Winter is a great time to catch up on how your year went in your garden. If you do not keep a garden journal then I suggest you start. My personal favorite journal to use is a little yellow rite in the rain all-weather journal. I was first given one as an intern at Brooklyn Botanical Garden and have carried the habit of using one with me since.
I like to keep track of the weather temperature, how much rain we get and if we are having clear skies or have seen a lot of cloud. Watering, pruning and feeding schedules are tracked as well as plants of course. I keep note of what plants worked well and maybe what did not go as well as expected and what specific issues a plant faced. If I am lucky enough to spot any beneficial wildlife and insects or also any harmful pests they will go in my notes also.
It is nice to sit on cold days like today and go over these notes to come up with ideas and plans for spring. I review garden magazines and get excited for plants to try out next year.
There are of course some jobs which can still be done, its good to put some compost and mulch on your beds if you have not already. It's a perfect time of year to gather up your leaves and if you have the time and space make a nice leaf mold I highly recommended it. I would at very least suggest raking all leaves off your lawn and spread around your garden beds. This will greatly reduce the number of bald spots in your lawn next year. All garden furniture can be secured and stored for winter, gardening tools such as lawnmowers can be drained of gas and sharpened, garden sheers, pruners and any other hand tools will benefit from a good cleaning sharpening and being stored correctly over winter.
It is still too early to start winter pruning trees, with temperatures fluctuating still most trees and shrubs will not have gone fully dormant just yet. This is a job best saved for later in winter especially with the milder winters we have been getting in NY & NJ zones 7a & 7b.
I have had people ask me when is the best time to cut back their perennials, and this can be more of a personal preference for the garden owner. Most perennials would be quiet fine to be cutback now. I would make an exception to that for grasses where the crown will benefit from the extra protection of not being cut back over winter. Personally, however, I would make the case for all perennials being left up over winter, as was the case on The High line when I worked there. Not only do these plants offer fantastic winter interest in the shapes and textures and varied winter colors, but they also offer a good contrast against trees such as Betula populifolia ( grey birch ).
The final consideration to be made and possibly the most important is, plants provide habitat for a lot of bugs and different nesting creatures that we must coexist with. Some of these insects and creatures are vital to the over all health of your plants.They can be beneficial in helping with the control of pests or help out with pollination. Because of this I would never personally cutback anything until spring unless a client specifically asked me too.
Lastly I encourage you to take out your favorite gardening books and magazines, catch up on some of your favorite gardening shows ( Gardeners World is a personal favorite ) and start planning for next year. Spring 2020 will be here before you know it!