[Ruling on Zakat for One Who Purchases a Qāt Plantation]

Answer: The jurists of the madhhab, as in al-Bayān, said: Whoever purchases a crop that has not yet ripened, and it then ripens while in his ownership (i.e., the buyer’s), the tithe (ʿushr) is due from the buyer.
They also said, as in al-Bayān: Whoever purchases fresh dates or grapes after most of them have ripened—if he cuts them immediately after the purchase, nothing is due from him; but if he leaves them until they are fully complete, the tithe is due upon him.
As for the seller of a plot of qāt, he must pay zakat; for the jurists of the madhhab said regarding one who sells a crop intending it for fodder or for sale that he must pay its zakat, as in al-Bayān. And qāt is a crop that is, in most cases, planted with the aim of sale.
This may be supported by His saying, Exalted is He: “And give its due on the day of its harvest.” [al-Anʿām:141].
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1