QBARS - v31n1 Hardiness in Rhododendrons is Simply a Matter of Breeding

Hardiness in Rhododendrons Is Simply A Matter of Breeding
Basil C. Potter, Port Ewen, New York

Proof of this statement was amply demonstrated for all to see by an Englishman a hundred years ago when he shipped large numbers of his newly created Iron Clads to the New York City area. Today these hybrids are gracing gardens in America from coast to coast.
Not only have they disallowed the myth regarding rhododendron hardiness, the Iron Clads have demonstrated an adaptability to an astonishing range of soils that vary considerably in their texture, productive capacity and soil reaction. We can only speculate on the parentage of the Iron Clads, for no records of crosses or pollinating methods were disclosed. Actually they are not all that important anyway, because the parentage of hybrids that were created without the benefit of controlled pollination are of little value to the serious breeder.
History tells us that R. catawbiense and R. maximum were among the first species brought into England, and we know that the blue shading so characteristic of R. catawbiense hybrids prevails throughout the Iron Clads.
We can be quite sure that the hardiness factor came from one or both of these species. It also indicates that pure color Asian species were contributors in the creation of the reds and pinks.
The purpose of this phase of discussion is to focus attention on the fact American breeders have the two hardiest elepidote species in the Genus Rhododendron. Both have the genetic ability, and do impart a high degree of hardiness to their offspring when crossed with tender Asian species, used to impart color or other desirable characteristics.
The northern R. maximum should not be confused with its southern form. The northern form is believed to be hardier, lower growing, highly adaptable, and its purity is without question.
The idea to investigate and seek understanding through experimentation with genetic hardiness started in 1952. Ten years later it became a full time hobby, and the quest for understanding continues.
Accumulated evidence thus far justifies the statement that you can successfully breed for hardiness in rhododendrons. You can breed hardy rhododendrons that are pure dark red, red, scarlet, pink, pale yellow and many mixes there from.
You can breed hardy elepidote rhododendrons in any size, from pygmy dwarfs, dwarfs, semi-dwarfs and larger if you wish. They can be free flowering with truss and flowers in keeping with plant size.
The flowers are of good texture and seem to have inherited the all-weather characteristic of the hardy parents.
Seedlings set flower buds while very young.
Cuttings root easily and flower soon thereafter.
Perhaps it should be said now that this work is being carried on in a mini nursery, and no plants are for sale. They are, however, available for viewing by those seriously interested in breeding for hardiness.
Breeding for insect and disease resistance is not an impossibility. In closing, may it be repeated. Hardiness in rhododendrons is simply a matter of breeding.