JARS v9n1 - The Delp Hybrids: Part I, A Passion for Rhododendron Hybridizing

The Delp Hybrids: Part I, A Passion for Rhododendron Hybridizing
Dr. Homer Salley
Danville, Kentucky

When Weldon Delp stopped making crosses in 1993 a long era had ended in the history of rhododendron hybridizing. Beginning in 1947 with the selfing of the hardy red hybrid, 'Dr. H. C. Dresselhuys', one seedling was selected from the many and later named 'Tower of Power'. These dates, 1947-1993, mark the years of the beginning and ending of a career as a nurseryman that lasted 46 productive years.

Weldon Delp makes a cross.
Weldon Delp makes a cross.
Photo by Homer Salley

Few nurserymen ever created so many or sold so few. Delp's Crystalaire Rhododendron Foundation accepted gifts but did not sell plants. At one time Weldon's mother, Christina Delp, sold a few unnamed seedlings, but she was discouraged in that practice. She was very pleased once when she got $20 for a plant, then found out later it was being saved for breeding purposes! Called "Mama" by all the family and friends, Christina was a lovable, untiring, faithful greenhouse worker for many years. Seedlings from a cross had to have labels giving the parentage as identification. While writing out the cross [('Pygmalion' x haematodes ) x yakushimanum , Exbury form], she was inspired to use the name 'Weldy'; that was a lot shorter. Mother Christina passed away in 1987, at the age of 87.

Weldon's wife, Ginny Delp, did nearly all the naming after that; with her computer, beginning in 1985, she entered names, colors, parentage, foliage descriptions, sources of seed and pollen. "Coloring” meant using the color chart of the Royal Horticultural Society and selecting the correct color number for flower buds, and then the size, shape, and color of the fully opened trusses of flowers, all these requirements for the registration of named hybrids. (Hardiness ratings had to wait until field testing was done over a period of years.) Her own particular genius was the coining of names not previously in the International Rhododendron Register. Her accepted registered names now number 389: altogether she has originated 1,286 rhododendron names. These numbers must even challenge those of the prolific German hybridizer, Hans Hachmann. (See Delp hybrid registrations published in each Journal ARS, beginning in 1992. See also the annual supplements to the Register published by the Royal Horticultural Society, London.)

An Ohio nurseryman who has been growing Delp hybrids called to report an incident that occurred while on tour in Scotland. He had visited a nursery there where he was told that the Delp hybrids were ineligible for registration because of their lack of adequate testing. When the incident was described to the International Registrar, Dr. Alan Leslie, Royal Horticultural Society, Wisley, a reply was sent to the Ohio nurseryman. "I understand that you had been informed that many Delp hybrids were ineligible for registration having not been adequately tested. This is not true: for two reasons. Firstly a good number of them have been grown by other people in other areas. Secondly and more importantly this is not a condition or prerequisite for registration. It is of course highly desirable that raisers should seek to name (and then register) only the best and most distinctive new plants. And admittedly many growers do rush in breathless with excitement at their latest novelty which on mature reflection turns out to be no great improvement on others or hardly distinguishable. However, the point I want to make is that it is up to the originator to make the decision as to what is worth naming, not the International Registration Authority. We are there to deal with all cultivars that have been named; we do not sit in judgment over quality and distinctness, but provide a service in name regulation and, through eliciting data on parentage and characteristics, a reference for anyone interested. We strongly encourage testing and a conservative approach to naming but once a plant: named we want to know about it. If I can be of further assistance, please do not hesitate to contact me here at Wisley." One might wonder if the Registrar could have heard a recording of a Delp illustrated lecture, given before his hybrids had names, identified only by their parentage!

Weldon Delp Chronology

• Born Feb. 20, 1920.

• Graduated Universal Chiropractic College, June 1941.

• Married Virginia Porter, July 31, 1941.

• Military service: Medical Corps, 1943-46 (France, England, Scotland).

• Two daughters born: Judy, Jan. 7, 1943; Joyce, Aug. 2, 1949.

• Nurseryman, Harrisville, PA, 1947-93.

• First hybrid cross ('Dr. H. C. Dresellhuys' selfed) 1947.

• Operated bowling lanes, 1963-1987.

• First named hybrid, 'Christina Delp', 1965.

• Featured in American Nurseryman, May 15, 1974.

• First hybrid 'Christina Delp' in color, Dr. Franklin West's book, 1978.

• Bronze Medal, Great Lakes Chapter, 1979.

• Toured England (pollen collecting not authorized!) 1981.

• Crystalaire Rhododendron Foundation, 1982-93.

• Ginny Delp began naming and "coloring," 1982.

• Helped organize area study group, about 1983.

