It’s that time of year. As temps heat up the BB stores are unloading plant material.
My local Walmart has Page Mandarins & Dancy Tangerines for $15! Meyer Lemon & Key Lime for $32. All originally $45.
I’m thinking about picking up a half dozen of the $15 ones for rootstock.
plus interstem.
You may even luck up on an unattractive apple tree at Walmart that got passed up throughout the spring. I did that several years ago on an old-fashioned Winesap which I was considering ordering off the internet. Just pruned it some to make it look better. Paid 12-$13. It’s one of my most consistent producing trees now.
Is that a good or bad thing…the interstem?
Would it make it less cold resistant? I could probably graft below into the rootstock. What you think?
Unknown, partly because the big box stores have a poor track record with plant labels.
These are labeled by the semi-local nursery they were grown. Hopefully that’s accurate 
i had a monty cherry like that. had 1 branch still alive. rest was dead. got it for $7. grew really quick once pruned and in ground.
If they are grafted there is hope.
What have seen from the big box stores is trees that are maybe properly labeled but with no rootstock information on the label. If that is okay with you buying it then it maybe a good deal. I was at Whole Foods a couple of years ago trying to find a particular item without having to buy it online and pay additional shipping. They actually had fruit trees there to buy. All they said was " apple" " peach" " plum" “cherry”. No description of what variety or size tree you were buying. Really odd to see.