Tree Root Feeding in Winter?

Here in Western Washington we have mild winters. I have noticed that laurel that I put in larger pots in the fall, will have filled out the pot, with roots, by spring - so I conclude that the roots grow through the winter.
I have just transplanted some 15' tall Leyland Cypress and would like the roots to recover by next summer. I lost some from a spring transplanting, last summer, and conclude that the survival chances are far better when done in November, as they have the whole winter to grow new roots. Question:
What can I feed the roots, during the winter that might help them along? B1 stimulator or is that not to be done in the late fall? I assume that nitrogen is not to be given. How about phosphorous?
Thanks, RO
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I'd be careful feeding them anything. It sounds like root development hasn't been a problem so far. A small amount of bone meal, maybe.
As you've mentioned, don't transplant them in the spring.
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