The winter garden is a great resource for photographers. The decaying flowerheads of shrubs such as Hydrangea and Viburnum, the skeletons of umbellifers (now the Apiaceae) and the occasional flowers of witch hazel and wintersweet offer a surprising range of plant material, often in striking juxtapositions.
Without the clothing of leaves, the plant structure is more apparent, and it is easier to get close to your subject for macro images. Light is often at low level, particularly on overcast days, but if you can get out on a bright day then you have the option of silhouetting twigs and flowerheads against a bright background.
Even better, in snow or heavy frost, the light will be reflected from beneath, giving a pearly glow to your subject. As a backdrop, snow can show up the tracery of plant skeletons to great effect.
These images were all taken in the depths of winter - some have been edited using the monochrome editing suite Silver Efex Pro, from Nix.