two to three centimetres of substrate is enough. A deep container serves no purpose and holds water where it stagnates.

A clean substrate. Seed compost, coco coir or hemp growing mats all work. Coco coir has the advantage of being sterile as sold and of holding water without compacting. Garden soil brought in from outside carries its own flora and its own insect eggs, which makes it a poor indoor choice.

Food-grade seed. This is the item not to economise on. Garden seed may be coated with fungicide, which is legal for a seed destined to grow in open ground and unsuitable for shoots eaten raw ten days later. Seed sold for sprouting or microgreens is checked for that use.

Water and a sprayer. A reused spray bottle is enough. A fine-spouted watering can also works, provided you aim at the substrate rather than the leaves.

What is optional at the start: the grow light, bottom heat, liquid fertiliser and ready-made kits. An east, south or west facing window gives enough light for most species. A lamp becomes useful only in winter, in a dark flat, or for year-round continuous growing.

Which seeds to choose, and what they give

The table below covers the most reliable species for a first attempt, with timings observed in indoor growing at room temperature.

Species	Soaking	Harvest	Flavour
Radish	None	6 to 10 days	Sharply peppery
Red cabbage	None	8 to 12 days	Mild, slightly sweet
Broccoli	None	8 to 12 days	Mild, green
Rocket	None	7 to 12 days	Peppery
Sunflower	8 to 12 hours	8 to 12 days	Crunchy, nutty
Pea	8 to 12 hours	8 to 14 days	Sweet, crunchy
Mustard	None	6 to 10 days	Distinctly hot
Basil	None	14 to 21 days	Fragrant, slow

Radish is the best way in: it germinates fast, tolerates watering mistakes better than the others and gives a visible result in a week. Basil is the most disappointing starting point, because it takes three weeks and its seeds form a mucilage that throws people off.

Large seeds, sunflower and pea, need a soak of eight to twelve hours beforehand. Small brassica seeds do not, and they stick together if you soak them. If sunflower interests you specifically, the detailed method is in the article on sprouting sunflower seeds.

The method, step by step

Day 0, sowing. Wash the container in hot soapy water and rinse. Fill with two to three centimetres of substrate and press lightly to get a flat surface. Moisten the substrate before sowing, not after: an already damp surface stops the seeds shifting at the first watering. Spread the seed in a dense layer without overlap. For a tray of twenty by thirty centimetres, count roughly 10 to 15 g of radish or cabbage seed, 30 to 40 g for sunflower or pea, which are far larger.

Days 0 to 3, the dark phase. Cover the tray with a second inverted tray, a plate or a damp cloth. Darkness and constant humidity favour even germination, and the stems grow straighter as they reach for light. Check once a day that the substrate stays damp.

Days 3 to 5, moving into light. As soon as most seeds have germinated and the stems are lifting the cover, uncover and place near the window. Expect a rapid colour change: the shoots go from pale yellow to green in one or two days.

Days 5 to 12, growth. Water once or twice a day depending on temperature. The substrate should stay damp to the touch without a pool forming at the bottom. Turn the tray a half turn each day to counter the lean towards the light.

Harvest. Cut with scissors a centimetre above the substrate, once the cotyledons are fully open and the first true leaf is starting to appear. One cut per sowing: unlike herbs, microgreens do not regrow in any usable way.

Light, etiolation and what a too-long shoot means

A pale, thread-like, drooping microgreen has not run short of water: it has run short of light. The plant stretches its stem to reach an insufficient light source, at the expense of thickness and reserves. The result is fragile, bland and keeps badly.

Twelve to sixteen hours of light a day is right. On a windowsill in summer, natural light is ample. From November to February at our latitudes, day length and intensity fall together, and that is when an LED grow light placed twenty to thirty centimetres above the tray genuinely changes the outcome.

The second sign to watch is the lean. Shoots all leaning the same way point to light that is too lateral. Turning the tray each day straightens the batch with no extra equipment. For wider indoor growing, our article on growing herbs on a balcony covers the same exposure constraints.

Mould or roots: telling them apart

This is the question that makes people throw out the most perfectly healthy trays. Around day three or four, white fuzz often appears at the base of the stems. In most cases these are root hairs, a normal structure, and not mould.

The two are clearly distinguishable. Root hairs form a fine, even white halo centred on the root, and they disappear when humidity drops. Mould forms grey or bluish cobweb-like filaments, spreads in irregular patches over seeds and stems, and gives off a cellar smell. When in doubt, a little airflow and reduced watering over twenty-four hours will make root hairs recede, and mould will not.

