Controlled Pollination
Basil C. Potter, Port Ewen, New York
The need to protect the integrity of a cross between two rhododendrons is not new, nor are the methods. In the wild nature protected the species with isolation and genetic barriers.
When we bring species together in civilization we confound nature's natural involvement, and have to provide artificial protection to prevent contamination of the species' natural purity, also to assure accurate percentage in a hybrid cross.
There are several methods we can use to protect a properly completed cross, one of which is the aluminum foil tube, which supersedes the white glassine paper bag and cotton method because it is safer, faster, neater and does the job better.
It has been used more than a decade and it is yet to be faulted. The tube solves the condensation problem, takes full advantage of available heat, is easy to make, quicker to use and provides complete protection. The tube is simple to make. Just cut a supply of 2" by 3" strips from a roll of aluminum foil. Then, when a pollination is completed, all one has to do is take one of the foil strips and roll it lengthwise on a short round pencil, next slide the tube partly off the pencil and crimp the end with the thumb and forefinger. Then slide the tube off the pencil and carefully place it over the pistil to a point just above the ovary; next gently pinch the tube on each side at the base to form a snug fit around the style.
The pollination is now safely protected from natural pollinators, wind, rain, etc. Very often when a flower is prepared for pollination the stigma is not receptive, a practical procedure is to coat the stigma anyway, and if the foil tube is carefully placed, the pollen will be there when the stigma becomes receptive.
When to remove the foil protection depends on the ensuing weather. If it is warm and sunny for three or four days after a receptive pollination, and by receptive it is meant if the stigma starts to swell or enlarge shortly after the pollen has been applied, it is a good sign the pollen is germinating on the stigma and starting to grow down the style to the ovary, where fertilization takes place.
If such is the case the foil protection could be removed within a week, if the stigma has dried. In the case of the non-receptive stigma you coated with pollen, it is best to remove the protective tube after several days and examine carefully. If the stigma indicates it has ripened, recoat with pollen. If not, try again next year.
Usually the second or third try meets with rewarding success, for few hybrids are permanently sterile.
For the practical breeder, controlled pollination saves time, space and wasted effort. Crossing hybrids of unknown parentage is not unlike searching for a needle in a hay stack, whereas a working knowledge of the laws of inheritance, homozygous species and controlled pollination together make it possible to create elepidote hybrids that are new, beautiful in flower, ornamental thereafter and just as climate hardy as you want them to be. You can create any pure color within the genetic potential of temperate zone rhododendrons. These laws greatly enhance one's ability to create new elepidote, pygmy dwarfs, dwarfs, semi-dwarfs as easily as larger ones.
Investigation and experimentation have placed these statements on very firm ground.