Winter Cold and Chilling Hours May Not Be Cherry Problem

Sweet cherry growing in North Las Vegas Nevada

Q. I have a two-year-old pie cherry tree that needs so many days of cold weather to set fruit next year. Should I cover it with burlap for the winter? And if I do, then should I also cover the trunk or just the branches?  

English Morello sour cherry in North Las Vegas Nevada

A. How much protection you give it during the winter depends on where you live and your lowest temperatures during winter. Cherries are divided into two categories; sweet cherries and sour cherries. Sweet cherries are for eating fresh, out of hand. Sour cherries are considered “pie cherries” and used fresh or canned.

            Sour cherries grow as far north as Michigan so I don’t think low temperatures are going to be a problem unless you live in northern climates. If you don’t live that far north, you don’t need to protect them through the winter.

Bing cherry produced on sweet cherry tree in North Las Vegas Nevada. Don't get excited. Twenty-five sweet cherry trees of six varieties produced twelve cherries in twelve years. Backyards in other locations in the Valley, sweet cherries were plentiful.

            Chilling hours is the number of hours needed below 45°F to recognize winter is finished. When the number of chilling hours have been met, the plant waits for warm temperatures of spring so that it can begin flowering again.

            Chilling hours are important but I think they are sometimes overestimated by growers and scientists. In the Las Vegas Valley, our chilling hours are estimated to be somewhere between 300 to 400 hours depending on winter temperatures.

            I have grown five sour cherries in the Las Vegas climate and have had no problems with flowering even though many of them are rated between 400 to 500 hours. I have had problems getting fruit from the flowers. A lack of chilling does not appear to be a problem for sweet and sour cherries grown in Las Vegas.

            I think the problem of setting fruit in the desert is more likely a humidity problem. Trees growing in backyard residences with pools or lawns set fruit each year in the Mojave Desert. Low humidity and failure to set fruit is a common problem with many tropical trees, with 30% relative humidity seeming to be the lower limit for successful fruit set.