The name simply means native to Japan. Japonicas are well known for their beautiful glossy foliage but what is sometimes forgotten is the variety of sizes and shapes between each cultivar. Leaves can vary from small to very large, narrow to rounded and there is even a "fishtail" leaf, which divides at the tip. Japonicas flower from late winter to May and are famous for their bold red flowers but this is not the only colour on the japonica's palette. The colours actually range from pure white, through the pinks and on to the richest reds. japonicas will form a good shaped shrub and can eventually become a tree, though again there is no fixed shape for these cultivars and each plant should be looked at for it's own merits. Some are vigorous and compact, others tall-growing and pendulous.
The williamsii hybrids originate from the cross of C. saluenensis x C. japonica produced by J C Williams in the early 1930s. With their smaller tougher leaves, they are remarkably hardy even in the most extreme British weather. Williamsii hybrids produce an abundance of flowers, even in areas of low light and despite harsh conditions, and are more successful than C. japonica in the North. They are also popular as their flowers tend to drop neatly as soon as they are over unlike some other Camellias which need dead-heading.
Sasanquas are the beautiful autumn flowering Camellias. Their flowers are never very big and are mostly single or semi-double. They come in shades of pink and white, there are no strong reds and most are slightly scented. Sasanquas are more informally shaped than the Japonicas but are faster growing. It isn't necessary to prune a sasanqua unless you want to create a formal clipped hedge, in which case it is best to prune after the flowers are over. Sasanquas can create a superb dense hedge that will flower every autumn. After the flowers have finished the plant produces interesting shiny black seeds (in Japan these are used to make Camellia oil and beads). The added advantage of the sasanqua is that they flower best in full sunshine, while other Camellias prefer some shade.
The original reticulata varieties came from temple garden in china, where they have ben tender and revered for centuries. They are typically tall upright shurbs with bold, pointer foliage and very large richly coloured flowers. Unfortunetely they are not seen at their best in the open in the SE England, but they have been used to breed a number which are very garden-worthy and hardy, capable of producing rich colours and magnificent flowers. The largest do best when sheltered from the coldest winds by a fence, shubbery or wall
There are many Camellias species in the wild in Asia and they typically have large numbers of very small white single flowers with a special cham all of their own. They are perhaps best compared with the wild dog rose with its 5 petals and golden stemans. Their twigs are thin and bendy, so the plants are much less stiff, and their leaves are correspondingly more delicate.