Half of peach tree won't ripen.

Hi, I have three peach trees and only one of them does this.  It pretty much has a double trunk because the split is so low, but one arm of that bears lots of fruit that will not ripen.  The other arm bears a small amount of fruit that ripens normally.  Last year I thought it was because it was partially in the shade of a big old pine, but we took her down this year and it is the same.  Last year the fruit never ripened, remaining green until fall leaf drop.

I'm not at all an expert, hoping someone who is can weigh in, but it sounds to me like a grafting problem, where the side that won't ripen is probably from rootstock and the side that makes the ripening peaches is the grafted part. If that's the case, that part of the tree will probably always be like that. I know that this is a symptom of genetic mutation in other trees, but have never heard of it only being a part of a tree, so my guess is that the rootstock is growing there and effected.

Dem Krebs your right on. The one that doesn't ripen is from the hardier root stalk below the graft. The one that ripens is the grafted intended tree. I would heavily prune (40% ish) the one that doesn't ripen after leaf drop or late winter about a month before the buds swell. This will encourage the good tree to grow. Do this 2x and then the following year you should be able to remove it totally or just keep it very pruned back. Most of the tree's energy will go to the unwanted side if you let it.

Lorne Martin wrote: The one that doesn't ripen is from the hardier root stalk below the graft. The one that ripens is the grafted intended tree. I would heavily prune (40% ish) the one that doesn't ripen after leaf drop or late winter about a month before the buds swell. This will encourage the good tree to grow. Do this 2x and then the following year you should be able to remove it totally or just keep it very pruned back. Most of the tree's energy will go to the unwanted side if you let it.

Thank you so much!  That makes so much sense.  I will prune it back this winter.  

Keep a couple of small branches of the root stock to graft onto - you could start a multi variety tree - peaches and nectarines are compatible.

A free stone, clingstone, white, red, blood peach combination would be lovely.

Staggering the harvest time of the varieties too. I have many apples, peaches, plums and apricots that I have grown from pits/pips and it is great having lots of rootstocks to practise grafting on.