Rhododendrons In The Sierras
Francis W. Mosher Jr., Woodacre, California
In the shadows of giant Ponderosa and Jeffrey pines on the western rim of California's Sierra Nevada mountains, Leslie and Vida Alexander have successfully developed an experimental rhododendron garden one mile south of the El Dorado National Forest boundary.
After six years of effort, Mr. and Mrs. Alexander now have, at an elevation of approximately 2,500 feet, a collection of more than 180 rhododendron species and hybrids surrounding their home. All are fenced against the depredations of hungry deer.
More than thirty miles separate the Alexanders from the nearest member of the California chapter, American Rhododendron Society. Despite this isolation, they have gone right ahead on their successful project.
This energetic and ambitious couple, upon retirement, built their own residence on a knoll near the pioneer gold mining "ghost town" of Nelsonville and the early days lumbering center of Mosquito Valley, nine miles north of Hangtown, now known as the thriving city of Placerville, California. Lumber for their house came from trees cut down on the homesite.
Securing plants from Pacific Northwest and California propagators, Mr. and Mrs. Alexander set out to prove that El Dorado county's hot summers and freezing winters could not stop them. Ten hybrid varieties and a dozen species failed to survive. But today the Alexanders have more than 180 kinds thriving under English walnut, redwood, black ash, maple and native pine trees.
Heaviest snowfall measured in their garden at any one time amounted to two feet with very little damage resulting. Highest daytime temperatures have reached 100 degrees Fahrenheit while the lowest night time mark recorded was 6 degrees below zero.
In order to increase the number of their most thriving and colorful varieties, Mr. Alexander operates a small plastic covered propagating house equipped with automatic mist sprinkling system and thermostatically controlled bottom heating units. In addition, he is experimenting with a controlled auxiliary lighting system, automatically operated which provides artificial light and speeds-up plant growth.
With no experts in their district to advise them, the Alexanders have developed their own garden system through trial and error. Their successful method includes the annual collection of a dozen or more truck loads of forest litter that consists of pine and oak leaves and stems, poison oak, dried range grasses, etc.
This material is dumped into a giant storage bin and left outside to "breakdown" over the winter months. Each spring eight to ten inches of this bounty from nature's forests is spread over the rhododendron beds.
Before planting their first rhododendrons on top of a decomposed granite base, Mr. and Mrs. Alexander first laid down a heavy layer of pine sawdust taken from abandoned saw mill sites in the neighborhood. A blanket of this well rotted sawdust, at least a foot thick, forms the base all over the experimental garden.
Early tests with various types of commercial fertilizers convinced the Alexanders that nature's way is best for them. Unless a rhododendron plant is in distress, no commercial fertilizer is used. Recently the couple have experimented by applying a dry 0-10-10 fertilizer after flower buds have formed but no conclusive results have yet been obtained.
Very little fall watering is required. In really hot summer months, the Alexanders run garden sprinklers as often as three times per week. Based on their experience to date, Mr. and Mrs. Alexander name their Top Ten hybrid varieties as:
- 'Anna Rose Whitney'
- 'Mrs. Tom Agnew'
- 'Purple Splendour'
- 'Mrs. Charles Pearson'
Their favorite rhododendron species* include the following ten:
- R. aberconwayi
- R. burmanicum
- R. calophytum
- R. ciliatum
- R. dalhousiae
- R. griersonianum
- R. macrophyllum
- R. spiciferum
- R. odoriferum
- R. johnstoneanum
Mr. and Mrs. Alexander are constantly on the look-out for new hybrids and species adaptable to their area and promise to continue their experimental garden project. Their efforts are being closely watched by El Dorado county gardeners and more and more rhododendrons are being planted in Placerville and vicinity each year.
*Note: Some of these species could hardly be expected to withstand -6°F so we assume these are personal preferences and not necessarily being grown successfully in the garden described. - Ed.