 His practical and systematic book both gives detailed descriptions of useful plants including leaf and root vegetables, herbs, spices and trees, and explains how to propagate and care for them.The twelfth century agronomist Abū l-Khayr al-Ishbīlī of Seville described in detail in his "Kitāb al-Filāha" (Treatise on Agriculture) how olive trees should be grown, grafted (with an account of his own experiments), treated for disease, and harvested, and gave similar detail for crops such as cotton.Medieval Islamic agronomists including Ibn Bassal and Abū l-Khayr described agricultural and horticultural techniques including how to propagate the olive and the date palm, crop rotation of flax with wheat or barley, and companion planting of grape and olive.