In short, a successful graft is usually required. Fruit trees are grafted for a variety of reasons, and having lost the grafted top portion (called the scion wood), the benefits of the cultivar chosen will be lost, because the rootstock, while usually the same type of tree (peach in this case), will not have all of the same qualities to its canopy or fruit. Cultivars are selected to have specific, consistent traits like fruit flavor, quality, and abundance, the timing of ripening, resistance to certain pests or diseases, and hardiness to climate. Rootstocks are chosen with an overlapping list of qualities, such as resistance to certain pests or diseases, hardiness, and vigor (to better supply the canopy with resources for growth and fruiting). In addition, though, the rootstock is also chosen for its ability to dwarf (or not) the scion, which turns a full-size fruit tree that might reach two or three stories high ordinarily into a semi-dwarf or dwarf version, so its mature size is more manageable in terms of maintenance and ease of harvesting. (The tree overall will be smaller, not the individual fruits.)

All of this means that what you get from rootstock that sprouts after the top graft dies or breaks off will be pot-luck in terms of appealing qualities. It might be fine, or it might be a dud. While the new peach tree that grows from a rootstock may survive just fine, it won't necessarily have the same mature stature, fruit productivity, resistance level, or fruit quality that you chose in the original cultivar. Because of this, we recommend you replace a tree in this situation, but it's up to you. It may be a long time to wait to see if this winds-up being an acceptable tree, though, since grafted fruits also tend to have a head-start on fruiting age, and a tree on its own roots like this may take about 5 or more years (an educated guess) to begin fruiting, whereas fruit trees purchased already grafted and several years old will take less time to bear fruit.

If you would like general care information for peaches (if you haven't already found the page, that is), you can explore our Growing Stone Fruits in a Home Garden - Cherries, Peaches, Plums resource. Like most commonly-grown fruits, peaches are high-maintenance trees, and the yearly preventative sprays (organic or otherwise) that are often required to preserve tree health and fruit production also are easier to deal with if you have a known cultivar being grown, so it's more compact-growing than a non-grafted tree (and thus easier to spray the entire canopy) and so you know what its innate resistance level is to certain pests and/or diseases.

Miri

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