JARS v51n2 - A Search for the Red and White Bicolored Rhododendron

A Search for the Red and White Bicolored Rhododendron
Chris Trautmann
Amelia, Ohio

For over a decade I have been working to create a red and white bicolor rhododendron. The plant that most nearly reaches this goal is a hybrid I have named 'Rhodstar'. 'Rhodstar' is the result of a cross I made in the mid 1980s ('Java' x 'Swen'). The primary goal of this well-thought-out cross was to obtain a true red/white bicolor that is adaptable and hardy.

Although other bicolors existed, they fell short of my ideal. 'Madame Wagner' and 'Lady Armstrong' were weak in color contrast, and 'Consolini's' Windmill' lacked hardiness and is only now becoming available. Other notable candidates were 'Amphion' and 'Sandwich Appleblossom' which are excellent bicolors but stay in the pink/white realm.
Other notables that failed the "emotion" test were 'Wendy Lyn' (hybridized by Dr. Robert Moyers, grown by Weldon Delp) and Hans Hachmann's 'Ann Lindsay'. 'Wendy Lyn' is exactly what I wanted to attain but completely lacked hardiness and adaptability. The Hachmann beauty 'Ann Lindsay' is barely H-2 in hardiness but would be my choice in USDA Zone 6 and 7. And lastly, 'Fantastica', considered a fine bicolor, does not darken up enough in the United States but becomes emphatically a red/white bicolor in Northern Germany.
To obtain the bicolor effect that I so desired, I had to select the proper "fader" or "dilution factor" parent. As part of the process, my selection was 'Swen'. 'Swen' is a cross of R. yakushimanum and 'Mars' by Willard Swenson of Eugene, Ore. The compact "yak" hybrid has nice large trusses of white with a pinkish red edge.
Most hybridizers have experienced the fading with most R. yakushimanum crosses that we have made. The dilution efficacy is most prevalent in a "yak" crossed with a darker color. In other words, by crossing 'The Hon. Jean Marie de Montague' with R. yakushimanum you will never get a compact growing Jean Marie with Jean Marie flowers! But if you take a dark red that has some white in the deepest part of the throat, you can obtain this effect.
Examples and proof are: David Leach's very hardy 'Java' ['Mars' x ('Mars' x R. catawbiense , red-flowered)] crossed with 'Swen'. The seedlings of this cross started to flower in 1988-1989, and after bringing 17 seedlings to flower, I picked the best one. Many of the siblings had good bicolor flowers, but #6 was the best. It has been named 'Rhodstar' and will soon be available. It is plant hardy to -25°F and bud hardy to -15°F with a compact plant habit.
Other seedlings for bicolors I am growing are the following crosses: ('Java' x 'Fantastica'), ('Rhodstar' x 'Sandy Petruso'), ['Rhodstar' x ('Maxine Childers' x 'Anna Delp')].

Chris Trautmann, a member of the Great Lakes Chapter, owns Mowbray Gardens in Amelia, Ohio, and breeds and propagates rhododendrons, dwarf conifers and American hollies.