Cold requirements of the apricot tree (Prunus armeniaca L.)

The cold requirements of five clones of apricot tree (Prunus armeniaca L.) were studied in Abaran (Murcia, Spain). The amount of cold received by the plant was estimated in cold units following three methods: exponential, Ric hardson and hours of cold. Under the conditions of Abaran, cold quantificat ion produced similar results for the three calculation methods used. The am ount of cold required by these clones for flowering ranged between 50 and 8 0 cold units calculated in accordance with the exponential method.