The Pollination of Pear Trees
Pollination occurs in pear trees in the spring during the flowering stage. Different varieties of pears have varied blooming times by as much as three to four weeks, from mid-March to mid-April. In order for pollination to occur, pollen must be transferred from the female part of one flower to the male part of another. Without this, the pear tree is unable to produce fruit.
Self-fruitful plants are those that can produce fruit either by pollinating with another plant of the same variety or because it is self-pollinating. Pears are not self-pollinating as they require pollen from another tree. Some pears, however, are partially self-fruiting which is different from self-pollinating. Ideally, they require another tree of the same variety or another pear variety that blooms at the same time. Some Asian pears, such as Hosui, are capable of self-fruiting but perform better if they are cross-pollinated. Some common or European pears are also self-fruiting. Varieties include Orient, Baldwin, Kieffer and Spalding.
Interspecies Pollination Options
Some pears can also be pollinated by plants outside the pear family. Apples and crab apples are capable of pollinating pear trees because all three are part of the rose family of plants. In situations where both apples and pears are desired in the landscape but room is not available for more than two trees, one pear and one apple can be planted. The only concern is matching the bloom time of the two trees.
Bees are the primary pollinator of pear trees. Attracted to the flowers' nectar, bees will transfer the pollen from the carpal of one flower to the stamen of another. Other insects can act as pollinators, as well, but due to the relatively low sugar content of the nectar, most prefer other sources.
The location of the pear tree in relation to other sources of nectar can play a dramatic role in whether or not the tree gets pollinated. The 15-percent sugar content of the nectar must compete with the 40-percent content of competing plants, including apples and dandelions. If there are not enough bees in the area, the bees will choose the higher-sugar-content plants before pollinating the pear trees. Pears will have a higher pollination success rate if it does not have to compete with these plants for the bees’ attention. For small orchards, consider adding one or two beehives for every acre of pear trees.
As pears are not self-pollinating, they require pollination from another tree. This is complicated by the fact that pear trees of different varieties have different blooming times. The key here is to plant trees that have the same bloom time. Blooming periods can span several weeks and if the correct varieties are not blooming simultaneously, pollination will not occur. As there are dozens of varieties, it is prudent to check if the desired varieties have compatible bloom times.