Now is the right but final time to fertilize fruit trees, grape vines, ornamental trees, etc. in northern climes.
Those roots are alive and hungry right now, storing up fat for Spring before they go dormant - even though the leaves are off. Just go easy with the fertilizer on the apple trees. Excess fertilizer encourages rusts. Too little is better than too much for them.
And, while we're at it, don't forget to try my trick. If you have good strong perennial herbs in pots (sage, marjoram, thyme), turn the pots upside down in the dirt for the winter. Odds are that they will spring back to life with a vengeance when global warming warms things up in April. Even it they don't, it will protect your pots from cracking from ice.
I bring my 3 year-old Rosemary bush indoors, but people might have better ideas for that. I like having it in the kitchen so I can run my hands though it. Makes me smell good. It barely survives the winter, but jumps back to life when we cut it back, and put it outdoors in April. My bro keeps his potted Rosemary in his garage, like some people do with their figs. (I let my fig rough it. I just throw a tarp over it and hope for the best.) One of these years, I will plant my Rosemary next to the foundation and cover it with a couple of layers of polyurethane for the winter. The goal would be to have a 6' Rosemary bush like they have at Oxford, and everywhere in Italy.
This guy in CA proudly posted his healthy but ramshackle Rosemary hedge:
