Hibiscus... Without a Net!Welcome to Hibiscus...Without a Net! Once again, my name is Sam Andrews writing this special column for American Hibiscus Society Members.
A Bit of Background
Recently, I enjoyed a very interesting conversation with Dr. Sam McFadden, a retired professor at the University of Florida- Gainesville, who spent much of his career focused on plant breeding. During that time, he specialized in hybridizing hibiscus, crape myrtles and roses. One of his hibiscus creations while at the University of Florida is 'Flare'. This cultivar, mentioned recently in the press, is a descendent of Hibiscus moscheutos ("mallows") hybrids. 'Flare' is a heavy blooming fuchsia single on a 4 foot x 4 foot plant. The Texas Extension Service has designated it a Texas Superstar. It only propagates through cuttings, not seed, and is available in garden centers.
Dr. McFadden has American Hibiscus Society associations that date back to his professor days that ended in the early 1980's. Now retired to a small town near Memphis, he continues tohybridize the Hibiscus genus in his spare time. He is an old friend and mentor of a next generation horticultural professor, Dr. Jerry Parsons at Texas A&M, who helped Sam McFadden and I meet.
It's All Relative
Living in West Tennessee, Dr. McFadden has been exploring crosses of herbaceous Hibiscus species. His goal is to create new inter-species cultivars that are hardy in colder climates. The focus of this work is to explore multi-generational crosses of Hibiscus rosa-sinensis, Hibiscus paramutabilis, Hibiscus sinosyriacus and Hibiscus syriacus. Specifically, he is using H. paramutabilis (or H. sinosyriacus) as cross-compatible foundations for bridging the genetic gap between the tropical H. rosa-sinensis and the temperate H. syriacus.
What are these species in the Hibiscus genus? Hibiscus rosa-sinensis is the genetic mixture of several tropical and sub-tropical species that are the primary focus of the American Hibiscus Society. Their survival requires temperatures above 32 degrees Fahrenheit, slightly acidic soils, and typically tropical nutrients.
Hibiscus syriacus is a very hardy Hibiscus native to East Asia and the National Flower of Korea. Grown all over the world, it is commonly called Rose of Sharon, Althea, or Syrian Rose. It grows in cold climates down to USDA Zone 4-5. Little care is needed for this landscape shrub.
Hibiscus paramutabilis is found in south-central China and is a genetic cousin of H. syriacus. According to at least one source, Hibiscus sinosyriacus appears to be very genetically close to H. paramutabilis, but shows slightly more H. syriacus influence. Taxonomically, these two "species" are often combined under the H. sinosyriacus name. They share the hardiness of their close relation H. syriacus. Seed of both of these hibiscus are available to the public.
It Has All Been Done Before
In my twenty plus years with Hibiscus, I have often been told or read that Hibiscus rosa-sinensis can only be bred with about ten different genetically-related species from the Indian and Pacific ocean areas. The writings of Dr. George Fister, Dr. Donald Egolf, Ross Gast and Dr. Yoshishige Tachibana that the Society published in the 1980's have furthered this thesis.
However, an Indian nomenclature that I received from a Hibiscus breeder, P. Mukundan, indicates that H. syriacus was successfully bred with H. rosa-sinensis in the early twentieth century. There is also a report that early Society member and world traveler, Ross Gast released seedlings may have some of the hardier Hibiscus species in their background. It is a fact that his primary breeding goal was to introduce hardiness into H. rosa-sinensis. Other crosses have been rumored or claimed over the years with H. moscheutos, H. coccineus, H. syriacus ,etc. However, proof remains elusive.
The now deceased Dr. Egolf of the National Arboretum (and the Society) did many years of very sophisticated hybridizing with H. syriacus as well as H. rosa-sinensis. He produced the famous H. syriacus tetraploids. 'Minerva', 'Aphrodite', 'Diana' and 'Helene'. He also produced one important H. rosa-sinensis "own-root" cultivar, Vulcan. In his American Hibiscus Society monograph published in 1984, he states that no direct cross resulted from using H. rosa-sinensis as a mother. However, Dr. Egolf did not say what his results were when used as a father, nor if he had success interbreeding relatives.
