December is the quiet month of the year when much of the tidying up has been completed, the plants are mostly dormant and there are few flowers about. So make the most of form and colour on individual plants and enjoy what nature has to offer.
I got some Teasel plants from a friend who warned me that they can seed everywhere, which they do but I only let a few grow. They get to 2m tall and have lovely seed heads which are especially beautiful when touched with frost (see photo). Leave over winter and many more will self seed the next year then flower the following year.
For scent in sheltered spots against a wall in well drained soil, I would grow the Wintersweet or Chimonanthus praecox. This tall shrub (3m or more) has large leaves which drop in autumn. A few weeks later the waxy, pale yellow or cream flowers appear on the branches and the scent is rich like lemon and ginger or mulled wine! Follow on winter scent in February can come from evergreen Sarcococca (Winter Box) planted around the base.
Colour in winter can be seen on the Skimmia Rubella which has red heads of budding flowers which open to white in spring. It is said to have scented flowers too but it is not a scent I can smell! If you plant it under or near a red berried variegated Ilex or Holly it will give a very Christmassy colour scheme. Ilex aquifolium Madame Briot has green leaves edged with pale yellow.
Front of border, have a selection of Heuchera with their colourful foliage which will last into winter and looks beautiful with frosted foliage. Mix in some Primula with them as they flower on an off throughout winter, in mild temperatures.
Work to do in the garden this month is limited outside. You can continue to dig over borders or vegetable plots to remove weeds. I would also mulch with a layer or well rotted manure afterwards. Keep off frozen soil as it will be too hard to dig! You can also continue to prune any deciduous shrubs that need a tidy up.
If you have ordered bare rooted shrubs, hedging, fruit or trees do make sure you have prepared the planting area in advance by digging out all weeds and adding well rotted manure or other organic matter to the soil. Plant when the ground is not frozen.