Rhododendron Notes
Our very early spring, in the Northwest, and long dry summer encouraged plants to grow and bud early. Many of the Lapponicum series never really stopped blooming and several bloomed quite heavily for the second time this fall. 'Elizabeth' bloomed off and on all summer. Buds on a number of the bigger growing hybrids and species are becoming quite large and might be damaged if we have a severe winter. Many plants are now in second growth after putting on an unusual long first growth.
Ten years ago this month is was decided to print a yearbook every three years. G. G. Nearing published his "Notes on the British Tour"; a most interesting report on the fine plants and gardens he saw while attending the International Rhododendron Conference in England. Dr. J. Harold Clarke and John Henny also reported on their experiences at the conference. These informative articles are well worth reading again.
- Bob Bovee
Astilbe , the hardy spirea, blooms in June and July when most of the Eastern rhododendrons have completed flowering. The white, pink or red flowers add color to the Rhododendron bed, and the fern-like leaves are attractive.
A ground cover, or edging, being used in the East is epimedium . Available through a number of sources, its heart-shaped leaves go no higher than five inches. In May and June, the dainty flowers bloom-white, yellow, lavender, or rosy red. In the winter, the plant disappears entirely, coming up again in the Spring heartier than ever. It will stand sun or shade, and multiplies well.
Spicebush, Lindera benzoin , is used in our garden as a backdrop for mucronulatum. Honey-yellow flowers in clusters are fragrant, and appear before the leaves. Bright red berries in the fall, further make the shrubs attractive.
Mr. Guy Nearing's Rhododendrons 'Ramapo' (violet), 'Wyanokie' (white), 'Lenape' (yellow) and 'Brandywine' (rose) are small-leaved, slow-growing, and compact plants. They are excellent in front of the larger-leaved Rhododendrons, and their color scope affords numerous possibilities for harmonious planting.
A newcomer to our garden two years ago, is Sweet Woodruff ( asperula odorata ), which came to me from the Jefferis' Media garden. It has more than proved itself. With dainty whorled leaves and slender creeping stems, it spreads quickly in shade, but has endeared itself to me in a garden just four years old, with almost no shade, by spreading moderately, and retaining a healthy, bright green color. It is low-growing - several inches in height - with small white flowers, and is fragrant in drying.
Juniperus chinensis Sargenti
will make a lovely blue-green mat on the ground. I use it as fore planting, and find that it strikes root at intervals, as it creeps over the ground.
- Betsi Kelius
In some parts of the South and in Southern California, azaleas have been rather freely grown in places where other rhododendrons were considered to be more-or-less out of the question. It seems quite logical that, in those areas, some of the dwarf rhododendrons which have so much in common with the azaleas, and require about the same cultural practices, should be starting to take hold. They go well with the modern small lot and low type of building, begin to bloom at a very early age, and are very reliable bloomers. Greater planting of the larger rhododendrons will undoubtedly follow in those areas where the dwarfs prove reasonably satisfactory. With what is now known about the culture of rhododendrons, it would seem that they can be grown in a wide range of climatic situations provided they are given a treatment specifically indicated by the soil and climate of the area. Under the most unsatisfactory conditions, they can often be grown in raised beds of sawdust or peat, or a mixture of the two. Of course, the feeding has to be geared to the particular medium in which they are growing, but that can be done.
Among plants to associate with rhododendrons and azaleas, some of the types of heather or heath are very useful. Requiring about the same growing conditions as rhododendrons, the heathers, using this term to include both the Callunas and the Ericas , make good ground covers. Of course the taller growing heaths if used at all must be in the background, or among the taller rhododendrons. As ground covers around the low growing rhododendrons or azaleas, only the very low growing heathers should be used. They will rather effectively keep down weed growth, once they are established, and provide out of season bloom if the varieties are well chosen.
The purchaser of rhododendrons today does not have so much trouble with the growth of shoots from the under-stock as was once the case. Most rhododendrons now grown by the larger producers are from cuttings. With these plants the roots are of the same variety as the tops, and any suckers can be retained to increase the density of the bush without danger of their being different in flower character. With some of the older grafted bushes, however, we will have to be on the lookout for under-stock shoots as long as the plant is a factor in the landscape.
The new Rhododendron Book, the successor to "Rhododendrons 1956," is scheduled to appear in 1961, five years after the previous book The contents are fairly well determined now, and various people are working on the chapters. It is hoped to revise the ratings as to quality and hardiness, and to include ratings of a great many additional varieties. There will also be many new features quite distinct from those found in the previous book. It appears that the supply of "Rhododendrons 1956" will be exhausted before the new book appears.
We should know more about the nutrition of rhododendrons, or for that matter about plant nutrition in general. The nutrition of any plant involves two things, the specific requirements of the plant, and the specific characteristics of the soil in which it is to be grown. If a gardener knows his own soil and its peculiar requirements as to fertilizer elements, he should be able to grow rhododendrons without too much trouble. Essentially the same nutrients may be supplied as would be required for most other plants. The main differences would be the necessity of keeping the pH at a rather low level, perhaps no higher than pH 5.5 to 6.0, and the nitrogen should be applied in the form of ammonium rather than nitrate material. Aside from these two things, the feeding of rhododendrons and azaleas is not very much different from that required by other plants.
More and more rhododendron growers are thinking of foliage as well as flower characters. The general bush type and character of the leaves are factors in the landscape twelve months of the year, whereas the flowers are important for only a few weeks. Quite a few rhododendrons would make attractive, broad-leafed evergreen shrubs even if they never bloomed. However, with the attractive foliage, plus the wonderful blooms that a good rhododendron variety can produce, we have about the ultimate in landscape value.
The hardiness of a rhododendron clonal variety does not change except as it is affected by the growth status of the plant. If the plant is succulent and growing rapidly, it is more susceptible to injury by cold than if it is in a hardened, mature condition. With the species rhododendrons, grown from seed, however, we may expect a certain amount of variation to appear among the seedlings. The fact that a species has a hardiness rating of H-4 does not mean that we may not find occasional seedlings which are considerably hardier. It is unfortunate, perhaps, that hardiness comments about species are often made after observing one or two plants over a period of time in an Arboretum or Botanic Garden. It is obviously impossible to grow several hundred seedlings of a single species in a Botanic Garden in order to find the hardiness range. The determined rhododendron fan who wants to grow a species a little too tender for his climate should not be deterred from raising a number of seedlings and attempting to find a plant or two which would display hardiness greater than that of the type. Just as some species breed very nearly true to type from seed so far as visual characters are concerned, some may show very little variation in hardiness. On the other hand, some species are extremely variable as to visible characters, and they may also be variable as to resistance to cold.
Names of varieties to which awards were made during the 1959 Show season, and a list of newly registered American varieties will be published in the January Bulletin. Some of the names have been approved by the International Registrar, but others are still being considered. In some cases, other names have had to be submitted as the ones first suggested were deemed not in agreement with the Code of Nomenclature. These things sometimes take a little time to work out.
- J. Harold Clarke