Fill your tray or container with John Innes seed and potting mix to within a half-inch of the rim, tapping them on the side to help settle the mix. Top up as necessary. If using pots or cells, place a few seeds into each one, and then give a light covering of compost, firming it down gently over the seeds. If you are using a seed tray then give a light and even sprinkling of seeds across the whole tray at approximately 5 seeds per square inch. Once done, give a light covering of compost and water in. Label with the variety and date of sowing, and place in into a covered propagator making sure the vents are fully open. Now leave in a bright, warm room, out of direct sunlight. The more light they can receive the better the germination. Once the seedlings reach about 2 inches in height, thin out and discard any that look weak. Those in the seed tray can be ‘pricked’ out and potted on into a standard potting mix. Those already in pots can be hardened off in preparation for moving outside.
If your seedlings were grown under glass then they will also need to harden off before going outdoors. Place them into a cold-frame but keep the lid closed for a couple of weeks. Afterwards the lid can be opened on dry frost free days but remember to shut it again at night. After a further week or so, or when frosts are no longer expected, leave the lid open day and night for a week before planting outside.
To harden off seedlings that have been grown indoors in a heated room, moved them to a bright unheated room, then leave them there for a couple of weeks before either putting them into a cold frame, or for leaving them outside during the day. Never leave them out over night, and keep them in if there are strong cold winds of if temperatures drop below 6 degree Celsius. Keep this up for a week and if there is no immediate threat of further frosts they can be planted outside.
Pick the baby leaves as required and plants will re-grow for a further 3-4 cuts. For mature plants, allow them to develop fully before harvesting which – depending on the weather - can be as early as June.