JARS v51n3 - Tips for Beginners - Hybridizing Notes: About Your Parents

Tips for Beginners - Hybridizing Notes: About Your Parents
Jim Barlup
Bellevue, Washington

As hybridizers we have the unique opportunity to design new rhododendrons. Our success is dependent upon the selection of the seed parent and the pollen parent that we use for crossing. The hybrid parents pass their characteristics (such as plant habit, foliage, shape of truss, color, fragrance, bloom time, early budding, etc.) onto their offspring in a somewhat predictable fashion. (But be aware, there may be incredible surprises!) The challenge to the hybridizer is to find the parents that are capable of transferring the combination of desired traits to a new hybrid. I do not have a scientific background, so my approach has been through experimentation and the careful observation and recording of results. This process may not have been the most efficient, but it certainly has been exciting and rewarding.

Always start with specific goals in mind. This goal could be a semi-dwarf plant with the foliage and flower of Taurus' or a low compact plant with full deep purple trusses like 'Purple Splendour'. You may want to create a fragrant peach, a hardy golden yellow, a flower with picotee edges or a spectacular plant that buds young. Your choice of parents will determine how well you reach your goals. Skill in selecting parents comes from a variety of sources. I research sources about parentage and look for patterns that emerge. My own experimentation and that of other hybridizers show which characteristics are passed on to the offspring. Failures are as important as successes since they tell you which plants to eliminate from your program.

My hybridizing career started in 1975. At that time I had a definite goal in mind. There was a lack of apricot, orange and peach colors. I wondered why - could I create them? I collected just about every plant within that color range; among them were Dido Group, Medusa Group, 'Fabia' and every form of Rhododendron dichroanthum that I could find. This color range led me into many yellows that quickly became a dominant part of my hybridizing. In looking for a pale apricot, I crossed Dido Group ( R. dichroanthum x R. decorum ) with 'Hélène Schiffner' (a pure white unknown cross). From this cross I raised six plants with beautiful foliage, all with muddy purple flowers. The unknown in 'Hélène Schiffner' turned out to throw lavender flowers.

The oranges, apricots and peaches that I created were lost to harsh winters. However, after 22 years of hybridizing, they are still in my dreams. I actually created the orange I was seeking. It was a compact plant with buds opening deep red and turning to apricot-orange, big calyxes, ball trusses and dense dark green foliage with slight indumentum. The cross was ('Paprika Spiced' x 'Hill's Low Red'*). I lost every plant in the 1987 freeze. Perhaps they would have survived if they had not been transplanted only three weeks prior to the freeze. Subsequent crosses never came close to the original.

Through this experience, I found the key to orange rhododendrons, 'Hill's Low Red'.* It used to be called "Red Yak." It looks like a R. yakushimanum hybrid because of its heavy indumentum but it was deceiving. Rhododendron yakushimanum hybrids are hardy and fade to a bluish-red color. Hill's plant was not hardy (perhaps to 5°F) and the flowers faded to an orange-red. I therefore conclude that it is not a yak hybrid and may possibly be a R. haematodes hybrid. The big question is, what was the other parent? Crosses with Fantasy Group have produced golden yellows. Crosses with other yellows have produced orange-red flowers with red throats. Just this April my first ('Anita Dunstan' x 'Hill's Low Red'*) bloomed. It has a tight full truss, huge calyx and deep coral orange flowers with a red star center. After 22 years, I am still in pursuit of my initial goal of creating orange rhododendrons. The next step should be to cross 'Hill's Low Red'* on some of the hardiest yellows such as 'Capistrano' and 'Vinecrest'. Are there genes within these plants that will produce semi-hardy oranges? Only time will tell.

rhododendron drawing

The winter of 1987/'88 was one to remember! Temperatures ranged from zero to 10°F for about 10 days, very cold for the Pacific Northwest. In the fall of 1987 I potted about 40 varieties in 1,150 pots and placed them under the fir trees for protection as I had done for the previous nine years. In the spring I had lost the seedlings in 800 pots. It was interesting to see which crosses were undamaged such as ( R. yakushimanum x 'Mrs. J.G. Millais') and ( R. yakushimanum x R. macabeanum ). This was a definite surprise, perhaps because I was using the Exbury form of R. yakushimanum . Crosses made with 'Mrs. Furnival' survived as well as many of the 'Nancy Evans' crosses. The winter weather caused a lot of damage, but it was nature's way of weeding out the tender varieties. The survivors would become the nucleus for future parents.

