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Journal American Rhododendron Society

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Dr. Glen Jamieson ars.editor@gmail.com


Volume 61, Number 3
Summer 2007

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Let's Talk Hybridizing: Some Like it Hot
Dennis Mac Mullan
Hamburg, Pennsylvania

        Over the years I have written some hybridizing articles that have appeared in the ARS Journal. They have been about theories and the application of those theories in the development of hardy rhododendron hybrids. It was pointed out to me recently that none of these articles made reference to my own hybrids. This article is written for those who may have some interest in them.
        Edward Kennedy Ellington - the "Duke" - once said, "If it sounds good, it is good!" Regarding rhododendrons one might say, "If it looks good, it is good!"...but in the climate of Northeastern Pennsylvania one should add "but is it hardy?"
        My hybridizing started in the late 1960s and continued into the late 1980s. During that period I lived in southern Connecticut and eastern Long Island. In 1985 we moved to Houston, Texas, for business reasons, lived there "rhodyless" for twelve years, and upon retirement moved to Hamburg, Pennsylvania. I began over again - without an established garden and without even one rhody to stick in the ground. I literally built my garden - soil, etc., including some shade trees for my soon to be rhody garden. The photo of part of my garden shows a few sunburst locust trees. They provided a source of "almost instant" dappled shade so necessary for elepidote rhodies in the Northeast. Without them many of my newly planted hybrids would have fried during that first summer. The trees are not only beautiful; they are fast-growing, wide-spreading and non-invasive. I have rhodies planted within one foot of the tree trunks. I recommend them.

Garden View
Garden View.
Photo by Dennis Mac Mullan

        Years ago I gave cuttings and small plants of many of my hybrids to people who admired them. Upon my return to the rhody world many of these people contacted me and offered either cuttings or plants of these same hybrids. Not only did they still exist, but they had done rather well. Thankfully "give and ye shall receive" is still in effect.
        I planted the first few of my rediscovered hybrids in the fall of 1998. More were added over the next few years. I am now growing over twenty of my earlier hybrids. When the first of these set buds I realized that it had been over eighteen years since I had seen them in bloom! Upon reflection, two things were apparent: 1) These plants were resilient and hardy. They had survived some tough winters and hot humid summers without any pampering1; 2) They were considered attractive by those people growing them (or why would they propagate these hybrids?)2
        So, here are some of my better efforts. For those who are interested, the parentage of each is listed at the end of the article.
        1. 'Mac's Magic'. Large flowers (4"), full truss. Medium, clear yellow. Large, fir-green glossy leaves. Low growing (2' at 5 years) and widely spreading.

R. 'Mac's Magic'
'Mac's Magic'
Photo by Dennis Mac Mullan

        2. 'Mac's Orange Crush'*. A combination of medium orange and reddish orange. Takes considerable summer sun without wilting or showing undue stress.
        3. 'Thunderclap'*. A hardy (-12F) deep red. The use of 'The Honourable Jean Marie de Montague' and Kilimanjaro Group aid in reducing the "blue" influence of 'Mars' (which was utilized for hardiness). Tall and open-growing.
        4. 'Tuscan Sun'*. Overall my best yellow so far. Large flowers (5"), full truss of medium/deeper yellow. Hint of apricot in the throat. Well branched. 5' x 5' at 6 years. Good glossy foliage. A "good-doer."

R. 'Tuscan Sun'*
'Tuscan Sun'*
Photo by Dennis Mac Mullan

        5. 'Billy Wilder'. A good orange. I considered naming it "Some Like It Hot" for the Marilyn Monroe, Tony Curtis, Jack Lemmon film comedy - directed by Billy Wilder - but the name seemed too long. As a brief aside: you may recall that Marilyn played a band singer named Sugar Kowalczyk. In one scene she is to knock on a hotel room door. A voice on the other side says, "Who is it?" Marilyn had just one line. She is supposed to reply, "It's me, Sugar." For sixty straight "takes" she replied, "Sugar, it's me!" Before the sixty-first take someone posted a note on the door - at eye level - with the correct line written on it. Marilyn walked to the door, saw the note and, screaming, ran from the set. Billy Wilder waited for half an hour and then went to Marilyn's dressing room. "Marilyn," he said. "Just calm down - relax - and don't worry." In that guileless, wispy voice she sometimes used, Marilyn, with wide-eyed innocence, said, "Worry about what?"3 A hot clear orange that is low-growing, hardy, and appears to be able to withstand considerable sun and heat. A rarity in this color.
        6. 'Polperro'*. A blend of deep pink, shell pink and light pink. A nice effect. Very tall, full truss.
        7. 'Speckled Honey'. Many people say this is their favorite among my hybrids. It is attractive. Large flowers have a peachy, honey color with heavy speckling in the corolla throat and spraying to the petal edges on the upper part of the flower. The photo describes it best. Big truss. The plant is somewhat open-growing.

