Answer: Petunias are grown as annuals in cold winter areas because they do not withstand cold temperatures. In a warmer climate they will live longer.
Petunias can be pinched back (remove just the growing tip) when they reach a few inches tall. This will force branching. Theymay be pinched again when they have grown a few more inches, but further pinching will delay flowering. Note that some varieties are naturally more branching and bushier than others.
Healthy, stocky transplants will have roots filling the pack or pot and will be able to support themselves when planted. They should be planted at the same depth or barely deeper than they grew in the original pot. Planting them extra deep is not helpful as it may in itself cause problems.
If your plants are extremely weak and leggy, they may have been overfertilized with nitrogen or they may be in need of additional light. Most gardeners find it necessary to use supplemental lights such as shop lights turned on for about 16 hours a day in order to produce good quality transplants at home.
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