Nizami Ganjavi is one of the foremost figures in Persian poetry, living in Azerbaijan in the second half of the twelfth century. One of the oldest Western poets in Persian literature, he is acclaimed for his five masnavis which are assembled to form the Khamsa (Quintet). His reputation is that of a difficult and refined poet, who introduced into his verse vocabulary, expressions and allusions to the then-known sciences. This study considers all his verses containing allusions to trees and their fruit. The scientific contents of these allusions are then checked with the help of Arabic and Persian medieval scientific treatises, ranging from the ninth to the seventeenth century. As a result, this study not only proposes a better understanding of nature imagery in the work of a seminal Persian poet, but provides a useful insight into the breadth and depth of the education of medieval poets and their readers.