Not all plants can be transplanted, root vegetables don’t like to be moved especially carrots which will result in losses and distorted roots. Others however positively benefit from being transplanted. Winter brassicas will form a stronger root system if they are transplanted first into a nursery bed, and then again into their final growing position 6 weeks later.
How to Transplant
Before you plant any crop that has you have started indoors out you should harden them off first. This means introducing them to the colder outdoor temperature gradually. You could do this by moving them to a well ventilated cold frame, or even leave them outdoors every day for a week, bringing them in before it gets cold in the evening, before eventually leaving them outdoors permanently. You should also (in most cases) wait until the risk of frost is over before planting out to minimise the risk to the young plants.
When transplanting any seedling, water both the soil and the seedling before you start. Lift the seedlings out of the tray gently, preserving as much of the root as possible, and handle the plant by the leaves and not the stem. Ease it out of the seed tray gently (an old blunt dinner knife is great for this), and then plant it in the ground by making a hole, with a dibber or using your finger, that is deep enough to cover the entire root. Alternatively you could continue to grow them on indoors by potting them into individual 9cm (3in) pots and growing them on indoors until a healthy rootball forms. This is especially useful when late frosts are a problem, or if you are growing more tender varieties.
Water any transplanted plant well (even if it is raining) and keep the soil moist while the plant establishes itself.