Garden Tasks for Winter (December - January)

Yes, there are many things to do to keep your garden beautiful, even in the winter.  

Preparations

• Dig organic matter into clay soils.
• Protect slightly tender perennials with straw or compost.
• Brush heavy snow off limbs to avoid snapping branches.

Planting

• Plant deciduous trees, shrubs, and hedges on dry, frost-free days, unless the soil is very wet.

Pruning

• Prune trees (except for plums and cherries) and wisteria.
• In late winter, coppice shrubs for special effects like color stems or foliage.
• In windy gardens, prune back the topgrowth of tall shrubs to prevent windrock.

Other Tasks

• Check stored dahlias, cannas, and gladioli, and remove any that show signs of rotting.
• Wrap up pots with bubble wrap and cover vulnerable plants with fleece if frost is forecast.
• Continue to take hardwood cuttings of deciduous shrubs.
• Take root cuttings of perennials.
• Continue to rake leaves off the lawn.
• Keep off lawns and soil when sodden or frozen.
• Check and repair garden tools.
• Begin making plans for next year's garden.

This list was found in Learn to Garden: A Practical Introduction to Gardening.  I did modify the list a little.