QBARS - v12n1 About The Habit and Shape of Rhododendrons

About the Habit and Shape of Rhododendrons
By Cecil C. Smith, Aurora, Oregon

In setting up a score card for rating plants, the American Rhododendron Society has given flower character 50% and plant character 50% Under plant character foliage rates 30% and habit 20%.
From the literature and from what plant enthusiasts say, I gather that the character of the flower actually has about twice as much weight in rating as does the plant habit. With people who just like flowers the plant is thought of in many cases as something necessary to hold the blooms up.
I suggest several ways of increasing the interest in a rhododendron planting when out of flower. It helps to have 10 or 20% of the planting composed of lepidotes, which have on the average much smaller leaves than the elepidotes. Many of the former change color in winter from various shades of green to brown and purple shades, which adds much to the interest of the winter scene.
Another way to increase flower interest is to have species as well as crosses if conditions are suitable. Hybrids as a rule have larger flowers, more of them, bloom at an earlier age, and are easier to grow. On the other hand, species generally have beautiful foliage and have greater variation in both shape and color. They also are apt to vary more in plant shape, especially if they are seedlings.
A third method of having off season interest is to allow plants, as they grow, to vary in habit. Most writers on both the East and West coasts and in England and Scotland consider that the ultimate in rhododendrons are those that make a compact round or dome shaped shrub and, I might add, are so full of bloom that you cannot see any foliage.
This compactness is usually brought about by nurserymen pinching out the new single growth bud on the young plants after which several dormant growth buds start. For some years these bushy plants probably look better than un-pruned leggy ones. Customers almost always want this type and so the propagators try to furnish them. After some years the branches on many of these plants begin to settle, an open space develops in the middle, and they become much less attractive. (Fig. 2) If these plants are not clothed with leaves nearly to the ground their exposed intricate branching pattern will look brushy and floppy. This is true of many R. griersonianum hybrids which would best be grown with only 2-3 trunks.

Multiple stem griersonianum hybrid Double-stem griersonianum hybrid
Fig.2  A multiple stem griersonianum hybrid
with many weak branches.  Several
years ago when purchased this was a
compact, busy plant.
Fig. 3  A fine specimen of griersonianum
hybrid illustrating a more upright
habit, but having only a double stem
at the ground.

The rhododendrons in our planting which I think have the best habit, have one more or less dominant trunk. They have a simple sturdy branching habit which is usually partially exposed, and which adds to, rather than detracts from their appearance. Plants that were bushy and compact when purchased have so many thin weak branches now that they cannot be held erect, and now are open at the top.
A variety which holds its leaves but one year and is intricately branched can look like a jungle, if limbs show through, while a simple sturdily branched one could be the more interesting for scarcity of leaves below, because it would make for variety in the planting. (Fig. 3)
By the time the bole of a plant is four inches or more in diameter and runs up a foot or two with sturdy branches not too dense a much finer plant is in evidence. We should have more of them.
A round bushy plant is apt to get wider and wider in relation to its height as it matures, and I think a good share of the planting should be of that type. But some plants that are taller than they are wide will make for variety, and one with a single dominant trunk is apt to be tall.
One can sometimes find a small plant in a nursery with a single leader whose terminal buds were missed by the nursery man, and with a little attention through the years can be kept that way.

Single stem plant of the same variety
Fig. 4  A single stem plant of the same variety.  Note the pleasing
appearance after the passing of a number of years.

Some eight or ten years ago I trained several small typically branched hybrids to form a main trunk, and now one of them is about seven or eight feet tall. (Fig. 4) After observing the results for a few years, I began training more, and now I wish I had started earlier. Hybrids which show evidence of the arboreum , fortunei , grande , and falconeri series can often be made to form a leader, as these naturally grow to be trees. On the other hand, most of the thomsonii , neriiflorum , taliense , and their hybrids have the tendency to grow rounded, and it is best to permit them to form that type of shrub.

R. 'Loderi King George'
Fig. 5  'Loderi King George' in Cecil Smith's

Even in a planting of the dwarfs, as the lapponicum series, it will be noted that there is quite a variation in the growing habit. A few, as flavidum and rupicola , are quite upright in growth. If these dwarfs are in full or nearly full sun, they do not need clipping for many years, and they will take on a characteristic more or less irregular shape that would be hard to match by hand pruning, if that should be necessary.
So the next time you go to the nursery after a rhododendron, get a whip with a branch or two along the side. Remember in five or ten years it can be the most interesting plant in the garden.