Much debate has been occurring regarding the requirements of chill hours for sweet cherry trees to properly break dormancy and set a reasonable crop.
Looking into this subject using either the chill hour model from 1950 (orchard hours greater or lower than 7.2C), or the chill portion model from the dynamic model of 1987; the facts are that if there is insufficient chill time during winter dormancy, crop failures may occur.
Usually a cherry cultivar or variety has a known approximate number of chill hours or chill portions required to set fruit. However, this may vary depending on where trees are sourced from or grown. For instance, Lapins (bred in Summerland, British Columbia, Canada) require over 700 hours of chill in some regions of Italy, while in California, Lapins require less than 500 hours.
Elevation and latitude also may have a bearing on chill requirements. We know that travelling north or south in a country makes a difference to harvest dates; and that an extra 100 metres in elevation might add five days to the time of harvest for a particular variety.
What does this mean to a grower wanting to crop cherries in a given location?
It’s just as important to know the chill requirement for a variety growing in your region, as it is choosing the best pollinator (for a non self-fertile variety), in order to have the best chance at cropping in your location.
Do the research because there is no room for a cherry variety that does not earn (economically) its place in the orchard.
For more information, see Tree Fruit April 2014
