Some seeds are sown in trays or pots very close together and once they have germinated, the individual small seedlings need to be 'pricked out' and moved to give them more 'growing space' - normally the plants will again be transferred when they have grown further to another pot or into the garden.
Pricking out needs to be done when the seedlings have reached the 'true' leaf stage, this is normally the second pair of leaves (the first pair being the 'seed leaves').
Before starting to move the seedlings, their new 'home' must be prepared - this can be an ordinary seed-tray (ideally 7.5cm (3 inches) deep), a cellular seed-tray or individual small pots (typically 6 to 7.5cm (2½ to 3 inches) diameter) - peat pots have the advantage that these can later be planted into the garden soil without again disturbing the plant, peat-alternative pots are also available. Whichever type of container is used, it should be filled with good potting compost and firmed down.
Before transplanting the seedlings, make sure that the compost in both the original container and the new container is moist - water the containers and allow to drain if necessary.
In all probability there will be more seedlings than are required, so only prick out and move the best, healthy seedling - discard any weak looking seedling, they are unlikely to recover after transplanting.
Remove one seedlings at a time from the original container by carefully loosening the compost under the seedling using a small dibber or pencil, the seedling should be lifted out by holding the seed leaves (the lower pair) - avoid holding them by the stem or roots.
The replanted seedlings normally need to be spaced about 3.7cm (1½ inches) in a new seed-tray (cellular seed-trays take one seedling per cell, pots need one seedling each), so use a small dibber or pencil make a hole in the new compost just large enough - width and depth - to take the roots. Hold the seedling so that the seed leaves are about level with the top of the compost and fill in the hole around the roots and firm down - take care that there are no air pockets left under the seedling.
When all the required seedlings have been transplanted, water the containers using a fine watering rose.
Shade the transplanted seedlings from direct sunlight (use a single sheet of newspaper) for 3 or 4 days to give them a chance to become established in their new containers.
Water and grow on as necessary.