Let's Talk Hybridizing: Breeding
for Dwarf Elepidotes in Nova Scotia
Halifax, Nova Scotia
The recent article "Hybridizing for Dwarfness" by Allan and Shirley Anderson (JARS fall 1999) certainly had us sitting up to take notice. Over the last fifty years rhododendron breeding in Maritime Canada has produced some fine dwarfs although the mission at the outset was to simply produce good hardy plants for conditions in our area. Using plants considered to be the best bets - Rhododendron aureum, dwarf R. brachycarpum and R. catawbiense v. compactum - our pioneer hybridizers bred some good, compact, slow-growers as an added bonus. It would seem that a brief summary of what's happened here in Nova Scotia since 1950 is long overdue. In this article we will look at dwarf elepidotes; the hot topic of what is "dwarf" will not concern us except to say a R. forrestii Repens Group hybrid 7cm (3in) tall x 2 m (6ft) across and an elepidote hybrid 2m (6ft) high in forty years will both be considered dwarf or slow growing. We will follow up with a look at the new directions we have taken in the last fifteen years.
Rhododendrons in 3D
Dreams, Dwarfs and Delusions
Climatically our situation on the Nova Scotian coast - windswept and foggy, a fair assessment - is very much different from eastern North America. At 45° latitude it is a trying climate, and, stuck out in the North Atlantic as we are, the ocean influences every aspect of life. To the south, the Gulf Stream tempers the cold a bit and its closer cold water return, the Labrador Current, flowing west along our shores, cools and produces our famous persistent fogs. To our west, the Bay of Fundy moderates the scythic continental winter winds which accompany our worst cold. The Fundy rises and falls tidely an incredible 50 feet (15m) twice a day, thereby staying somewhat warmer than might be expected - and it's another fog producer. To our northeast, the Gulf of St. Lawrence, the warmest summer saltwater north of Cape Hatteras, gives us comfortable summers and falls but delays our springs as it stays ice-packed as late as April or early May!
In winter, our coastal Zone 6 is alternately very wet and very cold and snow cover is unreliable. The cold of January, February and early March can at times be brutally Arctic-like and persistent. Winter temperature fluctuations are precipitous and Halifax, the capital city where I live, chalks up more freeze/thaw cycles than any other Canadian city. A local saying sums it up: "If you don't like the weather out the front door, look out the back door." Halifax also records a dizzying 100 days of fog per year. Multi-directional gale-force winds are frequent and our thin acid mineral soils can stay frozen well beyond root depth into April and sometimes May. Plants in this frozen soil, while air temperatures still hover at or below freezing, can incinerate under the brutally intense March sun. With a painfully cold spring damaging late frosts are very rare, at least in my immediate area along the coastal mainland. On the plus side our cool summer nights, frequently foggy evenings, cool soil and brief warm period are big assets which help us to grow a surprising range of species and hybrids. Adaptability to these formidable climatic vagaries is our prime breeding goal.
The four Atlantic provinces showing the obvious zonal effect of the wild
Map courtesy of Agriculture Canada
Fortunately Nova Scotian rhododendron breeding and collecting started in earnest fifty years ago and we now have a wealth of dwarfing material at our disposal through the generosity of our foremost breeders. In the early 1950s, Dr. Donald Craig and the late George Swain voluntarily started a breeding programme at the government's Kentville Research Station in Kentville, Nova Scotia. At this colder site in the fertile Annapolis Valley thousands of seedlings were field grown without protection. Only a handful were later named and registered. Dr. Craig, now in retirement, continues breeding at his colder inland garden.
Craig has found some surprising sources of dwarfness in his programme. For him Shammarello's 'Besse Howells' has attributes worthy of consideration - hardiness, compactness and semi dwarfness. Out of eighteen yak** x 'Besse Howells' seedlings he has four selections. Similarly, thirteen of ninety-five seedlings of a cross of 'Minas Rose Dawn' x 'Besse Howells' are on trial including his best red to date. His 'Minas Rose Dawn' is ('Nova Zembla' x yak) x ('Elizabeth' x yak) and 0.9m (3ft) high and 2.75m (9ft) wide in twenty-eight years. SEL 75-31, a 1971 cross of ('Gable's Red Head' x yak) x ('Catalgla' x 'Elizabeth') has a nice compact truss, the colour of 'Nova Zembla', but measures only 0.9m (3ft) high x 1.4m (4.6ft) wide in twenty-eight years; it will surely be of use.
