JARS v40n4 - The Vineland Connection: Part I

The Vineland Connection: Part I
A.W. Smith, Horticultural Technician
Horticultural Research Institute
Vineland Station, Ontario, Canada

The various articles that have been featured lately regarding breeding of deciduous azaleas have prompted me to report the results of some aspects of the azalea breeding program at the Horticultural Research Institute of Ontario, Vineland Station.
In the quest for petaloid or double form deciduous azaleas, most breeders have been using 'Homebush' or 'Norma' (Rustica Flora Peno hybrids) as seed parent. There is definitely nothing wrong with this approach as many excellent hybrids have been produced in this way. However, I believe the color range of new hybrids is limited due to the basic color of these two cultivars.
The year before I joined the staff at the Institute in 1974, I was introduced to Mr. Ken Duncan, who supervises the rhododendron and azalea plantings at Edward's Gardens Civic Center, Toronto, Ontario. These gardens are visited by people from all over the world and are noted for all phases of horticulture.
Ken and I placed an order with Knaphill Nursery of England to obtain the various double azalea forms that were available at that time. I was fortunate to acquire the cultivar 'Chelsea Reach' which was creamy white in color. This cultivar performed much better than 'Oxydol' and 'Silver Slippers', and always was a keen competitor for best in its class at various rhododendron flower shows.
It was during seed harvesting time in late September that "Mother Nature" gave me a firm prod while I was standing before 'Chelsea Reach'. The plant was literally loaded with seed pods. The bees had pollinated every flower.
The impact of this harvest was soon realized when I remembered that 'Chelsea Reach' was a petaloid, that is, having an extra row of petals in place of stamens. There has to be a firm justification in sowing open pollinated seed since many plant breeders compare this method to buying a lottery ticket. Knowing the parentage of your hybrids is definitely an asset in describing the end result of your accomplishments. It does not seem valid that a plant breeder, being paid by government funds, would admit to sowing open pollinated seeds; however, in this case an exception was made.

In the last five years, over forty controlled crosses have been made with 'Chelsea Reach' using various known hybrids. It was surmised that the petaloid form would be a highly recessive trait. This factor seemed to be true in the case of the open pollinated seedlings since only one in thirty showed this characteristic. In the controlled crosses, the ratio was quite different. The first batch of flowering seedlings produced three petaloid forms from 18 plants. It was about this time that I was introduced to the accelerated method of growing rhododendrons perfected by Weldon Delp of Harrisville, PA (see ARS Journal Vol. 39:2, spring '85).
Time of sowing the seed was the only major change that was made. Whereas Weldon Delp sows seed about mid December, I chose to sow October 1st, primarily so I could justify my allotment of greenhouse space at the institute. The results were truly gratifying. By the following October over forty percent of the seedlings had set buds in 12 months, and bloomed the following spring.

From approximately 100 seedlings that bloomed, more than thirty percent were petaloid. There were also some outstanding flowers of regular form. I believe the accompanying pictures prove the results. If time permits, the best of these petaloids will be crossed with flowers of similar color. It is expected that several of these petaloids will be registered in 1986 after another season of evaluation. Seeds from crosses made with 'Chelsea Reach' have been contributed to the ARS seed exchange, so act accordingly if you are interested.

Several hybridizers and growers in New Zealand, the United States and Canada have shown a keen interest in this line of breeding. These crosses have also shown a strong resistance to mildew and several have attractive fall foliage.