All perfect praise be to Allah, The Lord of The Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
It is confirmed in the Book of Allah as well as the Prophetic Tradition that crops and fruits are liable for Zakah. Allah, The Almighty, says: "but render the dues that are proper on the day that the harvest is gathered"{al-An`am/141}. In addition, Prophet Mohammad (PBUH) said: "A tenth is payable on what is watered by rivers, or rains, and a twentieth on what is watered by camels"{Muslim}.
Shafi`i scholars are of the view that Zakah is due only on crops and fruits consumed for sustenance, not for treatment or luxury. Therefore, Zakah of fruits is due only on grapes and dates; whereas, Zakah of crops is due only on wheat, barley, rice, lentils, corn, chickpea and beans. However, Zakah isn`t due on saffron and wars (a plant of yellow color in the Yemen, like sesame).
Al-Shafie said: "Zakah isn`t due on saffron or wars because many items of wealth aren`t liable for Zakah. Rather, Zakah is due when there is evidence from the texts of Sharia stating that. Saffron and wars aren`t consumed for sustenance and they aren`t liable for Zakah." {Al-Umm, v.2:41}.
However, Hanafie scholars are of the view that Zakah is due on whatever is planted for investing a land, so Zakah is due on fruits, vegetables, saffron, and other." According to Al-Sarkahsi, "…this is why Zakah is due on saffron." {Al-Mabsoot v.3:3}.
In conclusion, according to Shafie scholars, Zakah isn`t due on saffron. However, if the farmer sold the saffron, the money he has reached Nisaab (Minimum amount liable for Zakah), and a full lunar year passes over possessing that sum, then he must pay the Zakah of that money. However, whoever wants to be on the safe side may follow the view of the Hanafie scholars. And Allah the Almighty knows best.