Using a coarse wire-mesh sieve, sift a very fine (1/8-inch) layer of dry potting mix over the seeds. Set the container onto a drip tray and then carefully water the seeds in with a gentle shower from a watering can. Place the tray on a sunny, south-facing windowsill or under grow lights. Expect the seeds to germinate in 3 to 7 days.
Keep the soil consistently moist. Prevent soggy soil by pouring off any excess water that collects in the drip tray after watering. To harvest, snip the microgreens right above the soil line when their first true leaves unfurl (about 7 to 14 days after germination, depending on the green). The microgreens are nutrient-dense and make a healthy addition to salads and sandwiches.
Learn more about growing Salad Greens.