• 'Weldy' named by mother Christina, 1983.

• First commercial introducer, Nick and Neala Anastos, 1984-87.

• Distributed growing mix formula (often revised) 1985.

• Ginny gets computer, 1985.

• Gold Medal, American Rhododendron Society, 1986.

• First complete published hybrid record, Salley/Greer, 1986.

• Awarded Life Membership, Rhododendron Society of Canada, 1987.

• Described method of multiplying terminal shoots, 1987.

• Ginny receives award from Azalea Society of America, 1988.

• Second introducer, Bill Storms (Cardinal Nursery) 1987-93.

• Paul James began collecting all available Delp hybrids, 1988.

• Greenhouse burned and rebuilt, 1989.

• Second published hybrid record, Salley/Greer, 1992.

• Official registrations entered in large numbers, 1992.

• Converted operations from hybridizing to propagation, 1994.

• Daughter, Joyce, builds stock for retail sales, 1994.

Weldon Delp did not really retire as a nurseryman in 1993, because he then started teaching his daughter, Joyce Harris, how to propagate cuttings of the many hundreds of his hybrid creations. In the same greenhouse in Harrisville, Pa., where the hybrids were born, the massive task has begun of producing for distribution small quantities of the hugh number of named, registered hybrids and of those not yet registered.

A Canadian nurseryman came and placed a $3,000 order. The taking of scions for rooting required locating those plants that had been given over the years to many friends and growers. Who had which ones? What hybrids were known to have survived conditions in a variety of places around the United States and Canada? Ron Fleeger brought cuttings to Weldon from Paul James. And there are hundreds of plants in the back woods at Harrisville with an abundance of terminal shoots waiting to be snipped and stuck in the propagating bed.

Delp's greenhouse in April
Delp's greenhouse in April.
Photo by Homer Salley

Growing also in the greenhouse are 500 tiny seedlings Weldon started from seeds of a selfed, West Virginia maximum species called 'Green Ma'.* Some of the seeds were treated 'with colchicine to attempt an increase of plant chromosomes. Selections will be chosen after flowering next spring. So his breeding and growing still goes on in smaller ways.

The Great Lakes Chapter formed the Delp Study and Preservation Committee with funds to support a serious work. Questionnaires were sent and replies came back with listings of 810 different Delp hybrids that were still alive. Thirty five locations reported: some had as few as one; some had as many as 25; some had up to 45, and one man, Paul James had 391! Charles Dagman, Colorado Springs, telephoned; one of his best rhododendrons, 'Genevieve Schmidt' was doing well at elevation 7,100! Another favorite of his was lepidote 'Blue Rascal'.*

The Delp study has produced more data: of the total 810 hybrids located, less than half, 389, have been registered. Of the 33 locations reporting, the average collection has 43 different, named Delp hybrids. In the severe climate of the Delp homestead there now live 347, which is exceeded by the number grown by the supreme collector, Paul James, with 391. Names of hybrids now considered to be extinct: 'Aflame', 'Airwaves', 'Alyssa Ray', 'Apricot Sunset', 'Colorburst', 'Delp's Celebrity', 'Heap Big Indian', 'Jennypoo'*, 'Leap Year', 'Magenta Madness' 'Microflare'*, 'Tom Shirey'. A list is available of 29 registered Delp hybrids believed to exist but not yet located. (Do you have unreported, named Delp hybrids?)

The search for a well-endowed arboretum with a suitable location for a display garden of Delp hybrids ended when The Dawes Arboretum, Newark, Ohio, offered a formal agreement to the Delp committee. This garden began with a planting of 15 budded plants and a propagating bed with cuttings of many others. Director Donald Hendricks has requested the committee to send only named, registered plants. When asked how many rhododendrons the Arboretum could accommodate, his reply was "enough to color a landscape of 250 acres."

Tissue culture multiplication is being utilized with a very few plants: 'Angel Powder', 'Delp's Sunsheen'*, 'Pana', 'Hindsight'. Several others are being considered. Why had not distribution quickly followed the creation of new rhododendrons? Weldon was very skilled at propagation; however, his greater passion was hybridizing. With no thought of any financial return he often would spend $10,000 or more annually in the greenhouse. It was not physically possible to create a large number of new hybrids and at the same time do field testing by growing them on. He planted a few, gave away more than he kept. His talent was God-given, he felt, to create beautiful, hardy hybrids for the severe climate in west central Pennsylvania. If they would survive there in USDA Hardiness Zone 4, they should grow in a great many other places. The new hybrids not hardy there could serve gardeners in more moderate zones.

