The Pacific Northwest is natural rhododendron country. In that narrow belt along the Pacific slope running from Vancouver and Victoria to San Francisco, the winters are tempered by warm waters. The air is moist year-round, there is very little extreme summer heat, and the soil is naturally acid.
All this adds up to a perfect rhododendron formula. Also, the soil texture is mainly light in this section, running from peat to good sandy loam; heavy clay loam is found only occasionally.
Gardeners who live within hailing distance of the waters of Puget Sound, which includes many islands, can grow the full range of British hybrids, as well as the majority of rhododendron species from all parts of the world.
Those who reside at a distance from the immediate influence of the warm currents naturally have to be a little more careful about their selections. But there is a wealth of fine varieties they can grow.
Coastal Species
Three species of rhododendrons are native to the Pacific Northwest. Rhododendron macrophyllum (AKA californicum) is an evergreen that puts on a good display in the wild but is an indifferent garden plant and of little value for hybridizing.
Rhododendron alriflorum is an interesting deciduous sort that grows in the high Cascades and other mountain ranges of the area. Both species are scattered over a wide area up and down the coast.
Rhododendron occidentale, a very fine species of the azalea series, grows in Oregon and California. This species has been used to improve deciduous azaleas to a great degree. In addition, a natural hybrid between R. californicum and R. occidentale has proved to be a fine “azaleadendron.”
English Hybrids
England, of course, is the source of many of the fine hybrids. The British have many more years of experience in hybridizing. They also have flowering size plants of all known species from which they can select parents.
However, a great deal of intelligent effort is being expended in the Pacific Northwest to overcome this English advantage. More and more fine species appear in Northwest gardens every year, and these are important to a hybridizing program.
There’s much importing from England, both of species and hybrids, and many fine British forms are now big enough that nurserymen are propagating for commercial distribution.
Across the Sound on Bainbridge Island, Herbert Ihrig was a pioneer in collecting top-grade rhododendrons.
His interest was in such important and diversified species as Rhododendron thomsoni, which takes years to produce its intense red bells; Rhododendron yunnanense with its sprawling, vine-like branches and soft mauve flowers; and Rhododendron moupinense, a compact mound with large white flowers appearing in early winter.
Both hybrids and species are featured in the garden of Donald Graham, Seattle.
A massive specimen of Rhododendron campylocarpuni from his garden won the sweepstakes at the Seattle Flower Festival Show in 1951. This plant had thousands of lovely yellow bells which almost covered it.
Seattle’s Great Rhododendron Collections
There is a wealth of hardy rhododendrons at the University of Washington Arboretum at Seattle. Director Brian O. Mulligan strove to have representatives of every series in the genus. A huge example of Rhododendron sutchuenense, which is sheltered from March frosts, causes visitors to marvel at its bountiful supply of orchid pink flowers in early spring.
In May, drifts of Rhododendron augustini, ranging from sky blue to deep purplish-blue, are startling. At this time of year, the area known as the Rhododendron Glenn is gay with hundreds of varieties in full flower.
Also based in Seattle, Halfdan Lem has assembled a wonderful collection of rhododendrons. He is one of the few men in the Northwest who has, to his credit, the origination of new top-quality hybrids. His ‘Lem’s Goal’ has attractive 4″ inch flowers of a good shade of creamy yellow.
The parents are ‘Lady Bessborough’ and ‘Azor’. Mr. Lem’s Rhododendron tacoma variety ‘Mrs. Geourge Franklin’ is another first-class American hybrid. It has attractively formed 5” inch flowers, which are a unique chartreuse color. The parentage is Loderi Rhododendron ‘King George’ and ‘Lady Bessborough’.
Some Choice Seedlings From England
Many seedlings from crosses made in England have been grown to flowering size at the Lem place. Among the better ones are ‘Flame’ (Rhododendron coronis crossed with Rhododendron griersonianum), boasting huge pink trusses, and ‘Anna’ (‘Norman Gill’ crossed with ‘Hon.
Jean Marie de Montague’) with its wonderful carmine-pink flowers. There’s also an unnamed seedling from the cross Rhododendron lacteum and ‘Mary Swathling’, with bronze yellow buds and open flowers of real butter yellow.
Another fine seedling from an English cross has been raised by Andre Ostbo at his nursery, King of Shrubs. The cross was also named ‘King Of Shrubs’ and was the first hybrid to receive the Preliminary Award from the American Rhododendron Society. It has large trusses consisting of 9” to 10″ inch flowers of porcelain rose.
The late James E. Barto of Junction City, Oregon, was one of America’s greatest authorities on rhododendrons, with an extensive collection that included hundreds of species. He also made many crosses, some of which preceded the same crosses to be made in England.
Mr. Barto’s crosses still hold their own with the best of the new ones. Mrs. Horace Fogg of Tacoma named one of these ‘Renaissance Red’. It’s crossed from ‘Peter Koster’ and ‘King George’. Its color is unique among rhododendrons.
Hybrid Pioneer H.L. Larson
H. L. Larson pioneered in growing rhododendrons in Tacoma, Washington. Years ago, he collected species seeds from a number of sources, including the old British Rhododendron Society, a collector in Darjeeling, India, and the Lu Shan Arboretum, Kiukiang, China. Many excellent varieties of species that are now of flowering size resulted from this project.
Mr. Larson had not neglected fine hybrids and quickly assembled a rather complete collection of top-grade forms. He also grew two fine American hybrids. One grew from seed received from China and was determined to be a natural hybrid of Rhododendron souliei.
It has large saucer-shaped flowers of straw yellow, while the buds are Mandarin red. This hybrid ranks with the very best produced anywhere. Mr. Larson has named it ‘Virginia Scorn’. The other hybrid is ‘Mrs. Horace Fogg’, a cross of Rhododendron griersonianum and Loderi Rhododendron ‘Venus’.
The flowers are large, 5 1/2″ inches across, and colored Neyron rose. The throat is crimson, and the tip ends of the lobes a deeper shade of Neyron rose.
Other Rhododendron Pioneers
Two very unusual deciduous azalea hybrids are credited to I. S. Broxson of Tacoma. One is a Rhododendron occidentale cross which has flowers 31/2″ inches across. The corolla is white, with pale pink stripes running down the center of each lobe.
It also has a pale yellow blotch. The second hybrid is a Rhododendron molle cross. It is of the Ghent type with 2″ inch flowers and extended stamens. The color is signal light red – an unusually good shade of red for this type of azalea.
The collection of Mrs. Tressa Coen embraces a number of fine species, including a large plant of Rhododendron augustini, a deep blue form which won the Affiliated Societies Medal, Royal Horticultural Society, London, at the 1951 Tacoma Rhododendron Show.
Large specimens of Loderi Rhododendrons ‘King George’, ‘Betty Wormald’, and ‘Mrs. G.W. Leak’ put on a grand annual show at Mrs. Coen’s garden.
Azaleas also hold a prominent place in this garden. One particular planting of evergreens is a fine demonstration of what can be done with a mass grouping of azaleas.
It includes Rhododendron macronatum and orchid ‘Atlanta’, blending their colors with many others to form a veritable Persian carpet. Orange, red, and yellow deciduous azaleas also produce a riot of color at the Coen place every spring.
Finally, a very fine example of the exotic ‘Lady Chamberlain’, Exbury variety, is Mrs. Coen’s pride and joy. The pink trumpets that cover this one charm all beholders.