The three causes of real mould are always the same: too much water, sowing too densely and no air circulation. A mouldy tray gets thrown out, substrate included, and the container is washed in hot water before reuse.

Nitrates, a point rarely mentioned

Leafy vegetables accumulate nitrates, all the more so when they grow fast, with little light and generous nitrogen. The FDHA Ordinance on maximum levels for contaminants (SR 817.022.15) sets maximum levels in Annex 1: 3500 mg of nitrate per kilo for fresh spinach, 2500 to 5000 mg depending on season and growing method for Lactuca lettuces, and up to 7000 mg for rocket harvested between 1 October and 31 March. Regulation (EU) 2023/915 sets equivalent values.

No specific maximum level is set for microgreens in these texts. That does not mean they contain none: the species concerned, rocket, spinach, cabbage, are precisely those that accumulate most. Two things limit the practical scope of the issue. First, the quantities eaten are small, around ten to twenty grams per plate, whereas the regulatory values target portions of whole vegetables. Second, growing without nitrogen fertiliser on an inert substrate such as coco coir does not supply the nitrogen source that feeds accumulation.

The useful step is therefore simple: do not fertilise a tray of microgreens. The seed holds the reserves needed for the first ten days, and adding fertiliser speeds up nothing noticeable over that period.

Storage and hygiene after harvest

Cut microgreens are fragile, very wet and handled by hand: they keep less well than a whole lettuce.

• Cut just before serving whenever you can. It is the only storage method with no loss.
• For a few days’ stock, let the shoots air-dry for a few minutes after washing, then store in an airtight container lined with kitchen paper, refrigerated. Count on three to five days.
• Wash under cold running water just before eating, without soaking. A long soak softens the stems and spreads any localised contamination through the water.
• Do not pre-wash the batch you are storing: residual water speeds up spoilage.

Washing lowers the surface microbial load without eliminating it. For people who are immunocompromised, pregnant or elderly, quick cooking remains the cautious option, exactly as for sprouts. General principles for keeping fresh produce are developed in the article on storing fruit, vegetables and legumes.

What microgreens bring to a plate, without overstating it

Back to the 2012 figures. Red cabbage microgreens sit among the richest in ascorbic acid in the sample, with levels near the top of the 147.0 mg per 100 g range. But a realistic portion of microgreens weighs ten to twenty grams, not a hundred. Actual intake therefore comes to a few milligrams up to around twenty milligrams of vitamin C, against a nutrient reference value of 80 mg.

That is still useful, mainly because it arrives raw and fresh, with no transport or long storage. It does not make microgreens a primary source of anything. They replace neither vegetables in quantity, nor legumes for protein, covered in the plant protein guide, nor a reliable source of vitamin B12, detailed in the B12 guide.

WHO recommends at least 400 g of fruit and vegetables a day for people over ten. A handful of microgreens contributes only marginally by weight. Their real value lies elsewhere: they bring flavour, texture and colour for minimal effort, and they make simple dishes more appetising. A squash soup, a hummus or a plate of lentils gains more from being livened up than from being enriched.

Uses that work

Microgreens do not take heat well. They lose their texture within seconds in a pan and turn a dull green. So they go on at the end, never into the cooking.

• As a finish on a hot dish. Soup, curry, gratin, risotto: scatter at serving time, on the plate rather than in the pan.
• In a sandwich or wrap. They beat a lettuce leaf, with more flavour and without the water that sogs the bread.
• In a mixed salad. Blended into a more neutral base rather than alone: a whole plate of mustard microgreens is inedible.
• On toast with soft cheese or hummus. The fat carries the peppery notes of radish and rocket.
• In an omelette, after cooking. Laid on the folded omelette, not mixed into the eggs.

The common principle is pairing a fatty or neutral base with a strongly flavoured shoot. Pea and sunflower microgreens, milder and crunchier, are the only ones that work in quantity in a salad. To build a full meal around them, the article on a complete satisfying meal salad gives the proportions.

Common mistakes

• Sowing too densely. Overlapping seeds do not all germinate, air does not circulate and mould follows. A tight layer without overlap is the right density.
• Watering from above with a strong jet. Seeds shift, young stems flatten and water sits on the leaves. Spray, or water from the bottom of the tray.
• Leaving the tray covered too long. Past four or five days, darkness prolongs etiolation rather than helping.
• Using garden seed. A fungicide coating is designed for a plant that will grow for months, not for a shoot eaten raw in ten days.
• Mistaking root hairs for mould. Even white fuzz around the roots is normal.
• Fertilising. Pointless over ten days, and the added nitrogen encourages nitrate accumulation.
• Waiting for a second cut. Microgreens do not regrow usefully after harvest.
• Washing the whole batch then storing it. Residual water speeds up spoilage; wash just before eating.

