Roots and Winter Protection

(photo of Phyllostachys aureosulcata 'Spectabilis')

Questions:
I have just moved to New York from Boston where I spent the last 4 years. I am originally from London, UK. We have an 18th floor north facing balcony which I am gradually buying plants for. Yesterday I bought a bamboo from 28th Street. I don’t know what species it is but it is tall and has yellow stems – maybe it is Phyllostachys aureosulcata? It is fantastically root bound. I have taken it out of its pot and am soaking its roots before repotting it tomorrow. I doubt if I’ll be able to make any headway unraveling the roots but I will try. If I have no luck is it OK to cut some of them to free them from going round and round for ever? Also will it need winter protection? I had some luck in Boston on a 28th floor balcony wrapping plants in burlap and Frost Protek.

I have also bought a Euonymus Manhatten which I am told needs more direct sunshine than I can provide, but I am ignoring this fact and hoping for the best. The balcony is very light. Will this need to be wrapped up when the temperature falls? Both are in 17” pots.

Answers:
Perhaps you have already dealt with the bamboo, but I am sure it is fine if you have to cut some of the roots that are too difficult to deal with. As with shoot pruning, root pruning is going to promote the growth of new root tissue so a little pruning is no problem. It is more important to train new roots downward into fresh soil than allowing the existing roots to potentially girdle the plant. Not to mention bamboo is such a tough and aggressive plant that I think you would have to cut off a ton of roots before you actually begin to stress the plant out. From my own experience I have lifted and divided a number of bamboo, complete with some root pruning, and they only seem to come back stronger and healthier. As for the winter protection, if you are familiar with the practice, then I would go ahead and do it to be safe. I hope that you do have Phyllostachys aureosulcata as it is more wind tolerant and more cold tolerant than Phyllostachys aurea. According to a few references here in the HSNY Library Phyllostachys aureosulcata is only hardy to zone 6 so there is no question the roots would appreciate a little extra protection.

As for the Manhattan euonymus, I would definitely wrap it. The larger foliage and softer stems (compared to the bamboo) will take more of a hit from the winter weather. According to references Euonymus kiautschovicus 'Manhattan' is only hardy to zone 6 as well, so again, the roots will appreciate the added insulation. As for the light issue, if the shrub drops some of its lower, internal leaves next year you will know it is most likely because the shrub is not getting enough sun. But I’m with you. Give it a shot and see what happens. I’ll keep my fingers crossed for you!