QBARS - v30n4 The Hardgrove Rhododendrons

Richard Murcott, East Norwich, New York
From a paper given at the 1976 Annual Meeting in Valley Forge, Pennsylvania.

Let me say, in all candor, that I thought a talk about the Hardgrove rhododendrons would be quite an easy task. After all, I had known Don, had seen his garden, was familiar with some of his named cultivars, and had even purchased a plant from him when he was breaking up his garden. I casually started to talk to some people who had been friendly with Don and I was able to see a copy of Don's stud book. I began to discover that what I knew about him and his plants was just a tiny tip of an enormous iceberg.
What is common knowledge of his hybrids is derived from the five named cultivars sold by Sid Burns and now his son Tom. Four of these are yellow, of one shade or another, and the fifth, red. So almost everyone equates Hardgrove with yellow rhododendrons. But actually Don was interested in every color and was also very active in hybridizing the lepidote rhododendrons. But what is most interesting of all is that now, 12 years after he stopped and disbanded his garden, we are discovering new hybrids of his, some of which could be his finest creations.
Before I talk about his hybrids, let's investigate the climate of Don's garden. Don was a Long Island hybridizer and it is important for you to know a little about the climate of the island so you can understand the hardiness of his plants. There are two climatic zones on the island; a warmer zone near both the north and south shore and a central colder zone.
Don's garden was in the milder zone, a maritime zone influenced by the Atlantic Ocean. His garden also contained high oak trees for shade and wind protection. I would expect plus 5°F. to be an unusually cold temperature, reached perhaps once a winter. There would be exceptions, of course, where the low temperature would be less, but generally, that would be his lowest winter temperature.
Don started hybridizing in 1945. Early articles in "The Rhododendron Yearbook" and "Quarterly" indicated the great deal of thought that he put into hybridizing. He was quite interested in genetics and his close associations with Guy Nearing, his teacher, is evident in the crosses he made and proposed.
Through his writings and correspondence he was able to get pollen from advanced hybridizers and growers in this country and England. Indeed, pollen of R. fictolacteum , sent to him by Guy Nearing who was touring England, was used to create 'Hardy Giant', by using hardy R. fortunei as the seed parent. Don made the cross and sent the seed to Nearing, who passed the seed on to the Knippenbergs who grew them and named one.
The lepidotes, for which Don is not now known, interested him greatly. Many lepidote crosses were made - with much success. Some of the best lepidote hybrids are 'Spring Song' and an unnamed white, carolinianum x moupinense . 'Spring Song' is one of his early selections (selected in 1948) and it has the same parents as 'Mary Fleming'; ( racemosum x keiskei ) x keiskei ). It is similar to 'Mary Fleming' but with better color. The carolinianum x moupinense clone is the one that Sid Burns has. Don had many plants of this cross but the others that I know of either petered out or were of no special interest. The Burns plant is everything you might want: pure white, very hardy and a full, rounded truss with large florets. It blooms very early, about 10 days after mucronulatum on a dense, compact plant.
'Star Sapphire' is carolinianum x augustinii . It is a lovely blue but the plant doesn't seem particularly vigorous. It's not a good doer in an exposed location. Perhaps some high shade would help it.
'Starlight' is carolinianum x leucaspis . Don liked this hybrid a lot but I have not been able to find the plant. I don't know if it exists.
In 1964 Don gave his only lecture to the New York Chapter. The transcript of that talk was printed in the October, 1966 Quarterly. Advice given about breeding lepidotes, learned after much trial and research, was spelled out here he explained how to cross the hardy carolinianum with the beautiful, tender, large flowered lepidotes. The method is to use the Boothii series as a bridge. Since the Boothii series will cross with the large flowered lepidotes and also carolinianum , he crossed a hybrid of a Boothii and a large flowered lepidote onto carolinianum . Don used pollen of 'R. W. Rye' from England to do just that. The cross took and the seed sprouted but were then lost due to lack of care.
Don was hybridizing for all colors in the elepidotes. Several whites have been selected, but the white that Don liked the best, his H53-6, died after it was moved out of his garden. Don didn't purposely hybridize for white, the plants that bloomed white in purchaser's gardens were mistakes! Three whites have been selected by their new owners and are listed in the appendix.
Hardgrove's best pink was 'Pink Symphony' - hardy fortunei x "Diva". Don liked this plant, but I don't know if it is still alive.
His named red, 'Anne Hardgrove', is quite a spectacular flower. It is 'C. P. Raffil' x 'Moser's Maroon'. A late bloomer of intense red, it has a very leggy plant habit and should be planted in the rear of a bed to allow the blooms to come up high. 'Virginia Hall' is a very early selection of his: H46-6. It is similar to 'Beatrice Pearce', a Nearing cultivar of the same parentage, but 'Virginia Hall' has the attribute of ease of rooting, something 'Beatrice Pearce' doesn't have.
Now for the yellows. The key for Don in developing yellow hybrids was the hardy fortunei that he received from Nearing. Guy and Joe Gable spent many years growing on fortunei seedlings, crossing the hardiest, and growing the seed on. After three generations, and some 21 years, they had a hardy race of fortunei . Don had one of these and used it extensively in his yellow hybrids. It seems as though the hardy fortunei would accept the yellow color of the pollen parent yet contribute its hardiness and floret size to the offspring (a little fragrance too).
The cross that was his most successful was: hardy R. fortunei x ( wardii x dichroanthum ). This was an astounding cross, yielding many plants of every color from white to peach to copper. In addition to the named clones, several numbered ones exist. One of these H58-6, I especially like as it has very large florets of medium yellow with a light pink on the edge of the corolla. In my garden, the plant grows much wider than high. Many seedlings were named from this cross. One, 'Leeanne Hardgrove' won a P.A. at the 1962 New York Chapter show. This was the first East Coast rhododendron ever to get that award. After it blooms, H62-5 bloomed. Don named the later bloomer 'Barbara Hardgrove' and thought it better than 'Leeanne Hardgrove' P.A.
The seedling with the most color, and the one Don thought was the best, is 'Donna Hardgrove'. It blooms somewhat early, May 9th this year, and is a blend of orange, yellow and red. You can read Don's description of it in the listing in the appendix.
Another cross in which hardy fortunei was the seed parent and produced yellow offspring was hardy fortunei x croceum . The best seedling of that cross was named 'Golden Star'. It makes quite a show in the garden.
Of the yellows, I've only mentioned a few out of so many.
Another hardy fortunei cross that produced many very good offspring used pollen from 'Purple Splendour'. Don was astounded by the floret size of the seedlings. He numbered several and named one. These have also proven to be very hardy, many of them growing out in the full sun virtually unprotected. All shades of lavender exist with small to large, deep-purple blotches or spots on the upper corolla.
Even though many of Don's best plants are now growing in the gardens of New York Chapter members, most of his plants have been lost. In 1964, Don had three months to dispose of his entire garden. A buyer had to be found quickly who had the ability to dig thousands of 4-5 foot rhododendrons in a very short time. Obviously, this wasn't a task for amateurs. A commercial nurseryman bought the bulk of the garden and Don distributed most of his best plants to members. I am sorry to say that at least 95% of Don's plants have died.
Some members purchased un-bloomed seedlings, selecting plants by foliage and general growth characteristics. Some of these have turned out to be very good and have been unofficially named by their owners. I am including a list of these in the appendix.
Don felt that he had created the finest group of rhododendron hybrids for Northeast gardens. I recommend them to you for your trial to see if, under your garden conditions, they will perform as well as they did for him.