Sam McFadden states flatly that these inter-species crosses can indeed be done using a rigorous, lengthy breeding program and advanced techniques. Working with the high polyploid cultivars of both Hibiscus genus species, repeated crosses are made over numerous generations with each cross resulting in "some" genetic exchange. Back-crosses are also used repeatedly to emphasize the desirable traits from each Hibiscus species. Continuing this process over a long time, a unique genetic structure evolves into a stable new cross-species hybrid. Dr. McFadden say H. syriacus will set seed for him when H. rosa-sinensis is the father.Dr. McFadden told me that Dr. Ralph Dickey, a fellow professor at the University of Florida, had indicated to him that there were two extant combinations that had brought lavender/purple coloring into the H. rosa-sinensis gene pool.The two garden varieties that have been around since the first half of the twentieth century, are Dolores del Rio (or Dolores) and Myrna Loy. The American Hibiscus Society Nomenclature indicates that founder, Norman Reasoner, was the hybridizer using a mysterious cultivar named 'Hale Blue' as mother.
'Hale Blue' appears two other times in the Nomenclature. One has a Reasoner back cross to 'Myrna Loy' named 'Mahogany'. The other was a Bob Bowman cross of 'Hale Blue' times 'Lavender Dust' to produce 'Lavender Sky'.
Both Dolores del Rio' and 'Myrna Loy' are still grown around the world. Another Society founder and McFadden acquaintance, Eric Golby, wrote a 1975 Seed Pod article about these two miniatures titled "One Of Florida's First 'Blue' Hibiscus'.Dr. McFadden says that the breeding objective resulting in 'Myrna Loy' and 'Dolores del Rio' was to bring the blue/purple coloring found in some althea cultivars into the Hibiscus rosa-sinensis gene pool. It was not pursued in Florida because the color appeared "muddy".
From my own hybridizing efforts with "blues", I have noticed that the progeny tend to have very upward-growing plants with small leaves and smooth, gray bark. Upon reflection, these habits are indeed somewhat reminiscent of althea or Rose of Sharon.
By the way, Dr. McFadden thinks that Dr. Donald Egolf created 'Myrna Loy' and Dolores del Rio', despite the ASHS Nomenclature entry. He further believes that Egolf's sterile H. syriacus creation, 'Diana' may have H rosa-sinensis in its background. He recommended consulting some of the older Seed Pods which may have more information on this subject (as the 1975 issue indeed does).
A Matter of Good Breeding
For his own breeding program in Tennessee, McFadden is using a similar species to Hibiscus syriacus called Hibiscus paramutabilis. As previously mentioned, this species is often taxonomically lumped with an even closer relation name H. sinosyriacus.
The H. paramutabilis is the basis for crosses with both H. rosa-sinensis and H. syriacus as Dr. McFadden works toward genetically compatible hybrids. The H. paramutabilis is thus a bridge that he is exploiting to merge the two important horticultural species into hybrids possessing the best traits of both.
The H. rosa-sinensis crosses, he finds, produce the waxy leaves and yellow flower pigments of the father. The deciduous quality of H. paramutabilis remains a dominant trait, although leaf drop varies widely among his seedlings. In addition, the hybrid seedlings produce enlarged blooms and free-flowering qualities.
So far, the prize from his work is a H. rosa-sinensis hybrid, 'White Angel' (H. rosa-sinensis x H. syriacus 'Diane'), that will soon appear on the commercial market. 'White Angel' is a pure white that blooms heavily. Two other McFadden creations are 'Blue Angel' – lavender with a smaller flower and bush than 'White Angel' and 'Color Magic'. They will also be available for purchase soon.By the way, hybridizers, Dr. McFadden feels that a genetically sterile hybrid is more desirable since they do not waste energy and nutrients on post-flower reproduction. His reasoning makes sense even though most of us less scientific hybridizers will not really know if a seedling is sterile or not. What a wonderful conversation I had with Sam McFadden. He is a gentleman, and was an awesome fount of knowledge to this Hibiscus hobbyist.