How to Grow Microgreens Indoors (UK Beginner's Guide)

Microgreens are young vegetable and herb seedlings, harvested just after the seed leaves (the cotyledons) open and the first true leaves begin to show, usually when the plants are 3-8 cm tall. They sit between a sprout, which is eaten whole after a few days including the root, and a baby leaf, which is grown on for several weeks. You snip microgreens off at soil level and eat the tender stems and leaves raw.

They earn their windowsill space for more than novelty. A widely cited study from the University of Maryland found that many microgreens carry higher concentrations of vitamins and carotenoids than the same plants grown to maturity, in some cases around five times more (University of Maryland, 2012). For a plain-English primer on what does and does not count as a microgreen, the Wikipedia entry on microgreens is a solid starting point.

The kit list is short, and most of it you probably already own:

• A shallow tray with drainage. A seed tray works, but a clean takeaway container or fruit punnet with a few holes poked in the base is fine.
• A growing medium. Peat-free multipurpose compost or coir (a coconut-fibre growing medium) both work well. You only need a thin 2-3 cm layer.
• Seed. You can buy dedicated microgreen or sprouting seed, or use ordinary vegetable seed bought in bulk. Because you sow so densely, buying larger packets keeps the cost down.
• A spray bottle for gentle, even watering.
• Light. A bright windowsill for most of the year, or a small LED grow light for dim rooms and midwinter.

No heat mat, no propagator, and no fancy equipment are required to get a first tray going.

Start with fast, forgiving varieties before you branch out:

• Radish is the classic first crop: it germinates in a day or two, grows vigorously, and is ready in about a week with a pleasant peppery bite.
• Pea shoots are sweet and crunchy, ready in 10-14 days, and the one common microgreen that reliably gives a second cut.
• Broccoli and kale are mild, nutritious brassicas that grow evenly in 10-14 days.
• Sunflower gives thick, nutty shoots; soak the large seeds overnight first.
• Mustard and cress are among the fastest of all and great for children to grow.

Leave the tricky ones until you have a few trays behind you. Mucilaginous seeds such as chia, basil and rocket form a jelly-like coating when wet and need a firmer surface and misting rather than watering, so they are easier once you know the rhythm.

Usually not. The punnets of "salad cress" sold in UK supermarkets are mostly salad rape (Brassica napus, a mild leafy relative of oilseed rape) grown alongside a smaller share of true cress, and the ingredient labels say so. Sainsbury's own British salad cress, for example, lists a mix of roughly 70% rape to 30% cress. Kings Seeds, an Essex seed house, states plainly that most supermarket cress is salad rape (Kings Seeds).

That matters at home for two reasons. First, if the mild flavour of shop cress is what you like, sow salad rape rather than true cress (Lepidium sativum), which is sharper and more peppery. Second, the classic school-windowsill method still works: cress, mustard and salad rape all grow on damp kitchen paper or a flannel with no compost at all, which makes them the cheapest possible first experiment. Sow mustard three or four days after the cress if you want them ready together, because cress is the slower of the two.

Knowing what normal looks like stops you panicking at the wrong moment. Here is the usual progress of a tray of radish, the easiest first crop, sown on a kitchen windowsill at ordinary indoor temperatures of 18-21°C:

Pea shoots and sunflower follow the same pattern a few days slower. Cool rooms slow everything: a tray on a sill that drops to 12-14°C overnight in January can take half as long again, which is normal rather than a sign of failure.

Less than you might think. A bright windowsill is usually enough, even a north-facing one, because you harvest microgreens long before they need strong light to flower or fruit. South- or west-facing sills give faster, sturdier growth.

In a dim room or through the darkest UK winter weeks, a small LED grow light run for 12-16 hours a day stops shoots going pale and leggy. If you want to understand why the colour of that light matters, our guide to grow-light spectrum explains it simply. Microgreens are also one of the best crops for a genuinely low-light spot, which is why they feature in our north-facing balcony planting list.

The UK is far enough north that the season changes the picture more than any guide written for sunnier climates admits. On the shortest day, London gets 7 hours 49 minutes of daylight according to the Royal Observatory Greenwich, and Edinburgh under seven hours, against more than 16 hours in midsummer. Winter light is also weaker and lower in the sky, so a sill that grows sturdy trays in May produces leggy, pale ones in December.

