Microgreens on the windowsill: a crop in 7–10 days, no soil

Microgreens are the seedlings of vegetables and herbs, cut at the seed-leaf stage 7–14 days after sowing. You can grow radish and garden cress without soil, on damp paper or in a sprouting tray, on an ordinary windowsill. In Estonia there is little light in late autumn and winter, so the shoots will stretch and grow more slowly, but you will still get a crop.

What you will need

• A container: a shallow tray or box, or a sprouter with a mesh insert and a drip tray. Mesh is easier than paper: the roots reach down into the water and the stems stay dry.
• A growing surface: 3–4 layers of kitchen paper, or a linen or jute sprouting mat. Cotton wool soon turns sour, so it is best avoided.
• A spray bottle and clean drinking water.
• Seed sold for sprouting. Seed meant for the vegetable bed is often treated with fungicide. That is fine in the garden, but you must not eat shoots grown from it. The packet should say it is for sprouting or microgreens.

How thickly to sow

The most common mistake is sowing too thickly. The seeds should lie in a single layer, almost touching, never heaped. As a guide for a 10×20 cm tray:

• Radish: 6–7 g, about two teaspoons
• Garden cress, mustard, rocket: 2–3 g, a scant teaspoon
• Sunflower: 10–15 g
• Peas: 20–25 g, about two tablespoons

Soak peas for 6–12 hours and sunflower for 8–12 hours in cool water. Small seeds need no soaking. Cress, rocket and mustard give off a gel in water and clump together, so sow them dry onto a well-soaked surface.

Day by day

• Day 1. Wet the surface so it is soaked but has no puddles. Scatter the seed, mist it and cover it with a lid or a second tray. Seeds germinate best at 18–24 °C.
• Days 2–3. Keep them in the dark, checking and misting once or twice a day. Radish and cress need only 1–2 days under cover; peas and sunflower need about three.
• Days 3–4. Once the shoots are 1–2 cm tall, take the cover off and move the tray to your brightest window. From now on, water into the drip tray rather than over the leaves.
• Days 7–14. Cut when the seed leaves have opened and turned green and the shoots are 5–10 cm tall. Snip with scissors just above the surface, leaving the roots and seed husks behind.

Timings by crop

These are the times from sowing to cutting at room temperature. On a winter windowsill, add 2–4 days.

• Garden cress: 7–10 days, with a slight bite
• Radish: 7–10 days, as hot as a young radish. Up in 1–2 days, so it is the best choice for a first try
• Mustard, rocket: 7–10 days, spicy and peppery
• Sunflower: 9–12 days, crunchy and nutty. Cut before the true leaves appear, or the stems turn bitter
• Peas: 10–14 days, sweet, tasting of fresh garden peas
• Coriander: 3–4 weeks. This is the slowest crop, and it does poorly on paper. Sow it into a thin layer of compost or coir instead

Light in an Estonian winter

In December, Tallinn gets only about six hours of daylight. Seeds need no light to germinate, but once the cover is off there may not be enough: the shoots stretch, turn pale and flop over. From October to February, keep the tray on a south- or west-facing window. If the shoots start to lean, add a basic LED grow light or a daylight tube 15–30 cm above them for 12–16 hours a day. From March a window is usually enough.

Mould or root hairs?

On day 2 or 3, radish, mustard and other brassicas grow a white fuzz on their roots. These are root hairs, which the plant uses to take up water. They are easy to tell apart from mould:

• Root hairs are bright white and even, grow only on the roots, and collapse when misted so that you can hardly see them.
• Mould looks like cobweb that spreads from the roots onto the seeds, stems and growing surface. It can be grey or greenish, smells musty and does not go away when wet.
• Jelly around cress and mustard seed on the first day is the natural seed coating, not mould.

Mould comes from standing water, sowing too thickly, heat and stale air. If a patch of it has spread, throw out the whole tray, wash the container in hot soapy water and sow again a little more thinly.

Hygiene and safety

Seedlings grow in warmth and moisture, and bacteria multiply quickly in those same conditions. Microgreens cut above the surface are safer than sprouts, which are eaten whole with the seed and root, but a few simple rules still apply:

• Wash the tray and mesh in hot water before every sowing, and use drinking water.
• If you sprout seeds in a jar, rinse them under running water at least twice a day, more often when it is warm, and drain them well.
• Do not eat shoots that smell sour or look slimy or mouldy.
• Rinse the crop before eating, dry it and keep it in a closed box in the fridge at 1–5 °C. It is best eaten within 3–5 days.
• Raw sprouts are not recommended for pregnant women, small children, older people or anyone with a weakened immune system. For them, add the greens to hot dishes instead.

What not to do

• Do not sow treated seed meant for the garden: shoots grown from it must not be eaten.
• Do not sow two or three layers deep: the bottom seeds rot and mould follows.
• Do not let water stand in the bottom, and do not keep the tray covered once the seeds are up.
• Do not soak small gel-forming seeds: cress, rocket and mustard will clump into a lump.
• Do not put the tray on a hot radiator: the surface dries out and the air becomes stuffy.

Frequently asked questions

Do I need a grow light?

Not for germination. From October to February, shoots on a north-facing or shaded window will stretch. A basic LED light for 12–16 hours a day will help.

Can I get a second cut?

Peas sometimes regrow if you cut above the lowest leaf, but the second crop is weaker. Radish, cress and sunflower do not regrow, so it is easier to sow again.

Do microgreens need fertiliser?

No. The seed holds all the food the plant needs for its first two weeks. All it needs is clean water.

How long do cut microgreens keep?

3–5 days in a closed box in the fridge. Cut them dry and wash them just before eating.

From our catalogue

You will find every crop and sprouting kit in the seeds for sprouting microgreens section.