JARS v40n1 - A Hybridizer's Guide

A Hybridizer's Guide
Walt Elliott, Shelton, Washington

Hybridizing is an exciting and rewarding part of the rhododendron hobby. I'm sure those who hybridize, harvest and plant the resulting seeds will live longer just in expectation. My seeds! What will they produce?

Hybridizing began in the 1800's. A good portion of the interest centered in the British Isles. Plant and seed gathering expeditions from England made trips to China and Nepal. The discovery of new species and the growing of seeds gathered on these expeditions formed the base for hybridizing from which most of the present day named varieties have been produced.

What Is A Hybrid?
It is the progeny resulting from the cross breeding of two different species, a species and a hybrid, or the crossing of two hybrids.

The Hybridizing Process
Note: I usually cross pollinate at mid-morning on a warm day.
1.  When pollen is evident on the anthers, remove 3 or 4 stamens, then brush the pollen bearing anthers across the end of the pistil (the stigma). The stigma is sticky when receptive to pollen.
2.  Control pollination by removing the corolla or flower petals and the stamens from the flower being pollinated.
3.  Cover the pistil with aluminum foil for control against chance contamination from insects, wind, birds, etc. Foil also protects from weather and holds the pollen until the stigma is receptive.
4.  When one has had difficulty in getting seed production:
a.  Favorable conditions can be induced and controlled in the greenhouse.
b.  Bring in potted or freshly dug and balled rhodies for your experiment.
5.  When using different parents in a pollination, it is best to let the plant having the most desired qualities bear the seed.
6.  Keep records:
a.  Label the cross.
b.  List parents in your notebook.
c.  Mark the date of cross.
d.  Note the time of day cross was made.
7.  Prospective parents which bloom at different times can be crossed by collecting and storing pollen from the early bloomer in a gelatin capsule. Store in refrigerator until time of use.

Some Breeding Goals
Note: It takes as many years to grow an inferior plant from seed as it does the superior plant you hope to produce. With this in mind, select the best parent possible for your particular goal.
1.  Plant habit - most present day hybridizers are working toward medium compact or dwarf sturdy compact plants.
2.  Good leaves - size, color, shape.
3.  Hardiness - frost and heat resistant.
4.  Size of flower and truss.
5.  Fragrance - use R. fortunei , R. diaprepes , R. luteum (azalea).
6.  Lasting quality of the flower.
7.  Extend blooming season.

Problems To Eliminate
Note: Try to use parents which do not have these characteristics.
1.  New growth through and around flower.
3.  Sprawling characteristic.
4.  Poor leaf retention.
5.  Attraction to pests.

Breeding For Color And Size
1.  To produce a large flowering medium growing white try: 'Helene Schiffner' x 'Travis L.', R. yakushimanum x 'Mrs. A.T. de la Mare'.
2.  For yellow — in the mid-sixties a flavonol called gossypetin was found to produce yellow flowers. This is evident in the following:
a.  Species — R. wardii , R. campylocarpum .
b.  Hybrids — 'Crest', 'Hotei', 'Mrs. Lammot Copeland'.
3.  To introduce orange or intensify the yellow:
a.  Species — R. dichroanthum .
b.  Hybrids — 'Bergie', 'Whitney's Orange', 'Jasper'.
4.  For smaller plants:
a. R. yakushimanum as seed parent.
b.  Use pollen from 'Golden Witt', 'Moonstone', R. caloxanthum , R. dichroanthum .
The field of hybridizing is endless, consider using elepidotes, lepidotes and azaleas - evergreen and deciduous.

References
Leach, David, Rhododendrons of the World , New York, 1961, pp. 383-423.
Quarterly Journal ARS 31(1):38, 31(2):113, 31(3):138, 32(1):23, 32(4):213, 33(2):78, 33(3):176, 33(4):214, 34(2):92, 37(4):104.