Fruit trees unproductive, shooting off lots of suckers/offsprings

Question

So I have this huge garden at the edge of a forest, on a hilly landscape, left over from my grandparents. It's been unmaintained for 5-10 years now. There used to some great grafted fruit trees with significant yearly fruit production . But since it's been unmaintained a lot of wild trees from the forest have invaded the garden ( accacia, oak etc.). Most fruit trees have almost suffocated, have lost most access to light, some died. I cleared some of the wild trees last year, but here's the issue.

A sour cherry and some plum trees are showing this weird (in my view) behavior. They have been shooting tens of offsprings for the past few years, i assume from an underground root network. Some are quite mature, spread over an area of 50-100m2 around the original trees. However, they are barely producing anything, although they do have quite a bit of flowers. Most fruits just dry out and fall off. Now I'm assuming this is because the tree has switch its reproductive strategy, so that it's no longer investing in fruits? Does that make sense.

A couple of years ago, one such offspring was moved to another garden, 100km away, and it's been very productive. However, these two "forests" of sour cherries and plum trees are producing almost nothing, less than that 1 moved offspring.

I know it's not the soil, the soil was perfectly good for decades. Yes, the trees have grown a bit too close to each other, so they are fighting for light between themselves, the plum trees mostly only have leaves at the top.

Is there anything I can do to obtain production out of them again? Only by digging them out and moving them ? Some are too large/old for this already.

Thanks.

Answer 1

You say that the trees are grafted, right? If so, then the trees coming up from below ground level are actually being produced by the rootstock and not the scion. This could be caused by competition between the scion and the invading trees from the forest - and, now, with competition from the rootstock's own offspring.

But then, you say one of the "offspring" (presumably from the rootstock) was moved and is productive.

So - if we assume that the successful offspring was a plum, we may also assume that at least one plum is not grafted and is spreading, in plumly fashion, rhizomatously. This means that the successful offspring was actually cut out of a plum that is not producing due to competition.

In my mind, that's a lot of assumptions, so I may be completely wrong here.

To get everything back to production, I would recommend that you cut down all young growth (less than 5 years old, at least) between the trees. If you can see the established trees, you could remove all growth between them. Do not treat the stumps unless they're non-fruit-tree stumps - this would injure and/or probably kill the parent trees. Next, prune out all deadwood from the older trees. You may also want to prune them at least a little for production at this time. The next year, see what happens and/or complete the production pruning.