Iron deficiency (iron chlorosis) is considered the most widespread nutritional disorder of plants. The particular susceptibility of fruit crops for this disease raises the costs of the cultural management owing the necessary remedial practices applied to impair its negative effects. Visual diagnosis (plant observation at naked eye) is a cheap, fast and reliable method for identifying iron deficiency. As a previous information, in this paper was considered appropriate to summarize the most important factors and causes leading to iron deficiency. Later, an actualized description of the characteristic disease symtoms is reponed. Finally, a set of original colour pictures is included as an example of visual diagnosis applied to 25 woody species: almond, apple, apricot, Asian pear, blackmulberry, blackberry, blackthorn, carob, feijoa, fig, grapevine, hazel, kiwi, loquat, mandarin, olive, orange, peach, pear, plum, pomegranate, quince, redraspberry, sweet cherry, walnut.