Diane; I'll guess, after 8 years, there are no identifying tags left on any of the branches...? Can you tell if the original limbs have become the 'main limbs?' On these multi-grafted trees, a problem they have is that the budded varieties are all so low --- budded when the trees are very
small. Thus, if you loose any of those lower 'branches,' you've also lost the additional varieties... You did mention the only producing portion was from a low branch, could you have 'lost' the others? If so, you may be left with only two varieties; the 'base tree' -- usually a Golden Delicious
-- and whatever's actually producing fruit on that lone branch.
If the base variety (or tree) is a Gravenstein
, it requires two more sources for pollination. Gravenstein is also an early bloomer, so if your other orchard trees aren't blooming at the same time --- whoops --- you said it's not blooming at all... Hummm. Say, in the last 4 years, it hasn't bloomed at all? "Michigan Bulb
" sounds reputable (at least I've heard of them -- 'clear out here'), so I'll assume this tree wasn't simply a budded rootstock
...? And, if its original, or additional branches are 'still there,' there should be a lot more going on bloom-wise than you've described... I didn't notice your location, if it's central Canada
, there may be some temperature problems..?
If it's not producing, but is as lush as you describe, it sounds like the perfect candidate for Top-working!
That's dormant grafting another variety/s to its existing structure ... and it's not that
difficult. This remains open to further speculation ~ but these are my guesses, and suggestions