Tropical Rhododendrons for You

Vireya 'Aleksandre Isayevich'

Vireya ‘Aleksandre Isayevich’

It is a most lamentable form of floral deprivation that rhododendrons – those magnificent relatives of the azalea – are seldom seen in Los Angeles. The word rhododendron is derived from two Greek words: “rhodon,” meaning rose, and “dendron,” meaning tree. In fact, the rhododendron is a large woody shrub with thick, leathery dark green leaves and dense clusters of blooms; individual flower clusters may resemble, from a distance, oversize roses. Azaleas, ubiquitous local constituents of the rhododendron clan, can be seen in almost every shady spot in this city. Yet the rhododendron itself, which is a larger version of the azalea – with showier flowers and bigger leaves than the azalea and a mature height of 5 to 6 feet or more – rarely is encountered.
The dearth of rhododendrons in Los Angeles is explained by the quality of our soil and water. Whatever the azalea needs to prosper, the closely related rhododendron requires in a more critical way. And let’s be honest. Most of the azaleas in this city – and there must be a few hundred thousand of them struggling to exist at any given moment – look rather pathetic within the first few years of their garden lives. As often as not, leaves of azaleas are yellow with green veins (a sign of alkaline soil) or the margins of azalea leaves turn brown (a sign of salty water). The alkalinity of our soil and the salinity of our water do not affect the leaves of most ornamental plants in this way. The point is merely that azaleas are more sensitive to alkaline soil and salty water than the average plant.
If azaleas decline in health due to soil and water that are not to their liking, rhododendrons will exhibit a similar, if not more rapid deterioration when planted in our gardens. Rhododendrons grow wild in a variety of Asian habitats – from tropical New Guinea and Malaysia to elevations of more than 15,000 feet in the Himalayas. Regardless of habitat, they are accustomed to living in air that is saturated with mist, their roots growing down into perfectly drained soil.
To learn how to create the proper conditions for the culture of rhododendrons, a trip to the Mildred Mathias Botanical Garden, on the UCLA campus in Westwood, is advised. This garden is one of the true treasures of our city, although it is hardly known to the general public. Many species seen nowhere else in California, and perhaps nowhere else in the United States, have been planted here. Located on the corner of Hilgard and Le Conte avenues, the garden is open free to the public, seven days a week, with group tours available. For more information, call (310) 825-1260.
In the UCLA garden, a group of Vireya rhododendrons, from Malaysia, are congregated in a special planter whose soil consists of peat moss and perlite. Overhead, the high branches of mature trees serve to protect the rhododendrons from the ravages of sun and wind. In our dry climate, the rhododendron should be grown in high shade, under the cover of tall trees, where the scorch of sun and wind cannot be felt, yet where the ambient light is good and the humidity is somewhat higher than in the open. If your property has no tall trees, your next best bet is to plant rhododendrons against a north-facing wall or fence.
In our area, rhododendrons would be most prudently grown in containers, with worry over alkaline soil eliminated by use of a custom-made soil mix containing perlite, peat most, fast-draining top soil and compost. Watering would be done with distilled water, which, free of salts, would not burn the margins of rhododendron leaves. Fertilization would not be overdone, as rhododendron roots are most efficient at extracting any mineral elements that are available to them.
Lest you think rhododendron growing is beyond the reach of the average gardener, I can assure you that I have seen this plant growing quite well in the yard of a homeowner who did nothing to his plants except water them occasionally. I am convinced that the placement of the plant in question, against the north side of a house in North Hollywood, had everything to do with its success, together with the fact that there are select areas of North Hollywood where the soil drainage is superb.
Be aware that the Vireya rhododendrons at UCLA are frost tender and should not be planted in our colder valleys. Many rhododendron cultivars, however, are quite hardy and will not be bothered by sub-zero temperatures.

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