no. 522 for the year 2004 which includes the following:
The petitioner's father owns a number of palm trees. He would sell their fruits before they ripened and receive the price in monthly installments. What is the legal ruling for this?
 

The Hanbali scholars, Harb al-Karmani and Abu al-Wafa` Ibn 'Uqail, maintained that this form of transaction is rectified by changing the sale contract into a rental one. Ibn Taimiyya chose this opinion and maintained that it is tantamount to the consensus of the salaf [predecessors]. However, it is well known that the scholars of the four followed schools of jurisprudence contended differently. Harb al-Karamani mentioned that Sa'id Ibn Mansur narrated, "'Ubad Ibn 'Ubad related to us through Hisham Ibn 'Urwa through his father who said that Asid Ibn Hudayr passed away while he was indebted with six thousand dirhams. So 'Umar called his creditors and rented out to them Usayd's land, which included palms and other trees, for several years." In this instance, renting is permissible because a benefit is derived while the source itself remains constant and is renewable by Allah. This corresponds to benefits such as fruits from trees, milk from a wet nurse, and wool from sheep.

The ruling
It is permissible for the owner to rent his palm trees or other trees to the trader who will irrigate and fertilize them, ward off tree damage, and harvest their fruits for a determined period in return for a known fee. Therefore, this does not fall under the Prophet's prohibition concerning selling unripe produce.
Allah Almighty knows best.