QBARS - v12n4 Rhododendron Notes

Rhododendron Notes

Hot, dry weather seems to have caused more than usual leaf burning on certain rhododendron varieties in the Portland area. Removal of scorched leaves will not only improve the appearance of the plants but will lessen the chance of Botrytis infection of the dead tissue which, once started, may extend into living tissues.

We see more and more rhododendrons being handled in cans, and many other kinds of plants are now grown almost exclusively in containers. How the trend will develop from now on we do not know, but there are certain advantages to growing Rhododendrons in the soil and moving them balled and burlapped.

The frontiers of rhododendron growing are being pushed further each year as new methods of handling soils and water, and offsetting alkalinity, and unfavorable temperatures are developed. Hardier varieties, with desirable flowers, will become available. We may never be able to say that rhododendrons can be grown anywhere in the United States but their range will be far greater than has previously been thought possible.

There is a great variation in the types of horticultural peat moss available. Possibly one might be as good as another for incorporating into the soil. However, for use in propagation, and especially for growing rhododendron seedlings, some types are much better than others. We have tried some recently which was finely ground which was extremely difficult to wet, and which had to be fertilized much more than another type in order to get satisfactory growth of seedlings.

Recent experiments with forage crops have indicated that plants having adequate nitrogen will suffer from drouth much less than plants having an inadequate supply. Whether this principle will apply to all plants has not been determined but it is something that might be given consideration by the gardener with a flair for experimenting.

It seems as if centennial celebrations are the style for all sorts of things and places. We don't know just when the centenary of the modern rhododendron would occur but there are several varieties which are past the 100 year mark. At any rate it was about 100 years ago that the foundations for modern Rhododendron growing were being laid by the early plant breeders, and before the work of Mendel was available.

- J. Harold Clarke

Here in the northwest our long dry summer damaged native plant material such as dogwoods, mountain ash, maples and native shrubs- as well as rhododendrons, azaleas and other plants in our gardens. This summer many of our nights were hot and dry instead of the cool moist ones we usually experience. Collections of rare primroses and other perennials suffered badly.

Moles worked deep this summer often leaving no trace on top of the ground. Much plant injury blamed to other causes was found to be caused by moles working around plant roots. One of the best ways to keep moles out of the garden is dusting with chlordane. The fall is a good time to apply it with a dust gun so that winter rains may wash it in.

Plants with tight compact growth such as 'Souvenir of W. C. Slocock,' 'Devonshire Cream,' 'Moonstone' and others are difficult to water with overhead watering. They literally shed water and their roots will often be found to be dry when other more open growing plants have ample moisture. These plants should be checked during hot weather to make certain they are receiving sufficient moisture to remain in good shape and set buds.

Few plants give more spectacular fall coloring than Knaphill azaleas. Leaves of some will turn a beautiful dark red, others will color orange, shades of yellow, some show blends of color. And in the spring nothing is more beautiful than a mass planting of Knaphills. Beautiful big flowered whites, pinks in many shades, light to dark yellows, oranges and many wonderful blends. Often flowers are ruffled and very large. During the past three years many beautiful seedling Knaphills have bloomed and a number of fine plants well worthy of naming have been selected. These are now being successfully propagated from cuttings. Often these cutting grown plants will bud when only two years old.

R. williamsianum hybrids, 'Bow Bells', 'Moonstone' and others are being quite successfully grown in many parts of the country. In the Northwest they are rapidly increasing in popularity for foundation plantings for low "ranch-style" homes. Few hybrid rhododendrons can compare with 'Bow Bells' and 'Moonstone' for all around fine growth habits, good flowers, and heavy budding and hardiness.

Among the good plants to grow with rhododendrons are gaultheria. There are many, most are low growing ground covers, a few are shrubs 2 and 3 feet high. They bloom, usually in June with white or pink flowers, then bear fruit; red, black, white or blue berries. Some have nicely colored fall foliage. Three fine ground covers which can be grown even on top of roots of large rhododendrons are Gaultherias nummularioides growing about 4 inches high, compact and dense with hairy stems and leaves. Flowers are white followed by large black berries. Does well in the west in either sun or shade. Gaultheria miqueliana said to grow up to 8 inches high is usually only -1 inches. It likes light shade. White flowers followed by large white berries. Leaves are beautifully veined and often color in the fall. A third is G. procumbens the true wintergreen. It grows only 2" or 3" high, likes sun or shade, has large red berries and colorful fall foliage.

- Bob Bovee