In the name of Allah, Most Compassionate, Most Merciful,
All types of plants and vegetation are lawful (halal) to consume, except when fermented to contain alcohol, intoxicants or other ingredients that may be harmful. As such, consuming mushroom is permissible.
Sayyiduna Sa’id ibn Zayd (Allah be pleased with him) narrates that he heard the Messenger of Allah (Allah bless him & give him peace) say: ‘Mushroom is from the al-Mann, and its water is a cure for the eyes.’ (Sahih al-Bukhari, no. 5381)
The great Hadith master, Imam Ibn Hajar al-Asqalani (Allah have mercy on him) gives two interpretations for the Messenger of Allah’s (Allah bless him & give him peace) statement ‘Mushroom is from the al-Mann’ in his monumental Fath al-Bari.
1) It refers to the al-Mann and Salwa that was sent down on the people of Sayyiduna Musa (peace be upon him) Banu Isra’il as a bounty from Allah Most High.
2) al-Mann is from the root word imtinan, which means blessings, favour and graciousness, meaning mushroom is a gift from Allah Most High, in that it grows after rain without having to do any farming. (See: Fath al-Bari, 10/202)
Thus, consuming mushroom is Halal. However, certain species of wild mushroom are poisonous for human consumption; hence one should exercise caution and avoid consuming such mushrooms.
And Allah knows best