I use a pretty low management approach to growing my peach seedling rootstocks. I gather pits by stepping on drops. I put them in a bucket. Take them over to the row where I want the rootstocks. Use a shovel to make a crack. Drop the pits in the crack and push it closed w/ my foot. They germinate following spring. Sometimes I take random peach sprouts from under peach trees and move them to my seedling area for future budding.
I have read pits from later varieties have better germination, in some research paper. I have noticed in a very cursory way that I see few peach seedlings under early varieties vs. late ones.
Also read Redhaven pits allowed to grow out (ungrafted) will frequently produce a smaller tree (This was how Compact Redhaven [which I no longer think is extant] was created.)
I doubt the assertion, “Grafting an early cultivar on late rootstock or vis-a-vis can have undesirable results” at least as it relates to peach seedling rootstocks.
Halford cling is often used as a peach rootstock in the Midwest and south. It’s a very late peach, but is a dependable rootstock for any peach. I’ve not yet noticed any difference in various peach seedlings I use for rootstocks, regardless of what varieties are grown on them. But if there is some research which suggests otherwise, I’d like to read it.
I suspect the issues w/ peach on Citation result from Citation being a plum rootstock. Plum rootstocks tend to have more issues when used for peaches.
I’ve pulled up lots of peach trees and never seen a taproot yet. Sometimes I see new peach trees with a sort of tap root, but it really doesn’t keep growing down like a true tap root (i.e. oak). Peach trees, when they develop, grow a goose foot root system. In dry areas w/ a low water table, I suppose it’s possible for peaches to develop a tap root, but all the photos I’ve seen from pulled up peaches (in other parts of the country) show a goose foot root.
I have a friend who purchased Lovell seed the last part of last winter to grow Lovell seedlings. He put them in the fridge for what we thought should be enough chill hours, but he didn’t get a single one to germinate this summer. We think he was a little short on chill hours, but we couldn’t find any research indicating how many chill hours Lovell seed requires. The seed was also dry when he purchased it, so I don’t know if that impacts germination or not. (I always plant my pits immediately in the ground before they dry out.)