Species In the Garden
By Cecil C. Smith
Here in the Willamette Valley of Western Oregon a higher percentage of selected species might add to the interest and year round beauty of many gardens, particularly the more sheltered ones. More species flower in April than any other month, while the hybrids flower more in May.
Hybrids generally flower more profusely and have larger blooms than do species, although many of the latter flower regularly, and many have enormous blooms. In a cut truss show, the crosses will draw most of the attention of the visitors. Many trusses which have been cut and separated from the plant may not appear particularly impressive, while the whole plant in flower might take the honors. This is the case, I believe, much more frequently in the species than in the hybrids.
When it comes to foliage, I submit that in a group of a hundred selected species, the least interesting will compare favorably with the hybrids having the most interesting foliage. It would seem that in hybridizing, too little attention has been paid to foliage and plant character. Take R. campylocarpum with its interesting twisted leaves, bright green on top and a flashing glaucous under surface and attached to a plant of great character. In all its fine flowered hybrids, where can you find one that can compare with the parent?
In a garden which does not have frosts after the first of April to damage the bloom and new growth, there is a wide selection of species of varying sizes which can be grown well. For other locations there are many later growing kinds which might make up the majority of the specie plantings. It is worth the while to take the chance of frost damage to a few plants but not to a sizeable proportion of the garden. There-growth is not apt to set buds, and some of the first growth which remains might have damaged foliage.
Rhododendrons with a thick indumentum on the under surface of the leaves are plants of interest, and the presence of the indumentum is an indication that the new growths maybe very beautiful as the leaves unfurl, changing from day today for weeks.
In the Haematodes sub series of Neriiflorum are found some species with finely felted leaves and year old stems. R. haematodes itself, R. mallotum and R. beanianum are some of them. R. mallotum is a slow growing, dome shaped, densely branched plant with heavy, rich brown indumentum showing up well, because the leaves, large for subseries, hang almost straight down. The stems also have the same covering, which lasts for several years. By the time the plant is several feet high, the effect is startling, and it is to be seen twelve months of the year. Beanianum has a chocolate brown indumentum and stem covering, and it too, is very effective as a foliage plant.
Another group of dense, dome-shaped, but somewhat dwarfer plants of interest are found in the subseries Caucasicum, of series, Ponticum. Among them are R. degronianum, R. makinoi, R. metternichii, R. smirnowii, R. ungernii, and R. yakushimanum. The interest of the new and the old foliage will more than makeup for the lack of first rate blooms in most of them. The unusually long, wooly tomentum underneath the leaves of R. smirnowii retains its whiteness for along time as does the thinner coating on the stems and buds.
R. makinoi, with dark leaves very narrow for their length and all radiating from the tip of the branch, is effective. The species is either quite variable or there is considerable mix-up in species under that name.
R. yakushimanum, from the Isle of Yakusima, has silvery white new growths changing to orange underneath, and the white film remains on the upper surface until the winter rains wear it off. The upper surface then is medium green, smooth and shiny. To observe this plant through all its growth phases would endear it to any gardener. But there is more - it is even said to have a good bloom which, I admit, is more than can be said of many other species with a beautiful chassis. Yes, R. yakushimanum has everything.
The large Taliense series has many plants of fine character from dwarf to medium size. In the Adenogynum subseries, R. bureavii stands out because of its very dark foliage with a reddish cast to the upper surface and a very thick rusty red tomentum underneath. The new shoots are startling in their constantly changing color as they mature. R. bureavii may not bloom from seed for twenty or twenty five years, but if it is like some of its close associates, that is just as well.
Another plant of quality is R. bullatum in the Edgeworthii series. It is unfortunately quite tender. The crinkled leaf's upper surface is interestingly different and in the Exbury A.M. form, the shoots and leaf under surface are covered with long brown bristles. The white A.M. form has bloomed here outside in a most sheltered place. These two would make fine greenhouse shrubs.
There are many larger growing shrubs or trees having interesting and distinctive foliage, which do, and look best in cool sheltered, moist woodland surrounding. R. calophytum has relatively narrow leaves a foot long or much longer, concentrated thickly at the ends of the branches. They grow upright until maturity, at which time they reach up and out to form a huge funnel which is not quite as effective as the first phase.
In the Falconeri series, R. eximium stands out as a foliage plant because of its fairly large leaves with a thick reddish-brown wool underneath and very prominent venations between which pockets are formed. The newly formed leaves have powdery, reddish tomentum on the upper surface which persists for months. The stems are sturdy and covered with a light gray coating.
R. falconeri itself, is a larger edition of R. eximium in all its parts. It is one of the great, if it is grown in the most sheltered woodland and given, lots of water in dry spells.
In the Grande series, R. macabeanum is rated highly with its large leaves, dark above, and almost white beneath. R. sinogrande has the largest leaves of all the rhododendrons. They grow up to thirty inches long, and have a thin gray covering underneath.
As striking foliage plants, yakushimanum, mallotum, and bureavii might be called the little three, and falconeri, macabeanum, and sinogrande, the big three.