Schoolhouse European Plum

I got what was tagged as a School House plum from another company, not Raintree. After 5 years it has finally produced fruit that is about 1" in diameter, red in color and not a cling free. Could it be the root stalk that is growing? It remained in a bucket for 3 years before planting. It is a beautiful tree, but the fruit is bitter, very small, not yellow and not a cling fee. What is the size of your plants, as I get older, I don't have many years to wait for the fruit. I have a Shiro plum and an Italian plum close by. The Shiro was a 7 gallon and planted 2 years ago, and produce about 12 small plums this year, The Italian produces around 200 plums and is about 8 years old.

The best way to determine if the rootstock has taken over is to look at the base of the tree. You can follow shoots to the branch where the fruit is. Plum rootstock typically does not produce great tasting plums. You can reach out to your local Agriculture Extension office or your local Master Gardener group for more support. 

Would the Purple Gage European Plum and the SCHOOLHOUSE European plum work well together ?

Not as well as you'd hope. Gage plums bloom earlier and may not be able to fully cross pollinate with Schoolhouse as it blooms later in the season. Some years you will have overlap, some you may not.

Will any Asian plums cross-pollinate with this beauty? Such as Cocheco or Early Golden? Or does it require another European plum?

It will require another European plum.

Three questions 1. What is the final size (height and width) of this tree? 2. How close does the pollinators need to be? 3. We are just north of Seattle and have an established Italian prune tree. Will it be able to be the cross pollinator?

1. Mature height is 12-14' with a similar width (depending on pruning and form).
2. Pollinators need to be 100-200 feet and within line of sight for bees.
3. Your established prune plum should be fine for cross pollination.

Can Italian Plum be a pollinator for Schoolhouse plum?

Potentially yes, depending on your region. Italian plumns bloom late for a plum and can be inconsisent pollenizer.

Can the Pozegaca plum tree be a pollinizer for School House plum?

Yes it can!

WHERE CAN THE SCHOOLHOUSE PLUM, THE PLUM ITSELF BE PURCHASED? I LIVE IN MICHIGAN , I CAN BUY SEVERAL TYPES OF PLUMS BUT, THE SCHOOLHOUSE PLUM IS NOWHERE TO BE FOUND.

Many variaties of fruits are not grown on a large enough scale to be sold commerically. If you don't know a grower you would need to grow your own!