December in the English garden is usually relatively restful, so take advantage.
Cut back your borders. After a few hard frosts at the end of November and in early December, all the plants in the herbaceous and mixed borders will now have finally died back. Now its time to cut them back - remember to leave 10cm of plant showing. This helps in the Spring to show where plants should be coming through and identify any winter losses.
Deal with Dahlias. Dahlias will have truly blackened now, so cut them down. Some people like to lift them and dry the tubers out in the green house or dry store. However, if you live in the warmer end of the country, try tipping a hefty pile of old dry compost from summer pots onto the crowns to will protect them. Unless the bed is very waterlogged in Winter the success rate for the next year is much the same ... with a LOT less effort! Remember to level the mound down in the spring.
Leaves are nearly over. The only leaves left to fall are from a few old oak trees or maybe willows, so it's time to do the final leaf tidy from the grass and beds.
Winterise everything. Do the hard tidy of the garden now... put old pots, spray tools and wheelbarrows with WD40 and put them in the shed, put fuel additive in your lawn mower. Turn off water taps inside and leave then open or wrap them well with lagging. Mend wobbly fences and gates so the winter gales don't do more damage. Check if there are any branches likely to come down in a storm. A bit of work now can save you a lot of work later.
Decorate. Have a glass of mulled wine and decorate the garden with beautiful lights... the winter garden can look stunning at night time with a Christmassy display. Bring the outside in with some beautiful evergreen branches and holly.
Feed the birds. Don't forget to put out food for the birds and crack icy puddles. Get the children to mix lard and seeds together and chill the mix down for the birds to feed off. I use it as an excuse to empty out the larder of stale cereal and nuts. Make them into balls and hang from trees or use festively shaped cookie cutters. We used a well-known container for cat treats which rhymes with 'Friskers' and enjoyed the irony.