I just put all of the pictures up first, since basically then have nothing to do with the text today, though I guess the others from the past 4 days didn't really either. Just wanted to give you some idea of the variety of types and colors that are out there. Here is some history. As you will see, these are just a miniscule glimpse into the world of the rhododendrons.
Until fairly recently, rhododendrons were considered to be more appropriate for large estates and the prices reflected that. Plant discoveries in Asia near the end of the 19th century and the resulting hybrids opened up the possibility that ordinary gardeners could also grow them. The British were at the forefront of this change. Species were brought from China, Japan and the fringes of the Arctic Circle, from the Himalayas, Assam and Burma.
At the time of King Charles II, only one rhododendron was in cultivation, R. hirsutum, which had been introduced into England in 1656 from the Alps, and was know as the Alpine Rose.
By 1800, there were still only 12 species known. In the middle of the 1800s, Sir Joseph Hooker brought back 5 new species from the Himalayas and Robert Fortune sent back many plants from China.
By 1900 some 300 species had come to be known, but the interior of China had yet to be explored. A group of French Catholic missionaries were the first to discover what was waiting there, but Dr. Ernest Wilson made the first systematic exploration at the turn of the 19th century. From there onwards, a flood of new discoveries poured in from successive expeditions of a great company of collectors traveling through the mountains of Asia, often among hostile inhabitants, across trackless and precipitous hills, threatened by fierce storms and floods. George Forrest and Reginald Farrer died on their expedition, but their work was carried on by Captain F. Kingdon-Ward and Dr. J.F. Rock (of peony fame) and many others. This was the golden age of plant hunting in China.
Their exploration brought us new colors, new forms and a season of flowering that extended to half a year. There were dwarf plants, suitable for rock gardens, some that reached 40 feet tall, and one with leaves a yard long.
The number of known species had thus swollen to about a thousand; no doubt yet more would have been discovered if China, on becoming Communist, had not closed its borders to plant explorers (and everyone else) from the west. (my reference, printed over 50 years ago before the re-opening of the Chinese border, does not cover any newer discoveries)
We shouldn't forget, thought, that there are also rhododendrons that are native to North America, and those were also being imported into England in the 17th century. It is thought that the first deliberate hybrid was made by Michael Waterer in 1810 when he crossed Rhododendron maximum, which is native even into Canada, and Rhododendron catawbiense, from the western mountains of North Carolina. At least at the time of this book, the original specimen was still alive at Knapp Hill Nursery which he had founded. Many other hybrids followed, with the emphasis on developing plants that would be hardy in cold climates.
By the early 1900s, rhododendrons had become so easy to grow and so popular, they started replacing plants that had been popular in Victorian gardens, Laurels and Aucubas.
If you garden in northern climates, probably the most important species to you will be Rhododendron yakusimanum, originally found on the small island of Yakushima in the China Sea. Rhododendrons with this species in their genetic makeup are commonly called 'Yaks'. It is rated to survive to -5 degrees F., but it is known to survive much lower temperatures than that. For that reason, it has been used extensively in breeding for cold hardy plants. If you're looking for cold hardy rhododendrons, some varieties to look for might be Yaku Angel, Silver Bear, and Mist Maiden. Lots of them will start with 'Yaku'.
There are 2 nurseries that I would recommend highly for rhododendrons; Greer Gardens http://www.greergardens.com , whose owner Harold Greer, wrote an excellent book of the subject of rhododendrons with descriptions of hundreds of available rhododendrons and azaleas and plenty of pictures, and Rare Find Nursery http://www.rarefindnursery.com which has just a huge selection.
Enough on rhododendrons. I'll be back next week with something new. Keep warm.