R. 'Speckled Honey'
'Speckled Honey'
Photo by Dennis Mac Mullan

        8. 'Lovely Leslie'. Named for my wife. 4 feet at ten years. Very floriferous. Slight resemblance to 'Percy Wiseman' but handles the summer heat much better. Bushy. Another "good-doer."

R. 'Lovely Leslie'
'Lovely Leslie'
Photo by Dennis Mac Mullan

        9. 'Mac's Solar Surprise'. Varying shades of yellow and peach give a multi-toned effect. Reliable bloomer with flat-faced flowers. Seems to like summer sun (odd for a yellow).

R. 'Mac's Solar Surprise'
'Mac's Solar Surprise'
Photo by Dennis Mac Mullan

        Other of my hybrids which seem to be growing successfully in Hamburg are: 'Howard Kline', 'Hollybrooke'*, 'Mac's Moonbeam'*, and 'Mac's Sunspot'*.
        I have tried to include hardiness on at least one side of each cross. Where possible (keeping in mind the goals of good clear color(s), truss shape and plant habit). I try to include some hardiness on both sides. This, unfortunately, is not so easy to do (and still maintain a high degree of color).
        My old friend Jack Rosenthal once told me, "If you make a cross with a hardy plant that lacks strong color and a more tender plant that has strong color, the seedlings with the most color will be the most tender; those with less color will be more hardy." I don't know if there is genetic foundation for his theory, but I suspect that it is closer to being right than wrong.
        Has anyone noticed that hybridizers rarely - if ever - document their failures? Crosses that do not pan out - for whatever reasons - should be noted and the information shared. It may help eliminate similar efforts by others. David Leach did something like this involving crosses he made with Rhododendron maximum to show why it is a bad parent. Just a thought.
        Hybridizing (when factoring in hardiness and heat tolerance) is a continual learning process if your goal is to develop truly "special" rhodies. One does one's best - genetically speaking - and must then trust that the hybridizing gods will bring you some luck.
        I am in my 74th year and I intend to "keep on truckin"! I am currently working to improve some of my existing hybrids - better plant habit, tighter, larger trusses There is plenty of work to do. Perhaps Jim Barlup has a suggestion - or two. Stay in touch.

Parentage of Hybrids
'Billy Wilder' - 'Goldsworth Orange' X (['Inca Gold' x R. degronianum ssp. yakushimanum] x ['Catalgla' x R. dichroanthum])
'Lovely Leslie' - 'Hello Dolly' X (['Inca Gold' x R. degronianum ssp. yakushimanum] x R. wardii, KW 4170)
'Mac's Magic' - ('Kruse's Big Cream'*4 x R. dichroanthum) X ('Janet Blair' x 'Seattle Gold')
'Speckled Honey' - 'Janet Blair' X ('Apritan' x 'Seattle Gold')
'Tuscan Sun'* - ('Goldsworth' Orange' x [R. degronianum ssp. yakushimanum x 'Goldsworth Orange']) X ('Big Cream'* x 'Golden Star')
'Thunderclap'* - ('Mars' x 'The Honourable Jean Marie de Montague') X ('Mars' x 'Kilimanjaro')
'Hot Stuff'* - 'Mary Belle' X 'Wizard'
'Howard Kline' - ('Coral Velvet' x R. wardii, KW4170) X 'Wizard'
'Mac's Orange Crush'* - ('Coral Velvet' x Goldsworth Orange') X ('Catalgla' x 'Goldsworth Orange')
'Mac's Solar Surprise' - 'Janet Blair' X ('Pacific Gold' x 'Phipps Yellow')
'Polperro'* - ('Mars' x 'The Honourable Jean Marie de Montague') X (R. degronianum ssp. yakushimanum x 'The Honourable Jean Marie de Montague')

1 I aim for winter hardiness of -10F to -15F (in spite of all the global warming talk.)
2 Most are still growing in areas around Stamford, Norwalk, Westport and Greenwich, Conn.; Long Island, NY; and northeastern Penn.
3 As related by Billy Wilder in an interview.
4 'Kruse's Big Cream' - 'Catalgla' X 'Crest' (a Ray Kruse hybrid)

* Name is not registered.

Dennis Mac Mullan is a member of the Valley Forge Chapter.


Volume 61, Number 3
Summer 2007

DLA Ejournal Home | JARS Home | Table of Contents for this issue | Search JARS and other ejournals