Summary: that will flower in mild spells from November to March is the Iris unguicularis Mary Barnard This iris has pretty delicate scented flowers of purple with interesting patterned coloured veins in the centre of yellow white and black and it flowers amongst grass like foliage If you want a winter flowering tree then you could go for the Prunus x subhirtella Autumnalis Rosea
Image Dimensions: 300 x 284
Image originally found here.