sazrevati

1. (of fruit) to ripen
   Trešnje u našem kraju sazrevaju krajem maja. — In our area cherries ripen at the end of May.
2. (of a person) to mature; to grow up
   Devojčice obično brže sazrevaju od dečaka. — Girls usually mature faster than boys.
3. (of an idea or situation) to mature; to take shape
   Ideja o selidbi polako je sazrevala u njemu. — The idea of moving was slowly taking shape in his mind.

The perfective is sazreti.