Simplify the following text for a Grade 12 native English-speaking person.
Original: Ancient Persians cultivated Persian saffron ( Crocus sativus ` Hausknechtii ' ) in Derbena , Isfahan , and Khorasan by the 10th century BC .
Simplified: Ancient Persians were growing their own type of saffron ( Crocus sativus ` Hausknechtii ' ) in Derbena , Isfahan , and Khorasan by the 10th century BC .