The Use of Frozen Pollen For Controlled Pollination
Jens Chr. Birck
Copenhagen S, Denmark
My approach of using surgical tape (micropore) for controlled pollination as described in ARS Bulletin 1979, page 20, and in P. A. Cox, "The Larger Species of Rhododendron," page 318, has been used by members of the Denmark Chapter for a period of 5 years with excellent results. The use of surgical tape has also proven very practical in the special case of pollinating with frozen pollen.
When using frozen pollen, it is very important to carry out the pollination in two stages to increase the probability of success, as it seems that frozen pollen has a very short period of viability when thawed.
The first thing to do is to seal the stigma of the flower to be pollinated with surgical tape just before the flower opens (this can be done by pressing the flower open with the fingers). When the stigmas of the other flowers in the truss are ready for pollination (when they become sticky), the tape is removed, the thawed pollen applied, and the stigma sealed again with new tape. The pollen is put back into the freezer and the pollination is repeated after 2 days.
Concerning the subsequent growing on of the seedlings, I have observed it to be very beneficial to rapid healthy growth under artificial light, to use an electrical fan in my basement growing room. The fan is used in connection with a timing device giving 1 minute on and 20 minutes off. The fan is placed 0.5 meter away from the plants, blowing horizontally.