Pollination of Tree Fruits Fact Sheet No. 7.002 Gardening Series|Fruits and Vegetables by A. Gaus and H. Larsen* Most fruit trees need cross-pollination for a pollinating variety in buckets of water and Quick Facts good fruit set and you may need to buy more hanging them in the trees. than just one variety. The honeybee is the most important • Before purchasing trees, Many new plantings, especially apple carrier of pollen. In mature orchards, there evaluate the pollination orchards, are planted in a solid block of should be a minimum of one hive per acre requirement of the given fruit one variety to make more efficient use of (two hives per acre in pear orchards). Pollen crop. land, labor and cultural practices (thinning, transfer is seldom done by wind. Backyard pruning, chemical sprays, harvesting). For plantings probably have enough wild bees to • Place pole-type pollinators pollination, place pole-type pollinators every do the job. every 60 to 120 feet in every 60 to 120 feet in every row, with adjacent Some orchard cover crops, such as row, with adjacent rows offset. rows offset. These pollinizer trees, trained as a dandelion blooms, are very attractive to bees. • The honey bee is the most pole-type or slender spindle, take up little or Remove the blooms by mowing or herbicide important carrier of pollen. no productive space in the orchard but give sprays to increase pollination for apples. maximum fruit set potential. For backyard Bees are not active in cool, wet or windy • All varieties of apples require trees, a pollen source, such as a neighbor’s weather. More bee colonies may be needed in some cross-pollination. crabapple tree, should be no more than 100 such weather. feet away. • All sour cherries are self- In established orchards without adequate fruitful. All sweet cherry pollinizers, the top of every third tree in every Apple varieties, except Stella, are third row may be grafted to a pollinizing All varieties of apple trees require some self-unfruitful and must be variety. In backyard situations, you may want cross-pollination for fruit set. Even though cross-pollinated. to graft a pollinizing variety on one of the some varieties are listed as self-fruitful, they scaffold limbs. Bouquets also may be used by will set fruit more heavily and more regularly • Common varieties of placing branches of open, fresh blossoms of if they are cross-pollinated. For solid block nectarines and most peaches grown in Colorado are self- fruitful.

Figure 1: Pollination of apples.

*Colorado State University Extension fruit specialist, Rogers Mesa Research Center, Hotchkiss. 4/96. ©Colorado State University Reviewed by H. Larsen, Colorado State University Extension. 4/96. Reviewed 10/09. Extension fruit pathologist and professor; horticulture and landscape architecture, Orchard Mesa Research Center, www.ext.colostate.edu Grand Junction. 10/09 plantings, spur-type Winter Banana, spur-type Golden Delicious, or flowering Definitions crabapples such as Manchurian and Pollination: the transfer of pollen from Snodrift may be used for pollinizers. Place honeybees in apple orchards when the anthers to the stigma of a flower. the first blossoms open. Self-pollination: when the transfer of pollen occurs within the same variety.

Peach, Nectarine Cross-pollination: when the transfer and Apricot Figure 2: Pollination of pears. of pollen occurs between two varieties. The common varieties of Colorado Self-unfruitful: very little fruit will set nectarines and most peaches are self- Pear unless the blossoms are fertilized with fruitful (J.H. Hale, Earlihale, Hal-Berta, Anjou and Bartlett are partially self- pollen of another variety. Candoka and Mikado; Elberta in June). fruitful but should be cross-pollinated Most other varieties of peaches will to produce heavy and regular crops. Self-fruitful: varieties that set fruit with pollinate these self-unfruitful varieties. Bartlett, Comice and Hardy may set large their own pollen. However, Elberta is not a good pollinizer crops of parthenocarpic fruit. Another for J.H. Hale. Self-fruitful varieties of consideration is the fire blight susceptibility Cross-unfruitful: two varieties that, apricots are Tilton, Wenatchee, Royal and of the pear cultivar, because the pollen when cross-pollinated, will not set fruit. Moorpark. These will set commercial crops source is useless if stunted or killed. (See Compatible: varieties that fertilize without cross-pollination. Self-unfruitful fact sheet 2.907, Fire Blight.) each other. varieties of apricots are Riland, Perfection Pear blossoms have a short season and and Rival. Any self-unfruitful varieties can the small amount of nectar produced is Parthenocarpic: fruit that is set and be pollinized by any other variety. not attractive to bees. Twice as many bees grown without fertilization (no seeds should be available to pears than for other present). fruits. Move bees into the pear orchard Sour and Sweet Cherry when the trees are in one-third bloom. All sour cherries are self-fruitful, such as Montmorency, North Star, Balaton, Meteor, English Morello, Early Richmond, Plum Hansen Bush Cherry and Nanking. Two of the most popular varieties of Most sweet cherries are self-unfruitful Japanese plum, Burbank and Abundance, (self-incompatible, SI) and require cross are self-unfruitful but will pollinize each pollination with another variety as the other. Because of bloom date differences, do pollen source. not rely on European varieties to pollinize Some varieties, e.g. Bing, Lambert, Royal Japanese varieties. Ann/Napoleon, are also cross-unfruitful Stanley and Damson are self-fruitful and cannot be depended upon to provide and will pollinize other European varieties. pollen for each other. Index, Lapins, Skeena, All other European plums require pollen Sweetheart, WhiteGold, Sonata, Stella, from another European variety. Symphony, Sunburst, and BlackGold are self-fruitful (SF) sweet cherries that can serve as “universal” pollen sources for many self-unfruitful sweet cherry varieties (Stella does not work for Bing in some areas). Their use as “universal” pollinators should also take bloom timing into consideration as follows. Early-bloom: SI – Somerset; SF – Lapins and Skeena. Early- Figure 3: Pollination of Japanese plums. to early-mid-bloom: SI – Kristin, Chelan, and Black Republican; SF – Sweetheart and WhiteGold. Mid- to late-mid-bloom: SI – Royalton, Summit, Ranier, Royal Ann / Napoleon, Bing, Burlat, Van, Regina, Lambert, Sam, and Windsor; SF – Sonata, Stella, Symphony, and Sunburst. Late- Colorado State University, U.S. Department of bloom: SI – Gold and Hudson; SF – Agriculture and Colorado counties cooperating. BlackGold. Move bees into orchards on the CSU Extension programs are available to all without first day of bloom. discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.