One of my favourites is the winter flowering cherry. There are two varieties; Prunus x subhirtella "Autumnalis" with white blossom and "Autumnalis Rosea" which is a delicate shell-pink. They will tolerate most soils as long as they are not waterlogged and any aspect. Growing around 6m tall, with a relatively light canopy and pollution tolerant they are a perfect choice for city gardens.
At a time when most trees are bare, their branches tantalise with a generous sprinkling of tight buds which gradually open to delicate flowers. Initial flurries of blossom appear in late November and will carry on right through to March. They don't produce any fruit but do have good Autumn colours, soft shades of orange-yellow.
Having fallen in love with our first tree, we now have three "Autumnalis Rosea" in our garden and all are currently full of blossom. In Spring I prefer the purity and freshness of white blossom but the pink seems more cheerful at this time of year and stands out well against grey winter skies.