Peony taxonomy - boring.

Jim McKenney
Thu, 05 May 2011 08:42:21 PDT
Jim W. took the time to write a detailed piece on the taxonomy of peony groups. I wish more people with specialized knowledge would take the time to do this now and then.

I think there is a lot more to be said about what Jim W. wrote.

For instance, Jim W. wrote "There is no taxonomic level called a division."

That's not exactly true; I think what Jim W. meant is that there is no rank of formal botanical taxonomy called division. But formal botanical taxonomy is not the only source of our group names. In most groups of long cultivated garden plants (for instance, roses, daffodils, irises, lilies) hybridization has proceeded to the point where the relationships to the true, natural species is utterly obscured. In fact, one of the fascinating things for me about reading books about our garden plants progressively - i.e. in the chronological order in which they were published - is that such reading allows comparisons over the decades, sometimes over the centuries, of the various classification schemes which have been used.

Only last week did I finally realize the significance of the name "squalens" as applied to tall bearded irises. I had always known how to apply the word to irises - in other words what it meant on a practical level. But the deeper significance of the word only became apparent to me last week when I was reading two iris books, one from the 1960s and one from the 1930s.

Irises provide a good example of the way in which the early classifications were strongly influenced by the then current perceptions of botanical relationships. The Linnaean species are a mixture of true species (species in the modern sense) and others which are not species at all in the modern scientific sense - they are nominal species, The early hybrids were sometimes grouped according to their apparent relationship to the Linnaean species. This led to odd situations, for instance where there was a true species named Iris variegata and at the same time a group of hybrid irises for which a group name variegata was used.

As hybridization within a group moves into levels of greater complexity, the relationships of the hybrids to the ancestral species becomes obscured. At that point, various artificial classification schemes are developed to allow sensible classification of cultivars.

Here's the significance of this: for many plants two systems of classification exist simultaneously. One system is the natural system of formal botanical taxonomy whose most basic premise is that the members of a taxon are more closely related to one another than they are to the members of any other taxon of similar rank. The other is the artificial system of classification widely used in horticulture, where relationship is irrelevant or at any rate much secondary to completely artificial (rather than natural) criteria.

These systems of classification (natural and artificial) usually produce strikingly different results. For instance, in the natural system of classification, a given plant has only one position at a given rank. In artificial systems of classifications the various forms of one original seedling plant can appear simultaneously in multiple positions of the classification.

Here's where the word division comes in: in some important groups of cultivated plants such as lilies and daffodils the major groupings are called divisions. These divisions are very loosely based on ancestral species or groups of species. Often, the historical fact was that the members of one division did not hybridize easily or at all with members of other divisions. When hybrids between the members of the various divisions finally appeared, the resulting plants were called interdivisional hybrids.

Peonies are still in a relatively early phase of their hybridization. Even the amazing work of A.P. Saunders in the first half of the twentieth century (he made a effort to use every species of peony he could obtain in his hybridization work; some of his hybrids have four, maybe more, species in their background) has not changed the fact that the majority of peonies grown to this day (and the only ones people who do not attend peony shows are ever likely to see) are cultivars (not hybrids) of Paeonia lactiflora.

True hybrid peonies are finally becoming readily available, and among them are of course the Itoh hybrids. As commercial entities, these are relatively new (although somewhere around the house I still have the first commercial offering of the Itoh hybrids by Louis Smirnow about forty years ago - at that time no one including Smirnow himself seemed to know just what they were). No doubt there are those who feel a classification which looks back to the botanical classifications of botanists is still appropriate for these plants. But if the history of peony hybridization develops as the history of the hybridization of daffodils and lilies has, the time will come when the relevance of botanical referents will be irrelevant.

Jim McKenney


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