If a Ussurian pear (left) is pollinated by a ‘Flemish Beauty’ European pear (right), will it take on its taste? Photo: nps.gov, emojiry.com & Mikko Heikkinen, Flickr, montage: jardinierparesseux.com
Question: Following up on the article Fruit Trees: It Usually Takes Two, can the Ussurian pear (Pyrus ussuriensis) pollinate European pear trees, like ‘Flemish Beauty’ or others? And would its fruits then become edible thanks to the presence of European pear trees nearby?
Answer: The answer to the first part of your question is yes: the Ussurian pear (P. ussuriensis), also called Manchurian pear or Harbin pear, happens to pollinate the popular European or common pear (P. communis), even though the two are different species. In fact, it is an excellent pollinator, producing copious numbers of flowers and it is often used specifically as a pollinator in cold climates where there is little choice of European pear trees that can be used for cross-pollination. That’s because the Ussurian pear tree, from the extreme north of Asia, is very, very cold hardy (hardiness zone 3 or even 2) compared to the European pear tree, whose different cultivars are of variable hardiness: mostly zone 5, but sometimes zone 4 or, for the very hardiest ones, zone 3.
Ussurian pears, on the other hand, are not usually considered edible. Not that they are poisonous, but the small, globular, brownish-green fruits are small, hard as a rock and quite acidic and astringent, although after a good frost which increases their sugar level, it is possible to use the fruits in cooking. Due to their small size (at only 1 ½ inches/3 to 4 cm in diameter, Ussurian pears are no bigger than a golf ball!), there isn’t much flesh to harvest, though, and the rare times they are used as human food is usually by crushing them to extract their juice.
Cross Pollination Does Not Affect the Taste
On the other hand, cross-pollination between a Ussurian pear and a European pear will in no way improve the quality of the fruit of the former. Moreover, it’s the same thing for any cross between two different plants. With very few exceptions, the fruit resulting from such a cross will be identical in appearance, texture and taste: a typical fruit of the mother plant. Just transferring pollen to a flower does not change the fruit.
So, a pear produced on a Ussurian pear tree, but resulting from a cross with a European pear such as the ‘Flemish Beauty’ you mention, will always be small, round, sour and astringent. In other words, a typical Ussurian pear. It will show no trace of any European pear influence. And the opposite will also be true: a pear produced by a ‘Flemish Beauty’ pear tree but resulting from the cross-pollination from with a Ussurian pear will have the oblong, wide-bottomed shape and the color of typical ‘Flemish Beauty’, plus the same appetizing aroma and sweet and delicious taste it is supposed to have.
Therefore, the origin of the pollen that ensures fertilization will not change the quality of either fruit, neither for better nor worse.
If, on the other hand, if you harvest seeds from the hybrid fruit and sow them (and wait patiently: it can easily take 7–10 years for the first fruits to appear on a pear tree!), the fruits will show a mixture of traits from both parents. So, it’s in the second generation that the effect of cross-pollination is seen.
There are indeed quite a few hybrid pear trees resulting from crosses between the Ussurian pear and the European pear, called by convention P. × ussuriensis, of which the best known is ‘Ure’, a hardy pear tree (zone 3) with excellent disease resistance that yields an abundance of small, yellow pear-shaped fruits that are perfectly edible and delicious. In addition, it’s very ornamental, with abundant white blooms in the spring and superb fall coloring. Like most pears, ‘Ure’ is not self-fertile and will require a pollinator, preferably a Ussurian pear tree (P. ussuriensis), another hybrid pear tree (P.× ussuriensis) such as ‘Early Gold’, ‘Golden Spice’ or ‘Parker’ or even an Asian pear tree (P. pyriforme).
The Same Rule Applies to Other Plants
It’s the same situation for other plants, by the way. If two squash or two peppers cross in your garden, it won’t change the taste or appearance of the fruit in the first year, but if you save and sow the seeds, the second generation will be a hybrid one, with mixed traits and indeed, not always the most desirable ones.
In the Animal World Too
Besides, when you think about it, it’s the same with animals. If, for example, you cross a male Rottweiler with a female poodle, the latter will not begin to develop Rottweiler traits. However, all puppies from the cross will be hybrids and will have mixed traits.
It is therefore in the upcoming generation that crossbreeding shows its effects, in both plants and animals.
There are a very few exceptions to this rule, but two of them could affect how you garden.
Maize (Zea mays) differs from most other vegetables in that it undergoes a double fertilization: the pollen brought by the wind fertilizes both the embryo that will give a new plant, but also the endosperm, the grain we eat. So yes, the taste and even the color and texture of the kernel can be adversely affected by the presence of another corn variety growing nearby. Read Sweet Corn Hates Company to understand this unique situation.
The other common exception is the seedless English or greenhouse cucumber. This cucumber (Cucumis sativus) is parthenocarpic, that is, it produces fruit without being fertilized (which is why the seeds never develop). But if it is pollinated by a normal cucumber nearby, it will produce lumpy, irregular fruit with seeds. This is why it is usually grown in a greenhouse or in isolation to avoid crossbreeding. Read English Cucumbers Don’t Like Company for more information.
So, you can plant a Ussurian pear tree near your ‘Flemish Beauty’ pear tree to help it produce more numerous delicious fruit than ever, but the fruits produced by the Ussurian pear tree will remain Ussurian pears: small, hard and barely palatable. They’ll never take on the taste or appearance of a European pear.