His dwarf plants of note follow:
(aureum x forrestii Repens Group) F2. 0.25m (0.8ft) x 0.7m (2.3ft) in nearly 35+ yrs., rose red, a staminoid double but pollen can be found. A Hobbie cross at the Station still has uses in breeding for reds.
brachycarpum, a creeping form under 0.3m (1ft) has been at KRS for many years.
catawbiense v. compactum x williamsianum (now 'Minas Grand Pré') A KRS introduction. 1m (3.3ft) in twenty years, pink, compact and a terrific performer. This is now available from Brigg's Nursery. I have sibbed 'Minas Grand Pré', put its pollen on williamsianum and done the reverse cross - all are similar and dwarfer and getting closer to the delectable but decidedly tender williamsianum.
R. 'Minas Grand Pré' growing in a Nova Scotian coastal garden.
A Craig/Swain hybrid.
Photo by John Weagle
('Bellefontaine' x 'Goldsworth Yellow') x degronianum (2 selections). 0.5m (1.6ft) high x 1.5m (5ft) wide at 20+ yrs., yellow and pink combo. This last hybrid has produced some fine dwarfs when it was combined with Steele's best yellow BPT#80-5: (['Bellefontaine' x 'Goldsworth's Yellow'] x degronianum) x (aureum x 'Prelude'). Several compact mounds sporting dark yellow flowers are now on trial.
(['Bellefontaine' x 'Goldsworth Yellow'] x degronianum).
Donald Craig has used this early hybrid to produce better compact yellow.
Photo by John Weagle
Cpt. Richard M. Steele is well known in the rhododendron world. A disciple of two rhododendron legends of the twentieth century, Joseph Gable and T. Hope Findlay, he started breeding and collecting in the 1950s and has now amassed a collection of thousands of plants covering more than thirty open and wooded acres at Bayport Plant Farm near Lunenburg, Nova Scotia. Steele's breeding work is of the greatest importance for the future. His work is so multi-faceted that it is well beyond the scope of this article. It will be no easy task to assess the countless plants on trial. Seed growers will recognize "Blwd"/"Boulder-wood" and "BPT"/"-Bayport" as well-known prefixes to his plants. A rich bank of dwarf material is available to local breeders including these important crosses:
aureum x 'Binfield'. 1 m+ (3.3ft) in a fair amount of shade and a valuable source of yellow genes.
aureum x 'Bosutch'. 1m (3.3ft) high x 1m (3.3ft) wide in 35+ yrs., early whites and a few pinks.
aureum x 'Catalgla'. 35 yrs +, 1 m (3.3ft) high x 1.5m (5ft) wide, early whites and creams.
aureum x lanigerum 'Round Wood'. One red dwarf, the rest ivory/cream, very low and early.
aureum x 'Prelude'. 35 yrs +, 1.25 m (4ft) high x 1.5 m (5ft) wide, good early yellows, BPT#80-5 the best and yellowest and a useful breeding plant. BPT#82-1 has a touch of orange in bud.
'Blue Peter' x chamaethomsonii. A bizarre cross, inexplicably bright red and very dwarf.
brachycarpum (low form). Many nice old plants under a meter.
(brachycarpum x wardii)F3. 1m (3.3ft) high x 1.5m (5ft) wide in 35+ yrs., various colours, one with narcissus-like flowers with fused stamens.
(brachycarpum x williamsianum)F3. 1m (3.3ft) high x 1.5m (5ft) wide in 35+ yrs., whites and pinks, compact.
yak x Moonstone Group. 70cm (28in) high x 1 m (3.3ft) wide in 35+ yrs., pale yellow, one very tight plant.
yak x (Repens Group x Barclayi Group). 20+ yrs., very dwarf and prostrate in full sun, quite red.
Cpt. Steele spent a good deal of time in the '50s with T. Hope Findlay at Windsor Great Park. Findlay was one of the legendary plantsman of the century and Steele says his advice was invaluable. One point Findlay stressed was one to be heeded by all hybridizers: "Always go back to a hardy species when your hybridizing gets complex." This, he reckoned, would help stabilize the results and give a degree of predictability. The payoff is twofold - hardiness is more predictable and population requirements are indeed somewhat reduced. Steele follows this principle and I too try to avoid using complicated hybrids on both sides of my crosses - often hard a difficult thing to do.
