Answer: Sweet cherries require cross pollination so you'll need at least two different varieties in order to have fruit on both. Your trees should be planted within 50' of one another. As for which ones pollinate which ones, choose cherries that flower at the same time and they should provide pollination for one another.
In order of flowering/ripening, here's the list from earliest to latest: Hartland,
Summit, Emperor Francis, Kristin, Ulster, Black Gold; Schmidt's Bigarreau, Lapins,
Hedelfingen, Royalton; Gold, Sweetheart, Hudson, Regina.
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