No and no.

Thank you Kudzu, I have learned alot from you. You are a wealth of knowledge. And I really appreciate that you share this with others.

The only qualification I'll put on this is that bamboo in the ground is always hardier than in a pot that has the same weather exposure...but that's a function of exposure, not an alteration in the inherent plant hardiness. If you are just moving a sensitive bamboo plant inside each winter you won't hurt it or its hardiness.

All true above, a hardy bamboo cannot permanently be altered in hardiness by being brought into a home or greenhouse. But remember, you can't take an otherwise cold hardy bamboo (or any plant for that matter) from a mild environment and put it outside suddenly as it has not been "hardened off"--so, in a sense, a plant's degree of cold hardiness DOES change--depending on the season of the year or growing conditions--(but not permanently). Something to think about when you're ready to move your "cold hardy" plants from the greenhouse. Good luck!

Thank You njoasis all very good points to consider. Or we could open up a can of worms and say that bamboos that are not mature are not as hardy as mature plants correct?

Mature plants are more hardy. This is probably due to at least two reasons: (1) The longer they have been in the ground, the more root established they are, (2) A mature bamboo grove almost creates its own microclimate (keeping minimum temps up and cutting down wind)--not to mention the increasing girth/insulation of the culms and rhizomes.