I would prune out anything growing into the center right away if I saw it.

I am not sure about the grafting / altered timing question, and I have often wondered about that myself. Good question.

Thanks dmtaylor, just pinched off the unwanted center growth.

Anyone know more about my scion question?

I have a 4 in 1 peach, nec, plum, and cherry and they all bloom with their species not together.

So...looking at my 4-1 pluot, I'm shocked at how long the new shoots are. The new green branches are already 2-3 feet long. Should I be thinking about stopping/cutting some of this growth or wait until summer to prune? I definitely want to keep this tree pretty short (under 7 feet).

Thanks!

You can prune vigorous stone fruits pretty much as often as you want. Some people prune 3 or 4 times a year or more, and with a smaller orchard you can prune very often. If you are experiencing a few feet of growth in just a month or two of time, personally I think it would be best to prune as early and often as you feel comfortable so that you can train your tree into whatever shape and size that you desire. Otherwise, you will indeed lose control. Don't be afraid. Be aggressive if your tree and your desires demand it. Your tree won't die from overpruning or anything like that. Although you will probably want to mulch and fertilize like a son of a gun.

Thanks! Should I wait until the new growth is done or should I go ahead and try and prune the thin green growth now? If the latter option, I think I'll need to get something sharper than what I have because I don't think I'll get a clean cut from the pruners I have right now on that new green growth.

I pinch out the tips and head back the new shoots as much and often as needed. So far I've pinched out some tips but haven't headed anything. I've got up to 2ft of new growth.