I have an awful lot to learn about rock gardening, but do have some low-ish flowers blooming today. Zone 7 in Maryland is not generally known for its winter flowers, but I'll bet there are probably a few out there with which we could all "push our envelopes further." If anyone has any suggestions to add for clay-based soil in our zone to perk up our winters, would love to hear them. Also, wherever you live, would also love to see more posts and pics of December rock gardens.
I don't know if this one qualifies as a rock garden plant, but the whole plant is 24" high right now, with half-a-dozen flowering stalks to about 19" with blossoms clustered at the top: Helleborus x hybridus. This came to us as a random seedling from a local nursery, and none of the others in this batch start blooming from December into May as does this one. It's single, white with purple speckles toward the center and is unusually vigorous compared to the others. I hope everyone feels free to dmail me in May for seeds - fresh ones may germinate more easily.
Occasional blooms from Viola labradorica are appearing up and down a path along a yew hedge where they have self-sowed through a cream/green variegated vinca minor.
Viola odorata - a pink form whose parent came from Sorgina. Its normal blooming time is said to be between November and April and this is its first winter with us, so it will be interesting to see how it does during any warm spells. I had thought it would make a pretty edging to Begonia evansii (from Critterologist), but who knew what a thug that begonia could be with so little sun and water? When I move it next spring, perhaps it'll make more than 2 stalks of flowers this time next year.
Viola tricolor - it crossed all by itself with some pansies and has behaved differently from its more ordinary relatives around here in that it blooms longer through the entire summer, has a color range from pale blue/violet to very dark purple with cream, whiskered faces and no yellow; and varies a great deal in size and patterns (much to my delight).
Ordinarily, camellias are not known to be very bud-hardy around here, even though their roots may be cold-hardy. However, the National Arboretum bred some camellias that they named after various Native American tribes which are definitely bud hardy here and that bloom mainly in the fall - into December with us with 'Snow Flurry.' They shatter more easily and thus might not compete well with other kinds in a show, but nevertheless we are thrilled to have Snow Flurry's flowers in our garden this time of year.