I profess no particular expertise or intimate knowledge to encourage spring and autumn flowering camellias, though I happily tout success with both with several growing to ten feet and taller with long periods of bloom. This is a small collection of no more than ten or twelve species and hybrids, but all seem quite happy, and in recent years all have flowered splendidly in part sun and shade.
Certainly, there have been times when temperatures falling below zero (Fahrenheit) have frozen fat buds and ruined the spring bloom, but with well established plants and milder recent winters flowering has been dependable. No matter the cold, foliage of spring or autumn flowering camellias has not been harmed in this northwestern Virginia garden.
When first planting camellias, I cautiously opted for only the hardiest autumn flowering hybrids, and while I’ve been encouraged to stretch the limits a bit, space is now limited. Yes, it’s likely I’ll add a few more, but space is tight and I’ve seen first hand that camellias grow quite large, so there will be no more than a few that must find the sunniest spots in areas that are likely to be a bit too shaded. I’ve had my eye on several Sasanqua camellias, but these are marginally cold hardy, and I am not yet convinced that temperatures to zero and below are gone forever.
Areas with sufficient sunlight are limited, and camellias stretched into more shaded spots display many fewer flowers. The ideal seems to be a few hours break from the afternoon sun, and most in the garden in this situation are autumn flowering hybrids, the Winter series developed for cold hardiness since these are the most exposed.
The autumn bloom, that dependably begins in October, extends into December, and without extreme temperatures, into January. In a very mild winter, a ‘Winter’s Star’ and ‘Winter’s Interlude’ that are more shaded and often tardy in flowering, will bloom through all but the coldest periods of January and February so that there is only a short break before spring bloomers (Camellia japonica) begin to flower.
Ramblin' through Dave's Garden 
Beautiful clicks
While growing camellias, which were almost exclusively Camellia japonica and Camellia sasanqua, with only a few Camallia reticulata, we did nothing to promote bloom. They just did so regardless of our work to promote vegetative growth. We grew only nursery stock, so bloom was not as important as it was after the material was established into landscape situations. However, those who happened to install the material into landscapes during or immediately prior to bloom appreciated it. Prior to bloom, well budded plants were desirable for retain nurseries.
If we ever go back to typical zone 6b/7a winters the flower buds on Camellia japonica are often damaged. This temperature is too cold for dependable survival of sasanqua camellias.
Some of the most prolific Camellia sasanqua that I have ever seen are in the Los Angeles region (although closer to the coast than Nuccio’s Nursery, which is in Altadena). Although bloom is very impressive, it is not as reliably seasonable as it here. It can be quite early or quite late. It is not a problem for those who are not concerned about when they bloom, but makes it difficult for those who like to schedule phases of bloom in their gardens.