by Bob Pries
Botanical names for hybrid irises are written Iris x species. They have more in common
with the TV program X-Files than just the X. The television series dealt with
FBI agent Molder investigating files that the department did not wish to touch,
because they contained paranormal phenomena that could destroy the reputations
of serious investigators. The botanical “X-files” have the same danger. In this
regard it probably puts my credibility at risk to discuss my collection of “X-files,” but here goes.
The Kew Checklist of Botanical Names lists almost 200 hybrid
binomials. For your consideration I have compiled a list, here, in the Iris Encyclopedia under “Botanical Nomenclature for Hybrids.” On inspection
there are several that are relegated to just a few synonyms and these have
interesting back stories.
Iris x violipurpurea and Iris x vinicolor
The first group I will mention brought about the fall of a
giant in botany at the time. John Kunkel Small was a celebrated botanist. He
had completed a flora of the Eastern United States and easily knew more about
its flora than anyone else. The herculean task he accomplished cannot be denied. But
he took a fateful train ride into the swamps of Louisiana. Looking out the
window he saw scores of irises like he had never seen. He came back and
collected a truckload that was sent back to the New York Botanical Garden to be
grown and studied. He and his colleague
Edward Johnston Alexander ultimately published a paper proclaiming about 110
species of irises in the Southern United States.
Iris brevicaulis, Iris giganticaerulea, and Iris fulva, the three parental species of Iris x volipurpurea
The botanical world was shocked! It was soon demonstrated by
Percy Viosca that most of these irises were not new species but hybrids of Iris
fulva, Iris giganticaerulea, and Iris brevicaulis. The Kew lists reflects this by changing 61 of these names to hybrid names rather than accepting them, except as synonyms of one master name for this parentage of
three parent species (Iris x violipurpurea). One other hybrid name was
accepted as the name for just Iris fulva and giganticaerulea crosses (Iris x vinicolor). So all of those names that
Small thought were different enough to be separate species, were essentially
lost. But this diversity could still be recognized as cultivar names.
Iris x volipurpurea "cultivars" 'Chrysophoenicia' and 'Chrysaeola' are similar to about 60 others that were originally considered species but were later classified as hybrids
Horticulturalists often complain about how botanical
names continually change. This is because they denote evolutionary
relationships. As the understanding of these relationships changes, so do the
names. Horticultural ‘cultivar’ names are meant only to distinguish the types
of plants and are usually unchanging. So these rejected species of Small became
cultivars such as ‘Aurilinea’, ‘Chrysophoenicia’ and ‘Rosipurpurea’ etc. and were
published as such in the 1939 American Iris Society Alphabetical Iris Check List. (The rule that cultivars could not have
Latin names came later.) These cultivar names
replace the botanical hybrid names.
Of course, when the world reacts it often
overreacts. Viosca admitted that he was only referring to the irises that Small
named in Louisiana. But many botanists immediately assumed that the irises that
Small described from Florida were also hybrids. Dr. Phil Ogilvie championed
more investigation into these irises and pointed out that each seemed to be
relegated to its own river system in Florida. Henderson recognized Iris savannarum
from Florida in The Flora of North American and relegated those other species
as synonyms of savannarum. Today some botanists take an extreme view that all these irises are examples of the same species using the name
Iris hexagona. So the pendulum swings.
Even botanists using some modern techniques claim Iris
nelsoni as nothing but a hybrid Iris x nelsoni. But this stance puts a very
rare group of irises from around the Abbeville, Louisiana area at greater risk because
how much support can you gather to protect a hybrid versus a species? No one
contests that in the past it developed as a hybrid from Iris fulva; but its
ecological requirements today are very different, and it certainly plays a
different role in the ecosystem. Other species have been shown to have been
developed through hybridization, such as Iris versicolor from Iris setosa and Iris
virginica.
Iris pallida and Iris variegata the two species that were parents of diploid tall-bearded "species"
Iris x amoena and Iris x squalens two irises resulting from the above cross
Another big group of botanical hybrid names (55) are those
relegated to synonymy with Iris x germanica. Sir Michael Foster convincingly
showed that a number of diploid tall bearded iris that had previously been
called species probably formed as the result of the two diploid species Iris
pallida and Iris variegata. The Kew Checklist gives Iris x germanica as the
hybrid name for this parentage. When one sees Iris x squalens, Iris x amoena,
Iris x neglecta, etc. This seems perfectly reasonable. But there are two other
groups that do not fit well in this hypothesis.
“Grandma's Old Blue Iris” a sterile triploid
First is the iris that is widely grown and called Iris
germanica. Unfortunately it has no other name to distinguish it except
“Grandmas Old Blue Iris” It is often referred to as triploid, and seems totally
sterile. Unlike the other “Germanicas” it is an intermediate iris. It is said
to have 44 chromosomes. Pallida and Variegata have 24 chromosomes. Many believe
it is the product of a 40-chromosome parent (20 chromosome gamete) and a 24-chromosome parent with an unreduced gamete. Iris albicans and Iris florentina
share a similar type of background, and are sterile; but presumably come each from
a different 40-chromosome parent.
The other group being referred to Iris x germanica are
presumably 48-chromosome tall bearded irises. Murray was troubled by the fact
that modern tall bearded irises were tetraploid while the earlier TBs were
diploid so he proposed a new name Iris x altobarbata, which in Latin means
tall-bearded. The Kew Checklist does not accept this name probably on a
procedural technicality. Another attempt to name the tetraploid “germanicas”
was made by Henderson with his Iris x conglomerata (a name not mentioned in the
Kew list. Henderson’s argument was that many species have gone into the TBs
including Iris pumila, hence the conglomerate. This name did not follow all the
rules of publication.
'Amas', a tetraploid I. germanica Despite two attempts, no satisfactory name has
emerged for this group. I have yet to
see strong evidence that the tetraploids emerged from the combination of Iris pallida and
Iris variegata which is how I. x germanica is being defined. There have been
several “species” that have been defined as I. germanica. One of the
key iris to be added to the pallida/variegata mix that precipitated tetraploid
offspring was ‘Amas’ which is probably best viewed as a cultivar. Itself of
hybrid origin it did not produce pods but its pollen changed the face of
tall-bearded irises by fathering the new tetraploid I. germanica cultivars.
There are a number of irises that were essentially cultivars,
and expressed here as botanical hybrids but could be candidates for the name of
the 48-chromosome species that are relegated to
Iris x
germanica if one does
not buy into the parentage as resulting from the two diploids
I. pallida and
I. variegata.
Like the X-files of TV, the data can be debated. I have just
pointed out two botanical hybrid names (
Iris x
germanica and
Iris x
violipurpurea)
that account for half of the list of 200. There are still many x-names that function
admirably to identify groups that originate from a given set of species. And there are also many more that have not
been included in the list. But perusing what is listed may widen ones knowledge
of various lineages. As agent Molder would say “The truth is out there.” Take a look at the X-Files,
here.
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