Scotland and the north of England have a longer dim season than the south coast, so growers there gain more from a grow light. Peas and radish are the most tolerant midwinter crops because the large seed carries enough stored energy to do most of the work.

Little and often is the rule. During the blackout period, mist to keep the surface damp. Once the tray is uncovered, water into its base every day or two so the compost stays evenly moist.

The biggest beginner mistake is overwatering, which invites mould and damping off (a fungal collapse of seedlings at soil level). Watering from below, giving the tray some airflow, and not sowing quite so thickly next time prevent almost all of it.

Sow little and often rather than one big tray. Because most microgreens give a single cut, a supply depends on having trays at different stages, the same principle as succession sowing outdoors.

A workable rotation for a two-person household is two small trays (a half-size seed tray or a large takeaway container each) sown every five days:

• Day 1: sow one tray of radish and one of pea shoots.
• Day 5: sow a tray of broccoli or kale and a tray of mustard or cress.
• Day 8-10: harvest the radish; the first peas follow a few days later.
• Day 10: sow the next pair, and keep going on the same five-day beat.

At any moment you have one tray in the dark, one or two greening up and one ready to cut. That fits on a single windowsill, roughly 60-80 cm of sill space. In winter, stretch the interval to a week, because trays take longer to reach harvest. Our winter indoor growing guide shows how microgreens slot alongside windowsill herbs through the darkest months.

Keep a simple note of sowing dates and how each tray turned out. After three or four rounds you will know your own sill's timings far better than any general guide can tell you.

Most microgreens are ready 7 to 21 days after sowing, once the cotyledons have fully opened and the first true leaves are showing. Snip a handful at a time just above the compost with clean scissors, rinse, and eat within a few days for the best texture and flavour.

Despite the name, most varieties are not cut-and-come-again: you take one main harvest, then compost the spent roots and re-sow. Pea shoots are the reliable exception. Leave 2-3 cm of stem and many will push out a lighter second cut before they tire.

Almost every beginner asks this, usually around day two or three. Root hairs are fine, even, bright white fuzz along the roots of every seedling, most visible in dry air, and they collapse and vanish for a moment when you mist them. Mould is greyish, cobwebby and patchy, spreads across the compost surface and up the stems, smells musty, and does not disappear when wet.

A mouldy tray is not worth rescuing. Compost it, wash the tray in hot soapy water, and start again with a lighter sowing.

Yes, with sensible hygiene, and the risk is lower than with sprouts. Sprouts are germinated in warm, wet jars and eaten whole, seed and root included, which suits bacteria; the large 2011 E. coli outbreak in Germany was traced to sprouted fenugreek seed (2011 Germany E. coli outbreak). Microgreens grow in compost in open air and you cut them above the soil, leaving seed and roots behind.

Four habits cover most of the risk:

• Buy seed sold for sprouting or microgreens. Some garden vegetable seed is coated with a fungicide treatment, usually dyed and labelled as treated on the packet. Never sow treated seed for eating.
• Use fresh compost or coir each time and a tray washed in hot soapy water.
• Cut cleanly above the soil line so no compost comes away with the stems, then rinse.
• Wash your hands before handling seed and before harvesting.

Anyone pregnant, elderly or with a weakened immune system should follow their own clinical advice on raw sprouted foods, which in the NHS is usually to cook them.

For most growers, yes, and by a wide margin once you are past the first sowing. A shop-bought punnet holds only a small handful and is priced at a premium per gram. A single seed packet, sown densely, fills a whole tray, and buying sprouting seed in bulk brings the cost per tray down further still.

The only ongoing costs are seed and a little compost. A windowsill needs no electricity at all, and even a small grow light draws just a few watts. Set against the price of the punnets you would otherwise buy, a tray typically pays for itself within its first couple of cuts.

Cut only what you will eat in the next few days; an uncut tray is the best store there is. Harvested microgreens keep three to five days in the fridge if you rinse them, dry them gently on a clean tea towel, and store them in a lidded box lined with kitchen paper. Wet leaves go slimy fast, so drying matters more than anything else.

Buy a packet of radish and a packet of pea shoots sold for microgreens, fill two takeaway containers with 2-3 cm of peat-free compost, sow thickly, cover for three days, then put them on your brightest sill and water from below. You will be cutting radish within about a week. Once that works, add a second pair of trays five days later and you have the start of a year-round rotation. From November to February, add a small grow light or lean on peas and radish.