I just discovered that my 7 year old Red Haven peach has rooted itself from above the graft line. How bad is this? I know if this were an apple it would take away the important traits of its rootstock. but in a peach is it as important to keep the grafted wood from rooting?
Unless you had it on some dwarfing rootstock, it won’t matter if the scion rooted. Most peaches are on full vigor stocks anyway (Lovell, Bailey, Halford, Guardian, ect.)
Some peaches are grafted on plum rootstocks, so they can tolerate wetter soil. In that case a rooted peach scion could potentially cause problems down the road in an unusually wet year.
To add to Olpea’s remarks, the planting instruction that came with my peach trees from Grandpa’s Orchard say in part: "…You should always try to plant the bud union one to two inches below ground level for almost every standard or seedling budded rootstock or fruit tree. Covering the bud union helps to reduce the amount of “suckering” that can occur from seedling rootstocks. Since the variety is budded onto a standard or seedling rootstock, it will grow as if it were on its own roots and can reach its natural, potential full size. Even if there is “scion rooting” the ultimate size of the tree is not affected and remains the same.
Dwarf, Semi-Dwarf, certain other size control, or precocious rootstocks: In order to not loose the beneficial effect of these special rootstocks, which you usually pay more money for, it is important to not plant too deep.