Congratulations, We Were Successful, We Won!

Adapted and expanded from a talk given at the Northeastern Regional Conference Oct, 2015.


Yes, congratulations we were successful, we, the Rhododendron Society, turned rhododendrons completely around, changed how they were evaluated by gardeners.  Let me explain.

Before World War II   rhododendrons were judged on three characteristics, and there was a priority to the characters.  The first and most important characteristic was hardiness.  I can’t emphasize enough how important hardiness was.  It was exclusionary.  If a plant wasn’t hardy, forget about it. Dave Leach in his book, ‘Rhododendrons of the World’, talked about the importance of hardiness. The ARS assigned hardiness ratings to rhododendrons:  H1, H2 H3 etc.  Remember them?  No one uses them anymore.  Guy Nearing once told me that if one pip in one bud on one of his hybrids blasted over the winter he would discard the plant. Paul Vossburg was a commercial nurseryman.  He grew rhododendrons in an open field with no protection at all. No hoop houses, trees, wind breaks, nothing.  So he had to have very hardy plants that would look great in the spring when the time came to sell them.

But “Mr. Hardiness” was Clem Bowers. Clement Gray Bowers graduated from Cornell University with a Masters Degree in botany in 1925.  In the fall of that year he moved to New York City to become a PhD candidate in botany at Columbia University. I do not know when Clem became interested in rhododendrons but he chose them as the subject of his doctorial dissertation: “The Development of Pollen and Viscin in Rhododendron Catawbiense”.  Now I know that everyone knows what “viscin” is, but just in case you don’t it is the name of the threads that hold rhododendron pollen together in strings.  If you want to see Bowers’ PhD dissertation, just type in “viscin” in Google and away you go.

In addition to his interest in the plant for his research, he also wanted to develop rhododendrons hardy enough to be grown at his home in Mane, New York (just North of Binghamton, NY) where the winter low temperature could go to -40o F.  He spent his first winter in New York reading everything that he could find on rhododendrons and decided in early 1926 that his best chance of developing these super hardy rhododendrons was to cross all the Ironclads, each with each other.

The Ironclads were a group of 14 rhododendron cultivars so identified by Charles Sprague Sargent at the Arnold Arboretum as “Ironclad Hardy at the Arnold” in 1917.  C.S. Sargent was friendly with an English hybridizer, Anthony Waterer, who sent 200 of his named hybrids to the Arnold for hardiness testing in the late 1800s. Waterer had no idea how hardy his hybrids were as they were developed in Southern England and were never exposed to very cold weather.

There had been enormous interest in rhododendrons in this country as a result of the use of rhododendrons imported from England and used as landscape plants at the Centennial Celebration of the American Revolution held in Philadelphia in 1876. The Arnold wanted to obtain some of these English hybrids for trial in Boston.  When Sargent’s friend Anthony Waterer offered the plants Sargent was delighted.  In 1924 Prof Wilson, the new arboretum director, reduced the number to 12.

It was the original group of 14, plus a few other hybrids that were locally known to be very hardy, that Bowers decided to cross, each with each other, about 200 crosses.  In 1926 Bowers was living in an apartment in New York City.  How could he possibly make all these crosses and grow the seed to blooming stage?  Well he found Hicks Nursery on Long Island (a suburb on New York City). Hicks had everything Bowers needed: they had all the Ironclads, plenty of room to grow the seedlings and the knowledge and experience to germinate and grow on the seed.

So Bowers made a deal with Hicks. He would make the crosses and Hicks would germinate and grow the seed.  Hicks would own the plants but Bowers could select and move plants that he thought might be super hardy to his home garden for trial.  Starting in 1926 and for next three years he would travel out to Hicks and make his crosses.  It was during these hybridizing trips that he became very friendly with Paul Vossburg, a young employee at Hicks, and encouraged Paul to make his own crosses.  Indeed Paul copied one of Clem’s crosses:  ‘Mrs. C.S. Sargent’ x ‘Everestinianum’.  There were two Everestinianums at Hicks: the Ironclad form and another that was called “Pink Everestianum”.  They appeared virtually identical but they were slightly different as the ironclad form had a glabrous ovary and the pink form had a pubescent ovary. Bowers used the ironclad form and Paul used the pink form.

Bowers made hundreds of other crosses, many with rh. maximum but none turned out to be useful.  The ironclad crosses were a disaster. The flowers and plants were inferior to the mother plants.   Many were destroyed in the winter of 1931-1932 when the winter dropped to + 5o F with 50 mile an hour winds and no snow cover. Even the ironclads got smacked; ‘Atrosanguinium’ was the only ironclad that bloomed after that winter thus making it the hardiest red rhododendron. (I never see listing in the seed exchange using it or any ironclad for that matter, by people looking for plants hardy in zone 4, 5 or 6.) As luck would have it, Paul’s cross produced 130 seedlings with only three being good and the best of those was named ‘Meadowbrook’, to this day a wonderful rhododendron.  This disastrous experience using the ironclads made a great impression on Vossburg.  From then on he always said, “Don’t use the ironclads”.  (He should have added: “by crossing each with each other). Well I have spent a lot of time on hardiness to emphise how important it was considered and also to give some history that you might not know.