Steele at 80+ is having great fun with the new possibilities. A recent cross of ('Elviira'* x [calophytum x Repens Group]) has produced plants with both large and small leaves. It is believed the bushy little plants that are now being propagated will remain dwarf. His very good yellow (aureum x 'Prelude') BPT #80-5 has been crossed with Kentville's (aureum x Repens Group)F2; the youngsters youngsters are just at bud stage and everyone is holding their breath. During every visit to Bayport we find plants or a line of breeding completely unknown to us. Steele sums up his objectives thusly: "Although I personally greatly enjoy all aspects of the bloom and new growth each year, our prime target is stud potential in the future: hardiness, durability, beauty and longevity." A study group is now documenting and assessing this great legacy.
Dean Barber's (aureum x maximum) F2 growing near
Peggy's Cove, Nova Scotia. A stepping stone to
produce better habit and foliage for windy sites.
Photo by John Weagle
Walter Ostrom has gardened for thirty years in the windy fog belt near Peggy's Cove, N.S. He has collected and bred a few plants of interest to us. His (maximum x aureum) F2 from Dean Barber is a tight compact plant, lavender pink, extremely bushy and under 0.5m (1.6ft) in 20+ years - an invaluable lesson for anxious hybridizers in the merits of going to the F2 generation. Granted this is not a finished plant; the truss is loose and the colour poor but these faults can easily be remedied. We have many plans for this plant including hitting it with insigne. Walter has a reliable aureum which is both prostrate and the darkest yellow we have seen. Evelyn (Jack) Weejes gave this plant to Walter and says it was probably one she grew from seed. Here we know it as aureum 'Miss Jack', a tribute to this phenomenal plantswoman who opened our eyes to the possibilities of lepidote species here - a major turning point for rhododendron culture in Nova Scotia. An Ostrom cross of brachycarpum x aureum is cream, under 25cm (10in) and with good hardiness genes; it has been crossed with some of our better oranges and yellows. His exciting new cross ([brachycarpum x aureum] x caloxanthum) bloomed recently and is an emphatic yellow with large open-faced flowers and perfectly compact. It is a very cheery little thing and we trust this cross will stimulate him to return to breeding. Its pollen was used on 'Elviira', 'Vinecrest', 'Yellow Gate' and on a delightful new hybrid with orangey/yellow bells (williamsianum x caloxanthum). Seed of these will appear in the 2001 ARS Seed Exchange. In the garden are some very beautiful, dwarf yaks from Serbin's collected wild seed including a form which stays compact and buds reliably in dense shade - aptly nicknamed 'Shady Lady'*. These yaks, most regrettably, we have neglected in our breeding to date.
The late Dr. Joe Brueckner did pioneering work in the 1960s and 1970s in very much colder Saint John, New Brunswick, using R. brachycarpum Tigerstedtii Group, R. dauricum v. sempervirens from Lake Baikal and a tall form of R. lapponicum from Great Slave Lake. He continued his work in Mississauga, Ontario, where summers are very much warmer. These are but a few of the promising dwarfs from the Brueckner programme:
aureum x campylocarpum. 0.3 m (1ft) high x 2m (6.6ft) wide.
(aureum x nikomontanum) x williamsianum, dwarf.
'Catawbiense Album' x aureum, dwarf. 'Lionel's Red Shield' ('America' x 'Carmen' [Rothschild]). 25cm (10in) high x 0.8 m (2.6ft) wide, red but a tad tender.
nikomontanum x Repens Group, prostrate red and also one emphatically variegated plant.
various brachycarpum x sanguineum hybrids (using chiefly Rödhätte), under 0.75m (2.5ft) all with magnificent dark, clean and very distinctive foliage.
many hardy williamsianum hybrids with brachycarpum Tigerstedtii, catawbiense and maximum. The latter maximum x williamsianum gave a few sturdy williamsianum look-alikes.
Brueckner's intense focus was on hardiness; he had battled the brutal winters of New Brunswick and so zeroed in on brachycarpum and aureum. This was a sound plan and indeed visionary. His plants now give us an incredible tool to produce hybrids with greatly improved foliage and a wider colour range for the north. Our study group will begin testing almost 500 Brueckner hybrids for quality and adaptability. Many will no doubt be released eventually.
Our thrust since 1985 has been to introduce fresh species and "new generation" material from other collectors and hybridizers into this rich bank of local material. Progress has been slow but steady as you will see in Part II.
* Name is unregistered.
** yak: R. degronianum ssp. yakushimanum.