Two Decades Of Rhododendrons
Eldred E. Green, Chicago, Illinois
Two events are responsible for my continuing interest in rhododendrons and azaleas for the past twenty years. The first event happened on a Saturday afternoon in 1937. As the most southerly-living member of the Garfield Park Conservatory horticultural staff. I was assigned the task of paying a courtesy visit to the flower show of the Hammond Public Schools. This show was directed by a horticulturist on the staff of the school system and was very creditable. It was unique in that the school system was encouraging gardening through a staff member trained and assigned to the specific job.
After the usual amenities, I was on the verge of leaving when the school horticulturist suggested that I might be interested in a garden nearby. We went to a garden in one of the choicer residential areas of Hammond. The area was on a small sand ridge with a growth of scrubby oak. The house was on a wide lot and the ample side yard was filled with choice plants including numerous rhododendrons, large specimens of azalea, heather, magnolia, etc. All were in excellent health and many were quite large. I was told that this was the residence of Dr. L. L. Caldwell, superintendent of the Hammond, Ind. School System.
With my idea that these Ericaceous plants could not be grown in the Chicago region thoroughly exploded, the next step was to find out why the erroneous idea was so prevalent even among professionals. As I started to dig into the literature I was loaned a copy of Rhododendrons and Azaleas by William Watson. This thin little book did a fine job of convincing me that the cultural aspects were easy, in fact rather simple. Use your native soil, add humus, build up the beds instead of sinking them, give shade. This was the sort of thing that was routinely done with roses, peonies, iris, etc. Pick the right situation and then modify the soil as needed.
The next step was to find out where these plants were being grown. L. H. Bailey's Cyclopedia of Horticulture gave variety lists for Boston (Arnold Arboretum), Rochester, N.Y., and several other places. Native species were listed in catalogs from the Asheville, N.C. region. Next a call was made on the Weather Bureau. Data for Boston. Rochester, Asheville. anal Cleveland was obtained. The data showed that all of these places had temperatures that went as low as Chicago. Therefore the varieties that were being successfully grown at these places would he hardy, as far as temperature is concerned, at Chicago. The next problem was to find a suitable site.
From studying the available literature, including some state bulletins, the desirability of a sheltered situation was brought out. Especially during the hottest part of the summer and during the winter. Finally a decision was reached to take a problem area on the north side of a porch and try some plants there. There was a slight upslope from the rest of the yard to the porch so that drainage would be away from the planting. The natural soil was a stiff clay so it was decided to remove it. A fine sand with rotted oak leaves and peat was put in and collected plants of the native species were ordered and planted during the Spring of 1939.
The following Spring. as all the plants were still alive and growing saw the addition of some hybrids and other cultivated species. This included R. 'Catawbiense Album', R. 'Mrs. C. S. Sargent', R. 'Roseum Elegans' and R. poukhanense. R. 'Yodogawa', R. mollis and R. japonicum in the azalea line.
This original planting persisted for many years, in fact a few of the plants are still going along. Many of the original plants were lost due to the mistake of planting flowering dogwood as a background. The flowering dogwood created so much shade, in spite of trimming, that the original plants in the back were killed out eventually. Ones in the foreground have lived on and increased in size.
In 1912 it was decided to try some rhododendrons on the north side of a summer cabin located in the woods some 20 miles away. The soil was a stiff clay and the drainage was toward the cabin. Watering in the summer would be a problem. Oak leaves would be abundant as the entire area was heavily covered with oak trees. Again the native species and collected plants were procured for a trial. No sand or good soil was handy - just stiff clay and piles of year-old oak leaves.
Digging out the stiff clay would only create a cistern so the planting was made by merely scrapping off a couple of inches of the sod and then placing some wet oak leaves on the bottom. The balls were set on this and then mounds of wet oak leaves were packed around them.
This simple method has been followed ever since except for very small plants. For these a mixture of peat, loam, sand is used with a mulch of oak leaves. At no time has an attempt ever been made to bury the balls. The balls are placed in a shallow depression, three or four inches deep and lined with oak leaves, and then whatever soil mixed with peat, is drawn up around them and the whole area covered with wet oak leaves. (These are not rotted leaves but merely wet. They are raked in the fall and piled. During the winter they become wet and pack down. It is in this wet condition that they are used.) A mulch of several inches of these wet leaves is maintained. During the summer an occasional watering is given if the plants show signs of wilting. The first summer this watering is confined to the ball. In later years the area around the plant is watered.
During the early years the war made fertilizer materials scarce and no fertilizer was used on the plantings. Since then a special fertilizer has been used. This has been Reliance Azalea food, or Sears Evergreen fertilizer. The results from using these have been excellent. One feeding in early spring is the rule with some sprinkled in among the wet oak leaves when plants are set out.
Fig. 32. R. 'Conemaugh'
C. Smith photo
During the early years the rhododendrons tried were either of the ironclad Catawba hybrids or native species. Azaleas were in the Ghent, mollis, or tough species groups. For many years the plantings were confined to the constant shade provided by the north aspects of buildings. In time space became a problem. So several years ago a planting was tried in among the oak trees. This has proved satisfactory. Areas were selected where the shade was so dense that grass did not thrive and the soil was built up. In this case an edging of aluminum has been used to hold the material of the bed and some peat and lots of oak leaves have been used to raise the level. There has been some more browning of the leaves during the winter than on the plants against the buildings, but this has not been serious except on those plants that were closest to the edge of the trees where the winter sun could get on them. Apparently there is a great deal of variability in sun tolerance as some kinds are quite resistant (R. smirnowii) while others are sensitive (R. discolor, R. 'Purple Splendor').
Lately a number of Gable hybrids have been planted and a number of species (Fig. 32) came through. Last winter these plantings came through -20° F. There has been some bud damage on a few, others suffered some leaf damage but on the whole they have been satisfactory. As these plants were only planted for two or three years they have not become thoroughly established and any difficulties may not he typical. Azaleas are in the same condition. Many hardier Gable originations are being tried. With the deepest snow in a decade, it is difficult to assess the results. Rabbit injury was most severe. Many azaleas were pruned back to the snow line so no accurate deductions can be made.
Two decades of growing rhododendrons in the inhospitable Chicago area climate have proved two things. One that they can be grown. And secondly that there are many, many kinds that will prove satisfactory under the proper conditions. As I have lectured about growing these plants instances of others growing them have been brought to my attention like the magnificent azaleas in a garden in the extreme northwest side of the city. These are mollis and Ghent hybrids and are currently about 4 feet high and as wide. Truly magnificent when in bloom. Some terrific plants of rhododendrons in West Chicago, and individual plants here and there all confirm the idea that there is no basic reason why the Chicago area should not grow these beautiful plants. The important factors here seem to be (1) shade, especially for the evergreen sorts in winter, (2) humus-rich soil, and (3) proper selection of kinds. It is in the last factor that the new Midwest Chapter should prove most helpful. The exchange of information will broaden the knowledge of kinds that are being grown and will lead to more of them being tested. This will make the Chicago area more rhododendron conscious and will greatly expand the area of rhododendron culture.