ARS Gold Medal Award

In the fascinating world of the genus Rhododendron, your achievements represent a quantum leap into the future. Your intensive research, innovative techniques, thorough analysis, and meticulous record keeping have advanced hybridizing and propagation by giant steps. Your ability to relate and communicate with others, your innate friendliness and generosity have broadened the horizon of rhododendrons for everyone. With grateful appreciation, the American Rhododendron Society's highest award, the Gold Medal, is given to Mr. Weldon Delp on the 24th day of May, 1986, Cleveland, Ohio.

Great Lakes Chapter Bronze Medal Award

Because of an unsurpassed love of the genus Rhododendron :

Because of consummate skill in all phases of rhododendron culture and propagation shared freely with seasoned veteran and novice alike:

And because of unfailing support of the Great Lakes Chapter of the American Rhododendron Society in a multitude of ways:

The Chapter gratefully presents the Bronze Medal of the American Rhododendron Society to that superb plantsman and fine human being, Weldon E. Delp. 1979.

Weldon's genius showed in his experimentation. Admirer George Gray said, "He carried his 'What if's' to completion and was a source of new information. The completeness of his documentation in all phases of his hybridizing activities is extremely impressive. And his best qualities are his generosity and helpfulness." Consider the creation of hybrids 'No Way'* and 'Ididit';* the former a cross between a lepidote and an elepidote done in collaboration with Dr. Doren Hinerman; a noted rhododendron geneticist said "no way" could such a cross be successful but rhododendron hybrid 'No Way' still lives showing results can come from time consuming patience. The azaleodendron 'Ididit' is an expression of satisfaction from crossing 'Caroline' with two azaleas, an extra effort that few would spend the time doing when poor results are the usual rule.

Several of Weldon's admirers have said his greatest creations are the triploid lepidotes ('Neat Feat', 'Has Pizzaz', etc.) which resulted from crosses of tetraploids with diploids. These lepidotes bloom early with the azaleas but are more hardy than evergreen azaleas. And you don't need to "dead head" them. They are sterile.

In cultural efforts two outstanding accomplishments are credited to Delp. In 1987 he announced the results of experimentation on the best method and timing for pinching to get maximum terminal shoots in order to avoid growing "leggy" rhododendrons. 1 Also a notable feat was getting flowers from seed in 16­-18 months. Flower buds can be set from seed in 14 months, then a month of cold treatment followed by a month of warming to open flowers. Toward the end of April the greenhouse is known as a place of great excitement, filled with glorious color from new hybrids flowering for the first time. Only about 2 percent of the seedlings are exceptional enough for Ginny to name and "color" them.

"If they are any good," Weldon would say, "the world won't let them die" - even if he did not grow them on for hardiness testing. For a while the late Bill Storms of State Road, N.C., was that "world" trying to multiply and distribute. At one time the wrong rooting hormone caused the loss of a greenhouse filled with fresh cuttings. But Cardinal Nursery issued a sales catalog, and Bill gave Paul James a "backup" for nearly every Delp hybrid. But that is a story for another time - the world out there that would not let them die. Bill and Paul were only two of the apostles that spread the good news.

Top-Rated, Delp-Raised Hybrids
(Delp crosses except as noted)

'Action Packed'** ('Wizard' x 'Cat's Pajamas'*)

R. 'Action Packed'
R. 'Action Packed'
Photo by Weldon Delp

'Angel Powder' ('Epoch' x white mucronulatum )

'Anna Delp' [('America' x 'Blaze') x 'Red Brave'*]; Fetterhoff cross

'Aunt Mildred' ('Mrs. Davies Evans' x 'Virginia Delp')

R. 'Aunt Mildred'
R. 'Aunt Mildred'
Photo by Weldon Delp

'Born Winner' [( maximum x yakushimanum ) x 'Adele's Vellow']

'Cat's Meow'** ('Rougemont'* x 'Fiery Orange'); Tom Ring cross

'Charlie Grystar'* ['Ronald Otto Delp' x ('Harvest Moon' x 'Ice Cube')]

'Chatterbee' ('Ben Moseley' x 'Besse Howells'); Hinerman cross

'Christina Delp' ('Catalgla', green-eyed form x 'Mrs. W. C. Slocock')

'Delp's Cindy Lou' ['America' x ('Mars' x red catawbiense )]; Fetterhoff cross

'Delp's Dream' ('Si Si'* x 'Serendipity')

'Delp's Quest' {[( brachycarpum x 'Crest') x 'Stokes Bronze Wings'] x 'Goldsworth Yellow'}

'Delp's Stardust'* ('Ronald Otto Delp' x 'Golden Star')

R. 'Delp's Stardust'
R. 'Delp's Stardust'
Photo by Dr. Tom Ring

'Delp's Sunsheen'* [('Sweet Lulu' x vernicosum ) x ('Nereid' x fortunei ssp. discolor )]

