Monday, April 6, 2009

Hybridizing Peonies

The First Step
New cultivars of garden peonies are grown from seeds. At the turn of the twentieth century the procedure was to collect all the seeds you could find in your field, perhaps with preference given to seeds produced on favoured cultivars, and plant them directly into the ground. Some of these growers would plant a bushel of seeds each year, and that’s a lot of seedlings. This method of developing new cultivars worked sufficiently well then because in North America there were relatively few peonies considered exceptional. There was lots of room for improvement and planting a bushel of seeds offered a reasonable chance of coming up with something worthwhile and different. Integral to this method was the need for considerable arable land to grow thousands of seedlings. Times have changed.
Today, and over the last fifty years or more, the majority of the work at improving the peony has been done by relatively small nurseries and by interested backyard gardeners. In reality, the most significant improvements in the peony have always been made by enthusiasts working in their spare time primarily out of interest. Regardless , today if you are to accomplish anything worthwhile, you will have to give a bit more thought  to end goals and how they might be achieved. In a backyard garden you do not have the room to plant thousands of seedlings and raise them to blooming size. Fewer seeds of higher potential should be the basic tenet of the back yard peony breeder, and that takes a little planning.
An important part of planning will be selection of parents. This is not to say that you don’t already have peonies in your garden that would be useful in a breeding program, but only that a plan or two (or four) will help focus your efforts. Having knowledge of what has been done with certain peonies in raising new cultivars, or the pedigrees of the peonies you have in your garden, would be a great help in formulating a plan built around peonies you might already have, or as a tool in selecting new cultivars to be introduced into your garden.
Parentage information is available, but you have to hunt for it in resources that are not often readily obtainable, or are organized in a manner to make searching an exercise in tedium and frustration. Peony registration documentation, as published since 1923 by the American Peony Society in their quarterly Bulletin, yields the bulk of the information to be found. The work of Professor A. P. Saunders is fairly well covered in The Peonies, (1962), edited by John C. Wister, in the chapter written by Silvia Saunders. Nursery catalogues often give parentage information in the descriptions, and then there are scattered references in articles published in the APS Bulletin over the years. It is not all easy to find, and some sources contradict each other, so a reasonable amount of judgement must sometimes be exercised when evaluating the information given.
A recent search for peony pedigrees has turned up over 800 records and this information is published below. Each record is referenced to a source document. Research too needs a pedigree. There are columns for the pod parent, and for the pollen parent. The convention for many years has been to list the pod (seed, female) parent first in the generally used written format “pod parent x pollen parent.” The assumption has been made that this was always the case, but there are many instances where different sources have them reversed  for the same cultivar. The published “registration” information was taken as correct in these cases, unless other reliable sources supported changing them. The surest way to impart this information would have been to state which is pod and which is pollen parent, but few did it this way.
In some cases species peonies were listed as one of the parents. In the case of the officinalis peonies there were in cultivation several named selections, and these are specified in some listings. However, where officinalis on its own is given, one can’t assume that it was a wild species rather than one of the cultivated selections. As an example, Saunders very early on raised a chance seedling of some officinalis cultivar, pedigree unknown, which he used in some of his hybridizing work. Where known, this is specified, but in most cases the available information just doesn’t support saying anything more than “officinalis.”
In all cases where “Lactiflora” was given as a parent, it was one of the cultivated varieties. Where the lactiflora parent was specified, the cultivar name is used, otherwise it is listed as “Lactiflora cvr.” to signify a cultivar rather than the species.  In no instance was there any indication that a species lactiflora was used, and to do so would have been to lose the benefit of hundreds of years of breeding effort that the Lactiflora Group make available to us.
Where the term “unknown” is used, it almost always means that pollination was left to natural vectors. In those cases where the pod parent has its own viable pollen, this is likely to have been self pollination. Where the term “self” is used, this means that the hybridizer manually pollinated the flower with pollen of the same cultivar, or at least this was suggested from the information provided. Whether the pollen came from the same flower, a different flower on the same plant, or from a different plant of the same cultivar, all result in the bloom being considered self pollinated.
The list is incomplete. There are other available sources which have not yet been tabulated and periodic updates, including corrections, will be made to the list. Nevertheless, the more than 800 peonies already listed will give the potential hybridizer plenty of food for thought.

PDF version 
 .csv file for use with local spreadsheet or database