Here is how my varieties look so far this year. The numbers are my guess, and the designations are (triploid) for triploid and (d) for diploid, based on my memory. I might be assuming some as diploid for lack of better information. I spell out "triploid" to make it stand out better. I might be missing some.
North Pole (d)
Golden Sentinel (d)
Many open flowers, 25% to 50%.
Queen Cox (d)
|Golden Sentinel. 4.27.17|
Ornamental Crab Prairie Fire (d?)
Airlie Red Flesh (d)
Sutton's Beauty (d)
Buds present but none open yet.
|North Pole. 4.27.17|
|Prairie Fire Ornamental Crab. 4.27.17|
|Airlie Red Flesh. 4.27.17|
|Queen Cox. 4.27.17|
|Liberty on M27. 4.27.17|
I don't know if Prairie Fire can serve as a pollinator. The tiny crab apples are worthless, but it's a beautiful tree when in full bloom.
Some of these are 1-year old growth from grafts, such as Airlie Red Flesh - covered with flower clusters (also sold under trademark name "Hidden Rose"), Baldwin with lots of flowers, and one flower cluster at end of stem on Newtown Pippin (not open yet).
With daily rain and chill, I feel some concern that none of them will pollinate. Considering how early Gravenstein was, I cut off a stem of flowers from North Pole and left it in the Gravenstein tree. I don't know if that will help.