"Good News - Bad News" Some Observations of R. aureum hybrids
Dennis MacMullan, Kings Park, N.Y.
Basil Potter is the acknowledged Dean of R. aureum hybridizers - having appropriately named two of his numerous crosses - 'Miniwhite' (R. maximum x R. aureum) and 'Serendipity' (R. yakushimanum x R. aureum). His test grounds in Port Ewen, New York offer extremes in climate that add great value to his creations for almost all enthusiasts
I discovered some years ago that while R. aureum in its natural habitant can - and does withstand temperatures as low as -35°, that it cannot tolerate the heat of Eastern summers. A fully mature plant of R. aureum that was a gift from Basil in the Spring did not last until September due primarily to ¾ sun and resultant heat. A smaller plant (4 years old) was obtained in the Fall, put in a position where it received 3 hours of sun from 10 a.m. until 1 p.m. and allowed to develop. This plant wintered well - and died the following October. I talked with others who experienced similar failures with R. aureum and came to the conclusion that since even the best R. aureum are only a pale yellow, further efforts were not warranted.
Now for the "good news!" Both 'Miniwhite' and 'Serendipity' not only can stand ¾ sun, they seem to thrive on it. They bud well - and young. I decided to develop a few R. aureum hybrids of my own.
I repeated the R. yakushimanum x R. aureum cross. I crossed 'Wizard' AE, with R. aureum; Holy Moses x R. chlorops; 'Lackamus Cream' x R. aureum). I tried Jack Rosenthal's cross of ('INCA Gold' x R. yakushimanum, FCC) x R. aureum and others.
What I have found is that all of these plants react in the same manner if given ¾ sun. They bud early, are winter-hearty, develop sturdy root systems, and withstand heat...and they develop more intense color than R. aureum itself, while retaining its dwarf habit.
They require good drainage, and a fair amount of water in the summer to thrive. But since they are all very dwarf, minimal effort is required to develop a marvelous group of hybrids that will fit into those "little niches" that we all have in our gardens.
How about establishing an annual R. aureum Hybrid of the Year Award? How many more 5 and 6 foot yellows that don't quite look as good as 'Crest' do we need?