Georgofili World

Newsletter of the Georgofili Academy

Climate change and fruit-bearing trees in temperate climates

European fruit-farming is mainly concentrated in Mediterranean countries, with most of the cultivars currently grown needing between 600-700 and 1000-1200 hours of winter cold (conventionally computed from October to February below 7.2°C), in line with the normal climate trend. With the progressive rise in winter temperatures that has accelerated in the last few years, cold weather is more and more frequently registered as no more than 500-600 hours, making again relevant a problem that had seemed resolved.
In the 1950s and 60s, many peach cultivars, mainly introduced from the United States (Georgia, Michigan, and New Jersey), had problems in southern Italy with their need for cold with the subsequent early drop of flower buds. The problem for this species was overcome following the importation of cultivars mainly from California and, for the milder southern areas, from Florida, two states whose climates are very similar to that of southern Italy.
The on-going climate change and the current distribution of fruit-farming, of apricot trees especially and of cherry trees in part in southern Italy (Basilicata and Sicily, in particular), is actually presenting the problem of environmental adaptability of various cultivars of these species. Many apricot and some cherry cultivars in the milder areas of these regions had an anomalous early drop of flower buds that means a drop in fructification vis-à-vis the orchard’s potential. This phenomenon is due to the provenance area of the majority of the new apricot and cherry cultivars. Almost all the new cherry cultivars were selected in British Columbia (Canada) and in Central Europe or they derive from trees coming from those places. Whereas almost the entire new generation of apricots was selected in France. The climate in those places is very different from that of southernmost Italy.
If climate warming continues at its current pace, ever larger areas in Mediterranean Europe will face the same adaptability problem that we are experiencing today in the southernmost regions. There is an immediate need for genetic improvement in order to face the problem by selecting various species of cultivars that do not require cold weather, as was successfully done for the peach tree.