January to March is the season for blood oranges. They can be sweet or tart, with hints of raspberry, deep orange to dark crimson and a lifesaver when other fruits are unavailable to brighten up winter dishes. In the UK you're likely to find three varieties, each with their own characteristics:

Tarocco: grown in the nutrient-rich soil around Mount Etna, Tarocco are sweet in flavour and have the highest vitamin C content of any Orange variety in the world.
Moro: from Siracusa in Sicily have the deepest colour, sometimes almost black, making them great for providing visual contrast to dishes.
Sanguinello: the Spanish Sanguinello is more sweet than the Moro and more deeply coloured than the Tarocco, so is a good all rounder for a variety of uses.

Whichever type you prefer, blood oranges can be used in sweet or savoury dishes as the flavouring for souffles, an accompaniment to seafood, part of a winter salad, a refreshing sorbet or, of course, a delicious cocktail. To get going, try this easy blood orange and lemon posset.