Rhododendron sinofalconeri SEH#229
From the mountains on either side of the Yunnan-Vietnam border comes the newly introduced, yellow-flowered, big-leaf Rhododendron sinofalconeri. This species has two very different forms from two separate areas, although each form more or less matches the type description. The form from southern Yunnan north of the Red River was first introduced into cultivation from a collection made in 1995 by Peter Cox and me in the Laojun Shan of southern Yunnan. Here they grew near the very top of the mountain where they formed a mini-forest of 20 to 25 ft. high trees. They probably originally grew to the very top of the mountain, much as they do on Fan Si Pan in northern Vietnam, but the Chinese had built a huge military installation there, and for this reason we were allowed very little time to have a look around! The plants from this region have a much more rounded leaf with a looser, paler indumentum, whereas the form from northern Vietnam south of the Red River has an elliptic leaf with a very tight, deeper-colored indumentum. This latter form of the species was introduced from the highest mountain in Vietnam (Fan Si Pan) by Keith Rushforth and Tom Hudson who found it in the early 1990s. The two populations are probably best referred to as races within a variable species, although they may eventually be split into two taxa.
I have seen both forms flowering at the same time in Tom Hudson’s garden, Tregrehan, in Cornwall, England, and they are very similar to one another. The many-flowered inflorescence (mid-spring) has blossoms that range from a pale creamy yellow to a very good deep yellow, typically with a small red blotch. In both flower and foliage, it matches up well against the popular big-leaf R. macabeanum but is substantially hardier than that widely grown species. R. sinofalconeri also has an amazingly strong and vigorous growth habit. Long internodal growth often more than one foot in length appears each year as the plants rocket into small trees. This exciting new addition to our gardens has been a best seller since it was first introduced and is one of the most highly recommended of the big-leaf rhododendrons.