When the first flowers of this Eurasian wildflower, Adonis vernalis, open, it's as if the sun itself were rising from the soil of the garden. It has the same greenish-yellow color of the winter aconite, Eranthis hyemalis. The same color is seen in a very few daffodils, too. It's a yellow which has a glowing quality, soft and very appealing at this time of year, especially in dull weather. The blooms of this Adonis are not large, but it has no competition in the same color range at this time of year - although a particularly well-nourished dandelion, should it produce an early bloom, might be just as big, if not as subtle.
The Adonis is very tidy when it blooms, but it soon sprawls laterally: give it some room.
The propagation of this plant poses some challenges. Division works and is probably the easiest way. Seed is set freely, but there seems to be no agreement about how to get it to germinate. Evidently, even sowing freshly collected seed does not guarantee germination.
The plant shown in the image above is growing in one of the unprotected cold frames. These frames provide protection from browsing animals and bad weather, and on sunny days keep the temperature within the frame a bit above what prevails outside - but they do little if anything to moderate the temperature at night.