I am writing this in the middle of February. As yet it has been the mildest winter that I can remember. The grass has not stopped growing at all, and needs mowing again! Our willow tree leafed up in January, the hedgerows are breaking bud and the buds of so many plants are swelling that I won't list them.
The big worry is what happens if a cold snap occurs? Fortunately nature provides secondary buds on most plants, so that if Jack Frost kills off any new growth, they get another chance to shoot again when the weather picks up in the spring.
One notable exception to this are the Japanese Maples, they don't seem to get a second chance. If the new growth on a Maple is damaged by frost it is often unable to produce any more leaves and although it otherwise seems healthy no new leaves appear and the tree dies.
In most cases all that can be done if soft new growth gets frost damaged is to cut it off, although it can be left to the plant to sort it by itself if it does not irritate the eye.
On the positive side the roots of any new plantings will have been growing nearly all winter and should give a really good start to them. As will all the plants that are getting ready for spring if they don't get a chilly setback.