I Want To Grow An Apple Tree In A Container What Size Of A Container It Will Survive Winter

Question

we have a green house. floor is concrete we don’t want to have heating and cooling system

Answer 1

It depends upon whether you're growing the tree from a seed, a seedling, a cutting, or bare root stock. It also depends upon the variety of apple tree. Just remember that when you transplant a growing seedling, graduate only up a size or two at a time with your pot. If you're worried about the tree surviving the winter, you can wrap it - you're lucky to have a greenhouse! Here are a couple articles that should be helpful:
https://www.gardeningknowhow.com/edible/fruits/apples/container-grown-apple-trees.htm
https://www.gardeningknowhow.com/edible/fruits/fegen/winterizing-fruit-trees.htm