JARS v50n2 - Hand Pollinated Seeds Only?

Hand Pollinated Seeds Only?
George Ring
Bent Mountain, Virginia

Being a regular contributor and recipient of seeds from the ARS Seed Exchange, the announcement in the Summer 1995 Journal caught me, and perhaps others, by surprise, i.e., "we are no longer going to accept open-pollinated seed - except in cases where a species is known not to hybridize or the species is very rare." My first reaction was one of disappointment. However, the longer I thought about it, the more logical the announcement seemed to be. Several letters from George Woodard, chairman of the Seed Exchange, helped to explain the change in policy. The main reason for the change is that there are few requests for open-pollinated seeds. Most members who grow rhododendrons from seeds want to start with hand-pollinated seeds, and well they should, since the character of the resulting plants is much more predictable and future hybridizing can be better planned when the genetic background of the parents is known. In addition, just receiving and listing hundreds of open-pollinated seed lots requires a tremendous effort resulting in very little benefit to either the members or the Seed Exchange.

In the early history of the ARS, few members had species plants but wished to add species types to their gardens. In an effort to provide access to more plant material, beginning in 1965 the Seed Exchange accepted and distributed open-pollinated seeds of species rhododendrons. This practice of distributing open-pollinated seeds of species has continued through 1995, although more and more contributors have provided hand-pollinated seeds of species as well. Except for a few early listings, accepting and distributing open-pollinated seeds of hybrids is a more recent development. A sample of seed lots available by category is given in Table 1.

As the table shows, there has been a gradual increase in the number of hand-pollinated seed lots, but there has also been a large number of open-pollinated seeds as well, with a significant recent increase in open-pollinated seeds in the hybrids group.

Distributing open-pollinated seeds in the past when plant material was less available has benefited many members by making it possible for them to greatly increase the diversity of rhododendrons and azaleas in their gardens, including seedlings of species which have beautiful flowers and foliage, some of which closely resemble authentic forms. But now seems an appropriate time for the Seed Exchange to cease accepting and distributing open-pollinated seeds for a number of reasons. First, many more members who contribute to the Seed Exchange have authentic species that can be self-pollinated or crossed with other forms of the same species. Second, much more is known about making controlled crosses (hand-pollinations), and this information is known by many more members. Third, members who request seeds from the Seed Exchange want hand-pollinated seeds, and very importantly, growing species from hand-pollinated seed will help to reduce the confusion which abounds about which plants in our members' gardens represent a "true" species. This confusion is not new. Many years ago members found that even species plants imported from some of the best nurseries in England did not always conform to published descriptions for that species, and so-called "species" varied greatly from one member's garden to another. To try to bring an end to this problem, a small group of dedicated members started meeting over 30 years ago. Eventually they decided that the establishment of a rhododendron garden containing only true forms of species might be a reasonable solution. Their subsequent success in starting such a garden is documented in History of the Rhododendron Species Foundation written by Clarence Barrett and published in 1994. In this book the development of the garden is well chronicled as are the characters of those people who made it possible.

It should be recognized that George Woodard's request for hand-pollinated seeds of species rhododendrons is really a request for seeds from authentic forms of the species. Hand-pollinated flowers on plants grown from previously distributed open-pollinated seed should not be expected to reproduce a true species even though the seed parent may somewhat resemble a species. If there is any doubt about a plant being a true form of a species, the owner may want to grow a population of seedlings from hand-pollinated seeds of the plant and check for significant variation in the seedlings. If there is such variation the owner should refer to the parent plant as "a seedling of 'x' species." Questionable plants may also be "keyed" to published descriptions.

I strongly support the new policy of the Seed Exchange to accept and distribute only hand-pollinated seeds. Participating members have demonstrated that they can and will contribute hand-pollinated seeds. This practice will raise the quality of seeds and make the Seed Exchange more useful to all. Below is a brief description for hand-pollinating rhododendrons and azaleas.

A Method for Hand-Pollinating Rhododendrons and Azaleas
Hand-pollinated flowers of rhododendrons and azaleas is a way of achieving predictable results when growing seeds of species and hybrids. Hand-pollination also makes your seeds acceptable for distribution by the ARS Seed Exchange. Participation in the Seed Exchange makes it possible for members to share hybridizing ideas and/or seeds of authentic forms of species. The hand-pollination procedure is easy and, when the parents are compatible, is usually successful when a few important steps are taken, as follows:

A.  Just before the flower intended to be the female parent opens, remove the flower petals and the stamens. This helps to prevent contamination by unwanted pollen. It may be helpful to completely remove adjacent flowers as well.

B.  When the tip of the stigma remaining becomes sticky (this may take a few days), touch it with the stamen of a flower from the male parent. Pollen from the stamen will adhere to the stigma. You have now done all that is necessary for the plant to produce hand-pollinated seeds. Tag the pollinated flower with the name of the female parent and the male parent, in that order. Seed pods that form during the summer may be collected just before the first frost.

Note 1. Pollination is usually most successful on warm days. If it looks like rain soon after pollination, the pollinated flower can be temporarily covered with a plastic "baggie."

Note 2. If the male parent blooms earlier than the female, the pollen from the male plant can be collected and stored until the female plant is ready, as follows:

Collect anthers just before the male flower has opened. Pre-dry the anthers by placing them in a gelatin capsule which is tagged and placed in a refrigerator at about 50°F for a few days. When the anthers are thoroughly dried, the capsule can be placed in a jar along with a desiccant separated from the capsule by a layer of cotton, and the jar stored in a freezer. To prepare the pollen for use, remove the capsule from the jar and allow it to warm to room temperature. The pollen is then ready to be placed on the prepared flower (stigma)of the female plant. Unused pollen can be re-frozen. While frozen, it will remain viable for several years.

References
1.  American Rhododendron Society. Seed Exchange catalogs, 1967, 1977, 1987, 1995.

2.  Barrett, Clarence. A history of the Rhododendron Species Foundation. Eugene, OR: Positive Attitudes, Publisher: 1994.

3.  Galle, Fred. Azaleas. Chap. 12, Hybridizing azaleas. Portland, OR: Timber Press: 1985.

4.  Kehr, August. Breeding for a purpose. J. Amer. Rhod. Soc. 20:130-141; 1966.

5.  Leach, David. Rhododendrons of the world. Chap. XIII, Breeding rhododendrons. New York: Charles Scribner's Sons: 1961.

6.  Muller, Albert J. Tips for beginners: mechanics of basic hybridizing. J. Amer. Rhod. Soc. 50:36-37; 1996.

7.  Ring, George. Personal communication with George Woodard, chairman of the ARS Seed Exchange; 1995.

George Ring is a member of the Potomac Valley Chapter.