Answer: It is not easy to grow plants outside their natural temperature range. There is no way to overwinter it in the ground in Chicago that I know of (without building a heated greenhouse around it), it is only hardy to zone 7 and that is just too huge difference to overcome. The rule of thumb with tropicals is to protect them from temperatures below the 50 degree mark to avoid foliage damage. (Many tropicals also respond to the shortening day length by growing more slowly and sometimes dropping foliage.) In your area, that would mean a very short growing season unless you keep it in a container and drag it in and out in spring and fall -- in at night and out each day -- to try to maximize the sun it receives. This bamboo is evergreen when grown in warm climates but it does still lose some foliage periodically, as do other evergreens. If you brought it inside in early fall while the weather is still warm -- and before the Equinox so the days are still longer than the nights -- and provide supplemental light during the winter so its days are significantly brighter than normal, that might do the trick. You would also have to keep your indoor humidity higher than normal to help the foliage stay healthy. This does not really meet your goal of leaving it outside as long as possible. To do that, you would let it stay out until late fall then bring it into a sheltered place such as a garage where it could be cold but just above freezing all winter, then begin taking it outside on warm days in the spring (say temperatures in the 40's) so it can begin to wake up naturally with the season. Again, though, this would mean taking it inside and out daily in spring and fall to maximize the outdoor growing season for it. I'm sorry I don't have the perfect answer for you (unless you are willing to build that greenhouse and add supplemental lighting as well as heat it) but maybe this will give you some ideas.
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