A large amount of information exists about medieval agriculture and ways-of-life in general (See Chris Dyer's book, Making a Living in the Middle Ages for good background), the [large] role of monasteries in medieval agriculture (See Cistercians and the salvation of Western Civilization), as well as monastic diets that varied by monastic order (See Bridget Henisch's book Fast and Feast: Food in Medieval Society or Barbra Harvey's Living and Dying in England 1100-1540: The Monastic Experience). Medieval monasteries were huge land owners, engaged in trade, and integral to the surrounding community (See Janet Burton's "Monastic Economy" in Monastic and Religious Orders in Britain).

If I understand your question correctly however, you are asking specifically about medieval monastic agriculture, and convents can be added to this question/answer as well. If so, monastic diets reveal that nothing would have been particularly "monastic" about what was being grown. Generally, medieval agriculture and diet was dominated by grain for both bread and beer. While your question only asks about flora, aside from raising livestock (e.g., sheep for milk and cheese for export, wool for textiles and export, and manure for fertilizer), there were also more grapes in particular, which was necessary for making wine, both for sacramental use and for sale and export (See Jancis Robinson's Oxford Companion to Wine), and medicinal herbs, since monasteries also functioned as hospitals. With regards to climate and terrain, what was grown absolutely varied by regions, as it does today, and trade (import/export) continues to provide places with foods that can't be grown.

Hopefully other more knowledgeable people can weigh in on your questions as well. At this moment, I really hope your question wasn't asking about medieval Buddhist monasteries in Asia. Otherwise, I have been way, waayy, off.