Foliage is another worthy goal. Each fall as I plant the new seedlings and transplant the 3- and 4-year-old plants, I evaluate the plant habit and foliage of each plant. As the years pass, I can see a definite pattern as to which plants have a good plant habit and throw good foliage. I continue to use parentage that produced these plants in my hybridizing program. Rhododendron yakushimanum crosses will generally produce good foliage, even with as little as one-quarter R. yakushimanum parentage. 'Nancy Evans' is an excellent parent. It transmits beautiful foliage and excellent branching patterns.

Noting which plants set buds in the containers and at what age provides valuable information. 'Jessie's Song' ('Nancy Evans' x 'Golden Anniversary') and 'Fire Rim' ('Nancy Evans' x 'Pink Petticoats') budded in one-gallon containers (6-inch pots) as seedlings. Every year since they have set buds on every stem. This year I had about six seedlings of various crosses that set buds in one-gallon containers at the age of 2½ years. One of these plants is 'Silk Ribbon' ('Anita Dunstan' x 'One Thousand Butterflies'). These are traits worth pursuing.

One of my favorite plants for hybridizing is 'Mindy's Love' ('Nancy Evans' x 'Lionel's Triumph'). It is a strong growing, good foliage plant with a large full yellow truss. Its various offspring have consistently produced good foliage. The problem with 'Mindy's Love' is that it takes four to five years or more to set buds. Fortunately it appears that this characteristic doesn't carry over to the offspring. Cuttings of 'Wind River' {'Mindy's Love' x [('Whopper' x 'Lem's Cameo') x ('Whopper' x 'Tropicana')]} budded as a rooted cutting. A cross of 'Mindy's Love' and 'Jessie's Song' produced seedlings that set buds in 6-inch pots. 'Jessie's Song' had passed its heavy and early budding traits to its offspring.

My hybridizing program has elements of early and late blooming plants. I frequently use R. yakushimanum to downsize the large early bloomers. It worked well with R. macabeanum (a large early bloomer). The 10-year-old plants from this cross bloom in early April and vary in height from 20 inches to 3 feet. The goal was almost accomplished; however, the original plants and the cuttings are very slow to set buds. In spite of its slow budding, I will continue to use it with hybrids that bud young because of its beautiful foliage and flower. For a late bloomer, a cross of R. yakushimanum and 'Independence Day' seemed a logical choice. It produced a low grower, with the largest and fullest trusses of any of my yakushimanum crosses. It transmitted the bloom time of R. yakushimanum rather than the later bloom time of 'Independence Day'. Reversing the cross might give a later bloom time as the seed parent is usually dominant. The plants from each of these crosses are stepping stones to my ultimate goal. The market for late bloomers (June and July) might increase if we can provide low growing, compact plants with exciting colors. Combine this with sun tolerance and long lasting flowers for those hot summer days, and we'd have a winner. What a challenge!

Find the parents that give you what you envision. I made a cross using ('Fancy' and R. yakushimanum ), a low grower with a full white truss and a bit of a yellow eye as a seed parent. The pollen parent was 'Exbury Calstocker', a tree-type rhododendron with a large white truss with a red eye. I hoped to create a lower growing, spreading 'Exbury Calstocker'. I got a dense shiny dark green foliage plant with a smaller truss of pure white flowers (23 to a truss) with a red eye. The plant was 3 feet tall at 10 years. The plant name is registered as 'Snow Candle'. It is very close to what I had hoped to create.

Every spring you eagerly await each new bloom! Admittedly, there can be 3 to 10 years of anticipation and one day of disappointment. The thrill of five outstanding plants makes up for the disappointment of the 95 that just don't qualify. Five percent is a good average, enough to keep you excited about the coming year. Our goals change as we gain more knowledge. The need for certain types of plants beckons and we heed the call. The year 1995 started me on an odyssey with Eastern hybrids. As my knowledge grows, my choice of parents will improve.

Learning from our own experimentation is a slow process. It is extremely valuable for hybridizers to keep records, to share the knowledge they have gained, to hear other viewpoints, and to get inspiration from the work of others. Other sources of information can help improve our decisions in selecting parents. Books containing the history of parentage, ARS Journal articles on hybridizing and hardiness, proceedings of hybridizers' meetings and roundtable discussions all provide a wealth of information. Your choice of parents will determine your future in hybridizing.

How exciting it is to have my whole garden before me as an artist's canvas and my palette of pollen from the East and West!

* Name is not registered.

Jim Barlup is a member of the Cascade Chapter.