You will need to thin the seedlings out at least once to prevent overcrowding and competition for air, light and nutrients; it is best to do this when the weather is mild and the soil is moist. Many plants scatter their seeds freely, often producing dense clumps of seedlings; these will also need to be thinned carefully so that the young plants may develop without competition.

Try to make sure that you keep the sturdier seedlings where possible and maintain an even spacing. To minimise disturbance to any seedlings being kept, press the soil around them with your fingers as the surplus seedlings are extracted.

You can use any seedlings you have removed to fill sparse areas caused by irregular germination or uneven sowing, or they may be transplanted for use elsewhere in the garden. In either case, choose the healthiest and strongest of the thinned seedlings, then replant them where necessary with the appropriate spacings. Water them lightly to settle their roots.