Gabe15

It really depends on what plants you are considering. Different size plants will require different size pots to get full size in. They also might get larger than you can really handle being in a greenhouse, or moving them between outdoors and the greenhouse.

You don't really need full size plants to make crosses, you just need them to flower, and you don't need big pots to get them to the flower. In a smaller container, they will fruit smaller, which can be a good thing. So, the size of the pot doesn't really have to be as big as possible, just enough to not cramp them so much they will have greatly delayed flowering. What size is ideal for each variety you are working with will be revealed by experimentation, but I would guess 500L is plenty for whatever you are working with, and you might consider experimenting with something even smaller, say around 100-200L to stunt the plants so they are smaller and easier to move around.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.