Essentially, you're harvesting plants at a tender stage to be added to sandwiches and salads. Many seeds can be grown as microgreens, such as salad and lettuce leaves, soft herbs like parsley, brassica (cabbage, broccoli etc) and some legumes, like peas.
They all produce tasty leaves to be harvested after two to four weeks, and sowing microgreens successionally every week can give an endless supply.
To start, get set up with some compost (multipurpose or a seed sowing compost), some suitable seeds, a tray and a waterer with a fine rose. Other useful resources could be a sieve, labels and levelling board. Fill up the tray (a shallow reusable plastic food tray could work well, for micro greens you only need around 3-6cm soil depth) that has been cleaned using hot soapy water and well rinsed prior to use. Fill to the top of the tray and then gently firm so the soil is around ½cm from the top.
Add the seeds, by thinly scattering them evenly across the compost around one to three seeds per centimetre squared is enough. Check the seed packet to see what depth the seeds you are using need to be sown at, some like peas and brassicas will need to be planted below the surface.
Sift compost over the top using a sieve or, away from the tray, rub the compost between your fingers and remove larger pieces so you can add fine textured compost over the seeds. A seed contains a store of energy and so compost that's too compact or too large may stop them reaching the light.
Water with a fine rose watering can, or as in the photos we have, use a bottle top watering rose which you can find online; they make excellent waterers for tabletop gardening.
Label the tray if you are sowing lots of seeds or will be successional cropping microgreens. Labelling is very important in horticulture but for home gardening less so and if you are only sowing a few things then you might remember what is in each tray. The most important thing to write on the label is the date, so you know that if four weeks have passed the seeds in that tray are not going to germinate unless it is a very specific plant that takes a long time to begin growing.
Now take the seed tray to where it will germinate, a windowsill is good. You are generally looking for a space with good light but not direct sun and away from draughts. Check on them every couple of days and make sure the compost is still moist.
Wait a couple of weeks, sometimes sooner, and the seeds will germinate. Then a week or two more will see them develop their true leaves and it is at this point they can be harvested.
To harvest, use scissors to cut just above the compost level. Some may then grow another set of true leaves for a second harvest. A third is less likely and may start to lose taste and nutrition, so we would recommend only two.