Eranthis

It is a wonderful sight in very early spring when these first come up and form a sea of yellow.   Even if you don’t have room for a sea of them, it is worth growing a few in the borders just to brighten up those dull winter days.  Each yellow flower is surrounded by a small green collar of finely divided leaves.  Fully hardy and tolerant of most conditions, these can be planted and then left to it.  Plant them 5cm (2") deep.