Picking the Right Pollen Buddies for Top Fruit Production in a Temperate Climate
By Louise Lambert
Many fruit trees are self-sterile, that is to say that their pollen cannot fertilize the flowers of the same cultivar. One ‘McIntosh’ apple, for example, won’t be able to pollinate either its own flowers or the flowers of another ‘McIntosh’. Others are partially self-fertile and may produce some fruit with grown alone, but not very many. Finally, some fruit trees are dioecious, that is the male and female flowers are borne on different plants. Obviously, for these varieties, you’ll always need a least one male plant to pollinate nearby females.
Therefore, for the majority of fruit-bearing plants, 2 cultivars (varieties) that are different and yet compatible will be needed to ensure the pollination necessary for fruit production. They need to be of the same type, bloom at the same time, etc.
Helpful Hint: For most species, the maximum recommended distance between compatible fruit trees is 100 feet (30 m). Otherwise, the bees can’t do their job of carrying pollen from flower to flower.
This short article is intended as a note that home gardeners in temperate climates can use to identify, for each fruit tree seeking a bit of pollen to use, partners that it will be compatible with or the particular conditions that need to be respected in order to produce fruit.
For some fruit trees, this compatibility is presented in the form of a table.
Sea buckthorn is a dioecious plant: each plant bears the flowers of a single-sex. It requires at least one male plant and one female plant to produce fruit! The kiwi (Actinidia spp.) is another dioecious plant.
Highbush Blueberry (V. corymbosum)
Lowbush Blueberry (V. angustifolum)
The above species of blueberries and others are weakly self-fertile. The recommendation is to grow at least two different cultivars in the same group (two highbush or two lowbush) in close proximity, ideally three. Oddly, many nurseries sell blueberries as being self-fertile. While that may be technically true, it’s unfortunate that they promote this aspect, as blueberries produce much less on their own and should really be planted with a partner.
Currant and Gooseberry
Currants, gooseberries, elderberries and almost all other small fruits are considered partially self-fertile. Since cross-pollination makes them much more productive, it is best to plant two cultivars of the same type close together.
Generally, apple trees are self-sterile. It takes two apple trees of different varieties to ensure pollination. Since all the thousands of apple varieties belong to just one species, M. domestica, they can theoretically all pollinate each other. Yes, it’s true that some (although very few) apple varieties are pollen-sterile and some early and later-blooming varieties might not cross because their blooming periods don’t quite overlap, but unless the salesperson in the nursery where you buy your plants tells you otherwise, you can just assume that any apple tree you purchase will pollinate any other.
Furthermore, at least in temperate climates, crabapples are widely planted as ornamental trees in cities, towns and in the countryside. Since crabapples are just apples (M. domestica) under another name, they are excellent pollinators for all apple trees. And means that, unless you live in total isolation, it’s unlikely that an apple tree won’t find a pollinator already present and within easy reach. So, most home gardeners needn’t really need to concern themselves about apple pollination: it will take care of itself!
Haskap or Honeyberry
The haskap or honeyberry (read more about them in the article “The Fruit That Came in From the Cold”) is a shrubby honeysuckle also called blue honeysuckle because of the color of the berries. All haskaps are self-sterile, so two varieties (or more) are always necessary.
However, it’s not quite that simple. Several studies have identified compatible varieties and their compatibility depends on several factors, including their flowering period and even the structure of the flower itself. The following table can help you choose two that go well together.
Chart supplied by Martine Girard, Vegetolab.com.
Apricot trees are generally self-fertile and compatible with each other.
Sweet cherry (P. avium)
Sweet cherry trees (P. avium) require the presence of another variety of sweet cherry tree to promote pollination.
Sour cherry (P. cerasus)
Sour cherry trees (P. cerasus) are generally self-fertile, but perform best in the presence of another sour cherry.
Dwarf sour cherry (P. × kerrasis)
This shrubby cherry, developed in Saskatchewan, is becoming rapidly popular and is self-fertile. Still, planting a different cultivar nearby will help increase the yield.
“4 in 1” cherry trees have four different cherry cultivars grafted onto the same tree. They are all of the same type and will readily their neighbors.
Different species of bees ensure the pollination of the vast majority of fruit trees and small fruits. Avoid applying toxic pesticides when they are around!
European plum (Prunus domestica)
American plum or wild plum (P. americana), native to the eastern US and Ontario
Canada plum or black plum (P. nigra),
Japanese plum (P. salicina)
American-Japanese hybrid plum (P. cvs)
As a general rule, plum trees are compatible within the same type.
The Canada plum (P. nigra), native to Canada and the northern US, is the best pollinator for all American and Asian plum trees, as well as their hybrids. The American plum (P. americana), native just a bit further south, is also an excellent pollinator for species in this group.
“4 in 1” grafted plum trees are self-fertile, since they are composed of more than one variety within the same type.
European pear or common pear (P. communis)
Ussurian pear, Harbin pear or Manchurian pear (Pyrus ussuriensis)
Asian pear or Chinese pear (P. pyrifolia)
As a general rule, pear trees are self-sterile. It takes two pear trees of different varieties to ensure pollination. Pear trees are compatible within the same type (European pears with European pears, etc.). Some pear trees are weakly self-fertile, but perform best when accompanied by a different cultivar of their type.
About the Author
Louise Lambert is a consultant at Fleuri-Cap garden center in Quebec. A passionate gardener, she accompanies customers in their choice of plants from among a wide selection of annual flowers, vegetable plants, perennials, trees and shrubs.