Aftercare of seedlings

Seeds sown in pots or trays

Ensure that the compost is not allowed to dry out, otherwise the seedlings will die.

When the seedlings have two true leaves you can also start to feed them with an inorganic liquid feed (this is particularly important for seedlings growing in rockwool) or slow release fertiliser added into the potting compost when potting on.

Once the seedlings are large enough to handle (the timescales will vary greatly depending on the type of plant) water the container in advance (allowing it time to drain), tap it to loosen the soil and then remove the seedlings from it carefully so that the roots are not damaged (this is easiest done with a dibber or widger). If grown in a pot, you can gently tip the whole contents of the pot onto the work surface and tease out the seedlings’ roots. Always handle seedlings by their leaves, ideally the lower ones (the seed leaves or ‘cotelydons’), as a seedling can survive the loss of a leaf, but not the snapping of its stem!

Transplant each seedling to its own pot filled with general purpose compost, or to a tray where they are more spread out (a large seed tray should fit about 40 seedlings) if space is an issue. If you have put them into trays you will need to transplant them again, into pots, when they have grown on a bit more and before hardening off. Hold a leaf as you fill compost around the seedling so that the seed leaves (cotelydons) sit just above the compost and then firm in gently. This process is known as ‘pricking out’.

Grow the seedlings on in their new pots or trays and, after about another month’s growth, harden them off over a 1 to 6 week period (depending on the plant and the extent of the change in conditions) to their final climactic conditions.

Seedlings of bulbous plants should be kept in their initial pots for two growing season to allow the bulbs to develop, unless they need to be thinned out due to overcrowding. Water them well and feed with tomato fertiliser during their growing season to keep them active for as long as possible so they can bulk up their bulbous storage organ. Reduce watering and stop feeding while they are dormant (although some bulbous plants require watering year round). The seedlings can be potted on when they are dormant and the compost is nearly dry, ensure that you plant the bulbs the same way up as they were already growing. Allow them to grow on for another two years (and space accordingly) before planting them out.

Seeds sown in the ground

As the seedlings appear, thin out any weaker seedlings causing overcrowding (which can reduce the light, air and water available to each seedling). This is particularly important for grasses, which can rapidly become overcrowded. Thinning out is best done when the soil is moist and the weather is mild. When thinning out, put your finger gently at the base of the seedling to be kept, to minimise its disturbance, and gently pull out the weaker seedlings. The thinned out seedlings can, in some cases, be re-planted elsewhere in the seedbed.

Ensure that the seedbed is kept weed free and moist (watering with a fine rose or a seep hose to minimise the disturbance of the seeds/seedlings). The seedbed should be covered with horticultural fleece, cloches or straw if there is danger of frost.

Trees should be transplanted when they are one year old to grow on in a nursery bed, or in containers (so that they don’t become too well rooted in the seed bed).