Adapting to different situations

Dark or north-facing kitchen. Favour radish, pea and sunflower, which tolerate weak light better, and accept longer stems. An LED lamp pays off if you grow year-round.

Hot flat in summer. Above twenty-five degrees, mould advances fast. Water less, sow less densely and harvest a day or two earlier.

Pregnancy, older age, weakened immunity. The same precautions as for sprouts apply: quick cooking remains the cautious option, and raw microgreens, shop-bought or home-grown, undergo no microbial reduction step.

Households with children. Growing is a good teaching tool, and radish delivers a result in a week, which matches the available patience. Dry seeds stay out of reach of the youngest.

Tight budget. Radish, mustard and sunflower seed bought as culinary packets, in the food aisle, costs far less than packets labelled for microgreens, provided they are intended for eating. Reused food trays replace seed trays.

Continuous growing. Sow a new tray every five to seven days rather than one large tray at once. Production spreads out and nothing is wasted.

What these figures do not tell you

The 2012 study covers 25 commercial varieties analysed at one specific stage. Your own shoots, sown on a different substrate, under different light and cut on a different day, will have different levels. These numbers give orders of magnitude and a ranking between species, not a value for your tray.

The 2024 pathogen transfer study involves deliberate inoculation under controlled conditions, which answers the question of transfer but not that of how often commercial seed is actually contaminated. The nitrate maximum levels quoted concern whole vegetables and do not transpose directly to a ten-gram portion of microgreens. Finally, none of the timings here is a guarantee: the temperature, humidity and light in your home will shift them by one to three days.

Frequently asked questions

Are microgreens more nutritious than mature vegetables? Weight for weight, the 2012 study found higher nutrient densities in the cotyledons than in the corresponding mature leaves in the USDA database. But you eat ten to twenty grams against a hundred to two hundred grams of vegetable, which largely reverses the arithmetic at plate level.

Can I reuse the substrate? Not for another food crop: it is spent and colonised. It goes on the compost, or as a mulch at the base of houseplants.

Should seeds be rinsed before sowing? For small brassica seeds, no, they stick together. For large soaked seeds, yes, a rinse after soaking removes the soaking water and the debris.

How many times a day should I water? Once or twice, depending on temperature and substrate. The test is touch: damp, never sodden, never dry on the surface.

My shoots collapsed all at once, why? Two possible causes. Too much water at the collar, rotting the base, or advanced etiolation where the stems can no longer hold themselves up. Either way the current batch is lost; the next one needs less water and more light.

Are tomato or aubergine microgreens edible? No. Nightshades produce alkaloids in their green parts, and their seedlings are not eaten as microgreens. Stick to brassicas, legumes, cucurbits, herbs and oilseeds.

Can you grow without substrate, on water alone? Hemp or jute growing mats work for mucilaginous seeds and large seeds. Growth is slightly slower and the harvest cleaner, with no compost particles.

How long before sowing again in the same tray? Immediately, provided you wash it in hot soapy water and dry it. The container is not the limiting factor, the substrate is.

Sources

• FDHA Ordinance on maximum levels for contaminants, SR 817.022.15, Annex 1 on nitrates: official text
• Regulation (EU) 2023/915 on maximum levels for certain contaminants in food: text
• Xiao Z. et al., Assessment of vitamin and carotenoid concentrations of emerging food products: edible microgreens, Journal of Agricultural and Food Chemistry, 2012: PMID 22812633
• Transfer of Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes from contaminated soilless substrate and seeds to microgreens, International Journal of Food Microbiology, 2024: PMID 38325258
• Understanding food safety on sprouts and microgreens: contamination routes, outbreaks and challenges, Food Research International, 2025: PMID 40467198
• German outbreak of Escherichia coli O104:H4 associated with sprouts, New England Journal of Medicine, 2011: PMID 22029753
• A large outbreak of multiple Salmonella serovars linked to alfalfa sprouts in Norway, Infection, 2025: PMID 40394450
• World Health Organization, E. coli fact sheet: official page
• World Health Organization, healthy diet fact sheet: Healthy diet
• Swiss dietary recommendations for adults: official page
• Swiss Food Composition Database: naehrwertdaten.ch

A tray of radish on a windowsill takes ten minutes to set up and seven days to wait. It is one of the few growing tasks that delivers on the first attempt. If the growing habit takes hold, the article on balcony permaculture basics picks it up at a larger scale, and seed swapping with neighbours covers where to find varieties worth trying.