I got several comments about the camellia photo in the last set, and a few emails, as well, so here are my comments/responses to all (I think.)
I have to say I don't know the particular cultivar for the white camellia in the photo. It predates me in the garden at "The Big House," but I would venture to say is fairly common, since there is a huge swath of them (perhaps 50 shrubs). This particular bloom is in complete shade, at the base of a yoshino cherry. What I find interesting with this particular camellia is that it does so well under the cherries. Because the cherries are "Mr Big House's" favorite tree in the garden (and they put on an incredible show in early spring), we tend to add a little extra lime to our naturally acidic soil. The conflict exists in that the camellias really prefer an acidic soil, so in this particular area they don't always do so well. I will try to dig around at the base of these plants and see if I can locate an old tag from when they were planted, but it's 26 degrees at the moment in north-metro Atlanta, so that isn't probably going to happen in the next day or so!
A bright white camellia that I personally love is Nuccio's Gem. It is as pure white as a gardenia, and is incredible against its dark green glossy foliage. We have it growing on a north-facing wall, but it is up against the brick wall of the house, so it tends to stay a little warmer. (Do a search of "Nuccio's Gem" on this blog for a photo of it blooming last year).
For those readers who live in the northern part of the US, I can't honestly offer advice about which are the cold-hardiest. I would defer to Michael, who pointed out in a comment to the last post that the New York Botanical Garden has several that tolerate NY winters. I never grew them prior to my move south. I will say that I have a hedge of "Winter's Star" at the Big House that is very cold hardy (down to about 20 degrees, at least), and "Winter's Snowman" in the Stepchild Garden. Both are hybrids that are also growing in full sun, so they are definitely heat and humidity tolerant, as well!
Lastly, if you are new to camellia-growing, it's important to point out that they are like hydrangeas, in that there are several different forms with completely different growing patterns, likes and dislikes. Do some research before choosing one, since there are literally dozens if not hundreds. My personal opinion is that if you are looking for a classic elegant Camellia with the dark glossy leaves and big blooms, you're probably looking for C. japonica. That being said, I will tell you that I have japonicas, Sasanquas and hybrids in the Stepchild garden, and love them all for different reasons. Again like hydrangeas, planting the different varieties give a much longer bloom season.
And for those who have "zone envy" for the South, just know that I would kill to have my parents' 100-foot-long hedge of lilacs that grow like weeds in their New Hampshire garden. And don't even get me started about yew hedges......