The fruits of sweet cherry trees (Prunus avium) are among the first fruits of summer, and sweet cherries are used as landscape trees because of their dark, striated bark and profusion of pink blossoms in spring. Depending on the variety, sweet cherries are hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 4 through 10 and are commonly grown in California's long central valley. USDA zones 5a through 11a encompass southern California, though the majority of the region falls in USDA zones 8 through 10.
Sweet cherries do well in southern California as long as they are low-chill varieties. Winter chilling is measured in the number of hours an area spends between 32 and 45 degrees Fahrenheit, and few southern California areas receive more than 500 chill hours. A number of sweet cherries were bred specifically for the region's mild-winter climate, but only a few are self-pollinating, or self-fertile. Sour cherry trees (Prunus cerasus), the fruits of which are used for cherry pie, are all self-fertile, but very few have low-chill requirements. Sour cherries are hardy in USDA zones 4 through 9.
The sweet cherry tree "Lapins" (Prunus avium "Lapins") produces large, dark-red, sweet cherries and needs only 400 to 500 hours of winter chill. Its fruits are often compared to those of "Bing" cherry tree (Prunus avium "Bing"). "Bing" cherries are commonly sold in supermarkets. Sometimes "Lapins" cherry tree is labeled "self-fertile Bing" in nurseries. "Lapins" and "Bing" trees are hardy in USDA zones 5 through 9. "Lapins" fruits are resistant to cracking when rained on; cracking is one the greatest challenges in growing cherries.
"Stella" (Prunus avium "Stella") is one of the genetic parents of the "Lapins" cherry and begins to produce fruits at a very young age. The fruits mature late in the cherry season, and the tree needs about 400 hours of winter chill to produce fruits. The fruits are large, black and very sweet; they also are heart-shaped and show good resistance to cracking in wet weather. "Stella" is hardy in USDA zones 5 through 9.
Low-Chill Sour Cherries
Most sour cherries are adapted to climates colder than southern California's climates. "English Morello" (Prunus cerasus "English Morello") and "Montmorency" (Prunus cerasus "Montmorency") sour cherry trees, however, set fruit with about 500 hours of winter chill. "English Morello" produces dark, almost black fruits late in the season. "Montmorency" is a heavy-bearing, mid-season variety; its fruits have light-red skin and yellow flesh. Both varieties are hardy in USDA zones 4 through 9.
One way to have a self-fertile cherry tree is to graft multiple cherry varieties onto its trunk. Two of the most recently developed low-chill varieties, "Minnie Royal" (Prunus avium "Minnie Royal") and "Royal Lee" (Prunus avium "Royal Lee"), have extremely low chilling requirements and are ideal for the mildest regions of southern California. Both are hardy in USDA zones 6 through 10 and were bred to pollinate each other, making them a grafting pair option.