The second most important characteristic was plant habit.  Were the leaves a good color green?  Did the plant hold the leaves for several years to give the plant a full, compact appearance?  Did it just present itself as an attractive plant in the garden 12 months a year?

The third most important characteristic was the flower: its color, size and shape’s

After the end of WWII suddenly everything changed.  Now the most important characteristic was the flower: the color, size and shape.  The second most important characteristic was the flower: the color, size and shape.  And the third most important characteristic was the flower: the color, size and shape.

Rhododendrons suddenly became a flower centric-plant, nothing else mattered. Everywhere you look it is just the flower that is shown, in catalogs, in the ARS Journal newly registered rhododendrons section and in Hirsutum.   How could this possibly happen so quickly?

What happened was the creation of the ARS right after the end of WWII and the New York Chapter a year later.  Right from the very first year the most import chapter event was the flower show. And what was exhibited at the flower show?  Of course the truss and the collar of leaves immediately surrounding it AND NOTHING ELSE.  Suddenly hardiness didn’t matter.  If a plant only bloomed once every four or five years, no problem, show it that year and wow the members.  No one knew or asked how regularly the plant bloomed. Plant habit was not exhibitable as the entire plant itself was never shown, so of course plant habit didn’t matter either.

This forced hybridizers to hybridize for truss only, nothing else mattered.   Frequently new hybrids are exhibited as their initial bloom and there is no knowledge by the hybridizer of the plants’ hardiness or growth characteristics.  That has certainly happened to me.  Initially the plant looks great, but after 9 or 10 years the plant ends up a disaster and is discarded. Of course the answer is to hold off exhibiting the flower until the plant is 9 or 10 years old and the plant habit and hardiness has been seen.  That is mighty hard to do when you are excited when you see the initial bloom on a plant, especially after waiting 5 years to see it.

We are now in the age of polyploid rhododendrons and that fits in perfectly with this truss quest.  Polyploid rhododendrons usually produce larger, more intensely colored flowers, all be it on vigorous plants that some tend to become open growing and too big for the small garden. But of course, since the truss is all that matters, we seem to excuse the open, excessive growth of some of these new polyploids.  I must admit, for the last 3 or 4 years I too have put most of my hybridizing efforts into finding polyploid hybrids with the hope of finding more compact plants, unsuccessfully at this point.

I know that we cannot do away with the truss show, but there are some things that we can do to try to inform everyone about the other characteristics of the plant.  Why not have a little information sheet regarding the entry: In the last 5 years how many times has it bloomed with a full truss? Show a full color picture of the plant from which the truss was cut.  What has been the coldest temperature the plant has been exposed to and still bloomed?

So we have been successful in transforming rhododendrons into flower-centric plants.  The only problem is that the general gardening public is basically interested in great looking garden plants that consistently have nice flowers.  I always remember Joe Cesarini, an old nurseryman friend of mine, who told me in 1964 when I told him that I was going to hybridize rhododendrons, “Dick we don’t need all these new, fancy colored rhododendrons that hybridizers are producing.  All we need is a pink ‘Boule de Neige’ a red ‘Boule de Neige’ and a yellow ‘Boule de Neige’.”

Now maybe we have a solution to this conundrum of beautiful flowers on miserable plants. Grafting.  Using ‘Cummingham’s White’ as under stock seems to change the growth habit of the scion as it matures.  Certainly fruit trees have responded beautifully to the technique, dwarfing the tree but keeping same size fruit. The use of ‘Cunningham’s White’ as understock started in Germany where nursery row after nursery row of different cultivars of rhododendrons all exhibit the same dense, globose plant habit  with, seemingly, no effect on the flowers.

Karl Bernady and George Woodard are two Eastern rhododendron enthusiasts looking into this propagation technique. At the October, 2015 Eastern Region Regional Conference George Woodard brought in hundreds of young plants grafted onto ‘Cunningham’s White’.  Karel gave an interesting talk on his grafting technique.

Plants sold in the big box stores are all container grown using accelerated growing techniques (“plants on steroids”).  Only a few cultivars respond well to this heavily fertilized technique (thus the reason there is such a limited number of cultivars available). Will these grafted plants with CW roots respond as well to these techniques?   If they will, or if another root stock can be found that has the same effect on the growth habit but will also respond to the accelerated growth technique, we will really change the history of cultivated rhododendrons.

Perhaps Joe Cecarini will finally get his wish.