Helleborus orientalis hybrids.
I grow every species of hellebore except one, so I also have some that bloom later in the season. Depending on the species and variety, hellebore blooms begin in November and continue into April. Many self-sow, so I now have thousands naturalized in the shade of my woods. Other green-flowered hellebores that bloom in winter are H. viridis, H. odorus, H. cyclophyllus, and H. multifidus.
The best-known hellebore, the Christmas rose (H. niger), blooms for me in late November. Because I have grown many seedlings from many different sources, I have some forms of H. niger that wait until March to bloom. Flowers vary in size and shape. Some are as large as 4 inches in diameter, while others are as small as an inch and a half across. H.n. ssp. macranthus, one of my favorites, holds its darkgreen leaves well above the flowers, hiding them, but also protecting them from extreme cold.
One of my favorite Helleborus orientalis hybrids, ‘Old Early Purple’, has dusky, dark-burgundy flowers visible in bud by Christmas and in bloom, usually, during January. A chance seedling of mine with pale-yellow flowers always opens a few wide-petaled blossoms just after the new year. On the wooded hillside, a dark, black-burgundy form from Elizabeth Lawrence’s garden begins to bloom in January.