Is it permissible to plant in another person’s plot of land?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
Generally, we are prohibited from wrongfully using or utilizing the property of another person. This is clear based on the statement of Allah SWT:
يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَأْكُلُوا أَمْوَالَكُمْ بَيْنَكُمْ بِالْبَاطِلِ
“O you who have believed, do not consume one another’s wealth unjustly.” 
Al-Maraghi said: “Unjustly” means useless while according to the religious term it is to take the property of another without an appropriate return or permission from the owner. 
Syeikh Prof Dr Wahbah al-Zuhaili said the meaning of consuming the wealth of another unjustly is through various means that are not syar’ie such as usury, gambling, ghasb (oppression) and deception in trade. 
From Anas bin Malik RA, the Prophet PBUH said:
لَا يَحِلُّ مَالُ امْرِئٍ مُسْلِمٍ إِلَّا بِطِيبِ نَفْسِهِ
“And a man’s property may not be taken except with his goodwill.” 
Basically, this matter has been clearly explained in one of the hadiths of the Prophet PBUH where it narrates the story of a man who planted a date tree on the land of an Ansar. The matter is explained in a hadith narrated from Samurah bin Jundub RA:
أَنَّهُ كَانَتْ لَهُ عَضُدٌ مِنْ نَخْلٍ فِي حَائِطِ رَجُلٍ مِنَ الأَنْصَارِ قَالَ وَمَعَ الرَّجُلِ أَهْلُهُ قَالَ فَكَانَ سَمُرَةُ يَدْخُلُ إِلَى نَخْلِهِ فَيَتَأَذَّى بِهِ وَيَشُقُّ عَلَيْهِ فَطَلَبَ إِلَيْهِ أَنْ يَبِيعَهُ فَأَبَى فَطَلَبَ إِلَيْهِ أَنْ يُنَاقِلَهُ فَأَبَى فَأَتَى النَّبِيَّ صلى الله عليه وسلم فَذَكَرَ ذَلِكَ لَهُ فَطَلَبَ إِلَيْهِ النَّبِيُّ صلى الله عليه وسلم أَنْ يَبِيعَهُ فَأَبَى فَطَلَبَ إِلَيْهِ أَنْ يُنَاقِلَهُ فَأَبَى . قَالَ ” فَهَبْهُ لَهُ وَلَكَ كَذَا وَكَذَا ” . أَمْرًا رَغَّبَهُ فِيهِ فَأَبَى فَقَالَ ” أَنْتَ مُضَارٌّ ” . فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم لِلأَنْصَارِيِّ ” اذْهَبْ فَاقْلَعْ نَخْلَهُ ”
“He had a row of palm-trees in the garden of a man of the Ansar. The man had his family with him. Samurah used to visit his palm-trees, and the man was annoyed by that and felt it keenly. So he asked him (Samurah) to sell them to him, but he refused. He then asked him to take something else in exchange, but he refused.
So, he came to the Holy Prophet (ﷺ) and mentioned it to him. The Holy Prophet (ﷺ) asked him to sell it to him, but he refused. He asked him to take something else in exchange, but he refused.
He then said: Give it to him and you can have such and such, mentioning something with which he tried to please him, but he refused. He then said: You are a nuisance. The Messenger of Allah (ﷺ) then said to the Ansari: Go and uproot his palm-trees.” 
In this issue, as we see it, if the land’s owner permits him to plant trees on his land, then it is not an issue. If the owner of the land wanted his land back, then the plater must uproot his trees and clean the land just like before. However, if there is damage to the land, then the planter should be fined or replace the land so that it returns to its original state. Furthermore, the owner can also charge rent on the planter for as long as he is utilizing the land.
In our opinion, the owner doesn’t have any right over the planted trees, however, the owner can ask the planter before eating anything from the planted trees. This follows the clear evidence from the Quran that states:
وَلَا تَأْكُلُوا أَمْوَالَكُم بَيْنَكُم بِالْبَاطِلِ
“And do not consume one another’s wealth unjustly,” 
As for the planter, he must ask for permission from the land’s owner before he plants anything on land that is not his. The reason is this would lead to harm and burden to the land’s owner. This is clearly seen in the hadith of the Prophet PBUH:
لاَ ضَرَرَ وَلاَ ضِرَارَ
“There is no injury nor return of injury.” 
It is best if a written agreement is first made before planting anything on the land of another person. Lastly, may Allah ease our daily affairs in understanding and learning the teachings of Islam. Amin.