Sweet cherries (P. avium) do best in mild, dry climates, but some cultivars will do well in other climates with a little special care. Most sweet cherries need a second compatible cultivar for pollination. Certain sweet cherries can't pollinate other specific cultivars, so check before you plant. If you can only plant one tree, buy one grafted with two cultivars, or try a self-fertile cultivar such as Compact Stella or Starkcrimson. Sweet cherries can grow into trees 35 feet or taller, but they're also available on dwarfing rootstocks that will keep the trees as small as 10 feet. They are hardy in zones 5–7 and also thrive in zones 8 and 9 in the Pacific Northwest.
Sweet cherries come in purple, red, and yellow. There are firm-fleshed types and soft-fleshed types. Soft-fleshed types tend to be less prone to cracking.
Duke cherries are hybrids between sweet and tart cherries, and tend to be sweet/tart.
Bush cherries (P. besseyi, P. tomentosa, and Prunus spp.) bear small cherrylike fruit and grow well in areas with harsh winters where cherry trees will not.
Tart cherries are small trees no matter what rootstock they are grafted on. Standard sweet cherries are grafted on seedling rootstocks such as Mazzard (P. avium) and Mahaleb (P. mahaleb). If your soil is heavy, try Mazzard. For lighter soils, choose Mahaleb for a smaller tree that bears in 2 to 4 years. Mahaleb also adapts well to irrigation and slightly alkaline soil. Damil rootstock makes a sturdy dwarfed tree and appears even more tolerant of wet soil than Mazzard, but some of the dwarfing rootstocks available give disappointing results.
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Planting and Care
Tart cherries grow well throughout much of the United States. They need about 1,000 chill hours below 45 degrees Fahrenheit in winter. This limits their range to the Carolinas and northward through zone 4. Although all cherries need well-drained soils, tart cherries tolerate moderately heavy soils better than sweet cherries. Space tart cherries 20 to 25 feet apart, sweet cherries 25 to 30 feet apart. Dwarf trees can be planted with closer spacing.
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Sweet cherries are not as winter hardy as tart cherries. Early autumn frosts also can damage sweet cherry trees. Commercially, sweet cherries grow best in the West, where summers are dry.
Cherries bloom early and are susceptible to frost damage. Sweet cherries bloom earlier than sour cherries.
Once the fruit sets, watch soil water levels. Cherry fruit matures early and fast. It is particularly sensitive to moisture availability in the last two weeks of ripening. If the soil is too dry, the swelling cherries will shrivel. If it is too wet, they will crack and split. If you live in an area prone to heavy summer rainfall, choose cultivars that resist cracking. Spread a thick organic mulch out to the drip line to help maintain soil moisture at a constant level. Irrigate as necessary to keep the soil evenly moist.
Healthy cherry trees will grow about 1 foot per year. If your tree's progress is slower or the new leaves are yellow, have the soil and/or foliage tested for nutrient deficiencies. Mulch each spring with a thin layer of compost out to the drip line. Don't fertilize after midsummer. This could encourage new growth that won't harden before fall frosts.
A central leader form is best for dwarf tart cherries. Use a modified central leader form for semidwarf and standard cherry trees. Spreading the branches while they are young will help control height and encourage earlier bearing. After the trees reach bearing age, prune to let light penetrate to the interior of the tree. Prune tart cherries lightly each winter to stimulate new growth and thin tangled branches. Prune sweet cherries less frequently, only every third or fourth year. Cut back heavy tops on overgrown sweet cherry trees to force new fruiting wood to develop on lower branches.
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Fruit cracking and hungry birds are two of the biggest problems when raising cherries. Most insect and disease problems are less severe on tart cherry trees than on sweet.
Birds can strip all of the cherries off a few backyard trees in very little time. Covering trees with netting before the fruit starts to ripen is the most effective way to stop bird damage. You can also try planting a mulberry tree nearby that fruits at the same time as your cherries to lure birds away from the harvest.
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Cherry fruit fly, green fruit worm, peach tree borer, mites, and plum curculio all attack cherries. Aphids and scale can also cause problems. Sawfly larvae (pearslugs) sometimes skeletonize cherry leaves.
Shothole borers can attack cherries and other fruit trees. They make small holes in the bark of twigs and trunk. The holes are often covered with gum. The larvae are pinkish white and about 1/8 inch long. Prevent the tiny black adults from laying eggs by painting trunk and large branches in spring, summer, and fall with white latex paint diluted 1:1 with water. These pests most often attack wounded or diseased trees, so their appearance may be a sign that your trees are in trouble and you need to consider removing them.
Pear thrips can cause disfigured leaves and blossoms. Naturally occurring predatory mites usually provide control, but if your trees become severely infested, spray with insecticidal soap. (Here's how to make a safe and effective natural pest spray.)
Diseases can be a serious problem on cherries. Watch for brown rot and perennial canker that attack cherries and other stone fruit. Black knot can also attack cherries. Cherry leaf spots appear as small purple spots on upper leaf surface and these spots later turn brown and their centers may fall out. Leaves turn yellow and drop before autumn and should be cleaned up and disposed of each winter. If leaf spot is a problem in your area, plan a preventive spray program with lime sulfur or sulfur. Lime sulfur may discolor fruits, so don't use it after young fruits begin to develop. Powdery mildew can also be a problem on cherries. Buying virus-free stock and avoiding planting in old cherry orchards or near wild chokecherries can help prevent a number of viruses from attacking cherries.
When the fruit begins to drop, it is ready to pick. Tart cherries can be left to sweeten on the tree for a day or two.
To pick cherries, gently pull off clusters, keeping the stems on the fruit. Be careful not to tear off the fruit spurs (small woody twigs to which the cherry stems are attached).