Hi, 

This looks like gummosis likely due to a boring insect. Stone fruit trees are susceptible to borers and since you started these trees from grocery store fruit, it would be difficult to determine what they're parent plants may be. Especially with fruit trees and their many different cultivars that have been bread for disease resistance, growth habit, heat tolerance etc, growing from the pit they will be unlikely to fruit. Usually plant breeders and fruit tree growers will graft fruit trees so they know what root stock and top growth they are getting. Growing from the pit is a fun experiment but could be why they are getting borers as the trees may be stressed from being 'not true to form' plants. 

You can read more about peach tree borers on our webpage and ways to manage them: https://extension.umd.edu/resource/peach-cherry-plum-and-nectarine-insect-pests

Let us know if you have further questions. 

Emily 

Hello William,

The genetics of a seed is split between its two parents, and if one parent is unknown (open-pollinated) then you won't know what traits it carries. The genetic material from the tree bearing the seed (fruit) is from the part of the tree carrying that fruit, so that would be the top growth (scion) and not the rootstock unless it had suckered and that growth had fruited. (Graft points on fruit trees are trunk-to-root, not trunk-to-canopy.) The scion of desirable cultivars of fruit trees (and many other instances, like many ornamental trees) is selected for specific traits like productivity (yield) and fruit quality and disease resistance, where the rootstock is chosen based on other traits, like cold hardiness, its own disease resistance, and importantly, dwarfing ability to keep the canopy smaller than its normal size so fruits can be more easily harvested and trees will fit into more confined spaces. (Dwarf trees still produce a proportionately normal amount of fruit in relation to their stature, nor are the fruits smaller than a non-dwarf variety.) Since fruit trees are not grown from seed, it's likely a seed-grown specimen will bear fruit that is of poorer quality or low-yield, more vulnerable to disease, and not dwarf, though it's pot-luck with what genetics you get when trying such an experiment. Seed-grown fruit trees also tend to take a few years longer than grafted trees to reach an age mature enough to start fruiting.

Miri

You're welcome!