We are in Anchorage, Alaska, traditionally Zone 3. Probably due to global warming and/or urban heat island effect, we have not had any zone 3 weather since 1990, and the last zone 4a temperatures were in 1996. I think we can gamble on being zone 4 from here on out.

Local nurseries stock a full variety of cold-hardy sour cherries, including the Evans cherry from Canada, but no sweet cherries. The Regina cherry seems to be the only sweet cherry generally agreed to be hardy to zone 4. It requires a pollinizer, however. Can a sour cherry effectively cross pollinate a sweet cherry such as the Regina? Or should we take a chance on one of the other sweet cherries which might be hardy to zone 4 or maybe only to zone 5, depending on which Web site I pull up?

Similarly, the Mount Royal plum, commonly said to be the hardiest European plum, and partially self-fertile. To maximize yields on the Mount Royal, what would be recommended as a pollinizer in a zone 4 climate? The Canadian Brookred and Pembina plum varieties appear ideal, but getting fruit trees shipped into the U.S. seems nigh unto impossible. Apparently someone had to actually smuggle the Evans cherry across the border.