THE POLLINATION OF CHERRIES
We cannot complain in New York of much uncertainty in the setting of the cherry crop. Late spring frosts occasionally catch the blossoms of Sweet varieties but seldom those of the Sour sorts. Cold weather, especially if accompanied by wet weather, not unfrequently cuts short the cherry crop by preventing proper setting. There is, however, no general complaint of poor crops through self-sterility. In fact from the behavior of perfectly isolated trees in all parts of the State it would be premised that the cherry is most nearly self-fertile of all tree-fruits.
Yet there may be orchards or seasons in which cross-pollination cuts a figure, for Gardner[54], of the Oregon Station, found in experiments carried on by him in various parts of Oregon that many varieties of Sweet Cherries in the Pacific Coast environment are self-sterile. The work seems to have been very carefully done and the conclusions are worth reprinting in full, bearing in mind that they would be much modified under New York conditions. Gardener found:
"1. All the varieties of the Sweet Cherry tested are self-sterile. This self-sterility is in no case due to a lack of germinability of the pollen produced. On the other hand, the pollen of each of the varieties studied is capable of producing a set of fruit on the variety or varieties with which it is inter-fertile. The list includes Bing, Black Republican, Black Tartarian, Coe, Early Purple, Elton, Knight, Lambert, Major Francis, May Duke, Napoleon, Rockport, Waterhouse, Willamette, Windsor, Wood.
"2. Certain of these varieties—Bing, Lambert, and Napoleon are mentioned especially—are inter-sterile. Mixed plantings of these three varieties cannot be expected to set fruit unless the trees are within the range of influence of some other variety or varieties that are inter-fertile with them.
"3. Among those studied, Black Republican, Black Tartarian, and Waterhouse seem to be the most efficient pollenizers for this group of varieties.
"4. Other good pollenizers that may be mentioned are: Elton, Wood, Coe, Major Francis, Early Purple. These, however, proved somewhat variable in their pollenizing abilities.
"5. Some of the seedling trees found in and about cherry orchards are efficient pollenizers for the three varieties—Bing, Lambert, Napoleon. Probably many of these seedling trees are efficient pollenizers, though the value of any particular seedling can be determined only by experiment or very careful observation.
"6. At least some members of the Duke group of cherries are capable of pollinating some of the Bigarreaus.
"7. At least some of the varieties of the Sour Cherry (P. cerasus) are capable of pollinating some of the Bigarreaus.
"8. Inter-sterility of Sweet Cherry varieties is apparently not correlated with their closeness of relationship.
"9. The ability of a variety of cherry to set fruit is not entirely dependent upon the kind of pollen available. Environmental factors are important."
It is doubtful if New York cherry-growers will need to pay much attention to cross-pollination but, in case cherry trees are not setting full crops, and for no other apparent reason, the fertility of the blossoms may well receive attention. Should varieties be found self-sterile, sorts must be chosen which come into blossom at the same time, in which case the preceding table shows the sorts which bloom together or nearly enough so to make cross-pollination possible.