Seedlings can be transplanted when they have developed two sets of leaves. This is also the time to thin the seedlings that are growing too close together.
A seedling needs rich soil similar to the soil in which it was started. Plants should be placed one per pot or 2 inches apart in the ground. Handling the seedlings by the leaves helps prevent damage to the fragile stems and roots. Transplant the seedlings outdoors after the last freeze of the season has passed to avoid killing the seedlings. Regular watering, plenty of sunshine and later fertilizing keeps the plants healthy and strong.