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Wait until all threat of frost has passed and the soil has had a chance to heat up a little before planting the rhizomes outside again. Mid-spring is usually a good time to move them outside again. Keep in mind that if you can't find a super sunny spot, Callas will tolerate shade for part of the day. It's a good idea to incorporate some well-rotted manure or compost into the soil to improve it ahead of planting. A rich soil will help the plant produce flowers. The rhizome should be planted with the 'eyes' facing upward and just visible at the top of the soil. These are the growing points that look like the 'eyes' on a potato. Leave about 12 inches (30.5cm) of space between each of your rhizomes. Once they are in the ground, give them a good soaking and then continue to keep the soil moist but not waterlogged as they grow. Calla Lilies require water throughout the summer. If you dig them up for overwintering indoors, they will need extra water as they get established back in the ground. Remember to feed fortnightly during the growing perioda water-soluble fertilizer added to the watering can is idealbut stop feeding ground-planted Calla lilies once flowering begins. Continue feeding container-grown Callas throughout the flowering period. Callas are generally trouble-free but can suffer from pest attacks by aphids or whiteflies. Keep an eye out for pests and spray as required with an all-purpose bug spray.
Do not plant your Calla lily until you are sure there will not be any more frost. Choose a well-drained spot in a sunny position. Plant your rhizome correctly. Water your Calla lilies. Watch out for pests.