Anyone have much experience in propagating root stocks?

I planted some root stocks to be kept as root stock sources so I can continue to expand my orchard for the rest of my life.

I'm particularly interested in

Colt Cherry
M7 Apple
St. Julian-A Plum

What's the best way to propagate each of these? I've heard M7 apple suckers easily (that's a good thing). I haven't been able to find anything about propagating Colt cherry or St. Julian-A plum.

look into "stooling" rootstocks, its where you cut the tree to the ground while dormant, then as new shoots come up in spring, cover them with some kind of easily rooted-into medium, and the new shoots will root into aforementioned medium.

I have a Howard Miracle plum on St. Julian and it suckers. I've separated a couple to use as root stocks and have 2 or 3 more now that I could probably use.

One I grafted last spring with a damson and a Japanese plum and they seem to be doing well.

I have a Northern Spy apple on M7 and it regularly gives me a new rootstock, about one a year. I don't get complaining about suckers like that. I call it free rootstock. I'm going to have to do some guerrilla gardening here pretty soon.
John S
PDX OR

I've had good luck with the stooling method of rootstock propagation. One tip I learned from a local commercial rootstock farm is to plant the mother plant at a 45 degree angle. This increases the surface area of the mother plant when pruned back to the ground so you will get more shoots/rootstocks from it.

I've collected a number of suckers with their roots from my existing apples trees (on M7) for the purpose of creating new rootstocks. It helps to pile up some compost on one side of the trunk temporarily to encourage sucker growth. Once a cluster of suckers is a few inches tall I carefully cut them out with as many roots as possible and replant together in a pot. You can try to separate and replant then, or in my case I replanted the cluster in a pot for a season and then separated and repotted each individually the following season when they were larger and stronger. I now have 20-30 healthy individual rootstocks to use.