Potted plants can be taken outdoors as soon as the risk of frost has passed, so that they can become accustomed to their new surroundings in a timely manner - except for tropical species and other plants that have overwintered in a heated room. Let the plants get used to the intense light for a week in a shady location. If there is a late frost, you can cover your plants with fleece or bring them back inside for a while.
Fresh soil for the new season
When all the soil has been colonized by roots, it’s time to repot the plant. Young plants especially grow very quickly and after 2 years require a pot that is 1-2 inches larger in diameter. Loosen the root ball gently and remove any old soil.
Older plants need larger gaps to grow into. When the container has already been filled by the roots, you can cut 3 wedges out of the root ball and fill the empty space you’ve just created with fresh soil. Quality soil is important, since it retains water well.
Only clivias and Agapanthus (such as Lily of the Nile) enjoy a cozily-filled pot. Only repot it when the plant is bursting out of the pot; divide it only rarely. Then set it in a shady location, water it frequently, and avoid fertilizing it for four weeks.