'Delp's Sweet Wendy'* ('Weldy' x brachycarpum as ssp. tigerstedtii )

'Doctor Tom Ring' ('Fireman Jeff' x 'Anna Delp'); Tom Ring cross

'Fiery Orange' ('Ginny Mae'* x 'Dead Ringer'*)

'Flawless'** ('Rocky Road' * x 'Rougemont'*)

R. 'Flawless'
R. 'Flawless'
Photo by Weldon Delp

'Frosty Pink' ('Achiever' x 'Gable's 'Pioneer')
'Genevieve Schmidt' ('America' x yakushimanum )

'Ghost' [( maximum x yakushimanum ) x maximum )

'Goody Goody Gumdrop'* (Vineland seedling - unknown x 'Calsap'); Al Smith cross

'Gosh Darn!' [F2 selection from ('Catalgla' x 'Mrs. H. R. Yates')]

'Great Genes'** [('Ruddy Red Max'* x 'Midsummer') x self]

'Handsome Ris' [F2 selection from ('Mrs. J. G. Millais' x 'La Bar's White')]; Fetterhoff cross

'Has Pizzaz' ('Epoch' x 'Hi Tech')

'Helen Fleeger'** ('Abe Arnott' x 'Calsap')

'Hindsight' ['Epoch' x ('Achiever' x pemakoense Patulum Group)]

'Kickoff' ('Achiever' x mucronulatum )

'Major Harris'** ('Aunt Mildred' x 'Virginia Delp')

'Mikey'* ('Blue Peter' x 'Ice Cube')

'Neala'* [ aureum x ('Phyllis Ballard' x catawbiense 'Clark's White')]

'Neat Feat' (polyploid minus Carolinianum Group x 'Watchung'*)

'Oh My!'* ( smirnowii x yakushimanum )

'Pana' ('Oh My!'* x 'Red Brave'*)

'Picture Perfect'** ('Abe Arnott' x 'White Peter')

'Powerhouse' [('America' x 'Dr. V. H. Rutgers') x maximum ]

'Red Hot Mama' ['Anne Hardgrove' x (No.2 red x 'Delp's Cindy Lou')]; Tom Ring cross

'Renee Shirey' ('Caltwins #2'* x self)

'Ronald Otto Delp' ('Lodestar' x 'Mary Belle'); Hinerman cross

'Scampy'** {['Midsummer' x ('Lanny Pride' x 'Viet Vet'*)] x self}

'Shirlandy' {( brachycarpum x 'Crest') x ['Rocket' x ( yakushimanum x yakushimanum Exbury form)]}

'Si Si'** (yakushimanum x 'Gold Mohur')

'Sultry Peach'* ( aureum x 'Dead Ringer'*)

'Sweet Lulu' ('Gosh Darn!' x 'Dead Ringer'*)

'Testy'** ('Goody Goody' x self)

'Weldy' [('Pygmalion' x haematodes ) x yakushimanum Exbury form]; Kehr cross

'Winning One' ('Lodestar' x 'Mary Belle'); Hinerman cross

'Whopper'* ('Abe Arnott' x 'White Peter')

* Name not registered

** Registration pending

The information in this report and help in compiling it comes from the following: Everett Albyn, Allan Anderson, Virginia Delp, George Gray, John Heinze, Paul James, Jack Looye,­ Plant Name Registrar Jay Murray, Delp Study and Preservation Committee Chairman Dr. Tom Ring, Sally Salley and all who sent a list of Delp hybrids. The author kindly thanks these contributors.


1. Salley, H. E. The Children of 'R. O. Delp'. J. Amer. Rhod. Soc. 43: 1;­ 1989.

2. Salley, H. E.; Greer, H. Rhododendron Hybrids, A Guide To Their Origins. Portland, Oregon: Timber­ Press; 1986.

3. Salley, H. E.; Greer , H. Rhododendron Hybrids, Second Edition Portland, Oregon: Timber Press; 1992.

4. Swanson, P. L. The continuing search for northern-hardy rhododendrons. Amer. Nurseryman; May 15, 1974.

5. West, F. H. Hybrids & hybridizers, rhododendrons and azaleas for eastern North America. Harrowood Book; 1978.

Dr. Homer Salley is co-author of two editions of Rhododendron Hybrids and two volumes of Rhododendron and Azalea Research. He is president of his Bluegrass Chapter.

(Part II will more fully explore which Delp hybrids grow where with a close look at the collection of Paul James, Boones Mill, Va.)

1 "Pruning for Bushy Growth," Weldon Delp, J. Amer. Rhod. Soc. Vol. 41, No. 3, p. 137.
* Name not registered.
** Registration pending.