Three Dwarf Rhododendron Species
J. Harold Clarke
Perhaps few rhododendron fanciers begin their hobby by obtaining dwarf species plants. However - many who start out with the standard sized hybrids later become interested in species - and eventually in the dwarf forms. Some - who have very limited space for planting - may reach the dwarf species stage somewhat earlier.
I wish I could say that the species I am going to discuss would grow anywhere in the United States but that would be stretching it too far. Each one - however - does rate H-2 which means they can be grown over quite a wide range of climate.
The first of the three species is the dwarf form of R. keiskei. This is in the Triflorum series and the species is generally described as an open, leggy plant growing to 3 or 4 feet in 10 years, with clear lemon yellow flowers in April or May. However, the dwarf form, which has essentially identical leaf and flower characters, is rather rounded, spreading, quite compact, and might reach 18 inches in height in 10 years. A plant of this height would probably have a spread of 2 to 3 feet. Just when this dwarf mutant occurred in the British Isles I am not sure. I have grown something over 2,000 seedlings and only seven or eight were of the tall form. The rest were all dwarf and so uniform that one looking at them could not say whether they had been grown from cuttings or from seed.
They have bloomed with us in late March or early April, sometimes a little too early to escape spring frosts. However, at that season of the year, even a few days to enjoy the extremely free flowering little plants are certainly worthwhile. Where there is a little overhead protection, or where spring frosts are not extremely late, damage will be avoided.
The leaves, about 1½ to 2 inches long and somewhat convex, are a nice dark green in color and quite attractive the year around. I have not seen this plant damaged by winter cold and so cannot be sure just what its tolerance might be, although I would hardly expect it to be hardier than H-2. Our experience has been that seedlings in many cases will bloom when only two years old and practically all will bloom at three years. It does like a little shade.
In discussing the next species, R. keleticum, I would again like to refer to a particular form. This is the one known as Rock 58 and comes from the 1949 collection. Seedlings from this collection and their later offspring are perhaps not quite as uniform as the R. keiskei mentioned above. However, they are all quite low growing and spreading, with smaller leaves than the type. Thy give an impression of being extremely dwarf, among the smallest of the rhododendron species, a dwarf among the dwarfs. The leaves are bright green and about ½ inch long. The purple-crimson flowers stand up on erect stems, with the size and posture of a pansy flower.
The third species in this discussion is R. impeditum, probably one of the best known of the dwarf species as it has been grown and distributed both east and west. Some plants available are seedlings and others are grown from cuttings. The best stock would seem to be cutting propagated from some of the dwarfer, more compact seedlings which have flowers that are almost as blue as some of the so-called blue hybrids. The leaves are very small and the plants themselves will make rounded mounds about 1 foot tall in 10 years. The foliage is quite aromatic, a character quite common among the dwarf rhododendrons and yet all too little known and appreciated.
There are some dwarf rhododendron species that are said to be rather difficult to grow. Given minimum requirements, as understood to be necessary for all rhododendrons, these three miniatures will make themselves indispensable in your garden if conditions are at all favorable.
Such are the numbers and variation in the great group of rhododendron species that readers may well point out other combinations of dwarfs which they like just as well or possibly even better. For the present, however, I would nominate these as a very fine trio and welcome comments from any who have competitors to suggest.