Plants named by Don Hardgrove
'Anne Hardgrove' - H56-22
'Barbara Hardgrove' - H62-5 ( fortunei x ( wardii x dichroanthum )
'Crimson Star' - Britannia x ?
'Donna Hardgrove' - ( fortunei x ( wardii x dichroanthum )
'Firelight' - H58-10
'Glow Light' - H60-4
'Glowing Star'
'Golden Glow' - H59-1
'Golden Star' - H56-?
'Halolite' - H58-14
'Hearthfire' - H60-5 - 'Atrier' x 52-27
'June Rhapsody' - H58-17
'Lavender Lace' - H61-2
'Leeanne Hardgrove' P.A. - fortunei x ( wardii x dichroanthum ) - H62-2
'Lemon Chiffon' - H60-2
'Little Flame' - H58-3
'Morning Star' - H56-?
'Painted Star' - H52-33
'Pink Symphony' - H57-15
'Radiant Star' - H58-12
'Royal Star' - 'Moser's Maroon' x ?
'Roxanne Hardgrove'
'Salmon Beauty' - a Dexter seedling
'Spring Song' - ( racemosum x keiskei ) x keiskei - H48-1
'Starlight' - carolinianum x leucaspis
'Star Sapphire' - carolinianum x augustinii
'Virginia Hall' - H46-6

Hardgrove Plants Selected By Others as Outstanding Or Named by Others
H59-2 - Probably catawbiense compactum x 'Venator'
Deepest Yellow - fortunei x ( wardii x dichroanthum ) H62-3
DH8 - ('Tally Ho' x 'Margaret Dunn') x 'Meadowbrook'
DH10 - ('Fabia' x Glass White)  x ( decorum x campylocarpum )
H64-1 - (( catawbiense compactum x ( lacteum x 'Mary Swathling')) x ( campylocarpum x 'Penjerrick')
Mid-May White - unknown, to be named: May White
Sister of 'Golden Star' - fortunei x ( wardii x dichroanthum ) to be named 'Amazement'
'Shady Lady' - unknown parents
Mid April White - unknown parents to be named: Star of Spring
('Fabia' x Glass White) x 'Leddy Edwards' to be named: Copper Cream
('Fabia' x Glass White) x 'Golden Star' to be named: Shooting Star
H58-6 - fortunei x ( wardii x dichroanthum )
'Kathryn Reboul' - spinuliferum x racemosum F2
'Jean Baptiste Reboul' - fortunei x ( wardii x dichroanthum )
H58-8 - fortunei x ( wardii x dichroanthum )
H64-2 - fortunei x 'Purple Splendour'
Seedling of 'Painted Star'
carolinianum x moupinense
H58-9 - fortunei x ( wardii x dichroanthum )
DWF# 1 - fortunei x (wardii x dichroanthum )
Williamsianum hybrid #2
Williamsianum hybrid # 1