When I made the decision to begin hybridizing hostas, several factors entered into my decision. Was there significant room for improvement in the genus Hosta? Was there a shortage of hybridizing within Hosta growers, and would these new Hosta be marketable.
It became obvious quickly that there was room in the genus for improvement. Of course, there are limit as to how many large blue or green sieboldiana types that any garden would want, but there must be more. Very little work was being done with the narrow leaf and small species, while Hosta sieboldiana was being hybridized to death.
I propose to all hybridizers, a 10 foot rule. If you can not recognize a new Hosta from ten feet away, by name, that Hosta should not be saved. We need to work to introduce distinctive Hostas with good substance that actually grow.
With most of the new introductions coming from tissue culture, there is no new introduction of new genes. Nothing is changed genetically about the plant except the color of the leaves. There was also virtually no work being done in breeding for better flowers. The only way to improve flowers and include better genes was through controlled hybridizing.
Did I mention a shortage of hybridizers. What was initially viewed as a glut, was merely a lot of busy bees. While the bees have made a lot of folks a lot of money, how many bees spend the night contemplating the next days crosses? Bee crosses are great, but certainly lower the odds of producing better Hostas and certainly complicate the tracing of the Hosta family tree.
Would the new Hostas be marketable is another question. With the emphasis still on large sieboldiana types, the risk of using these different species is sort of like launching out in a boat, knowing the world is flat...it's a risky proposition, but someone has to do it.
Our serious breeding work has gone on for the last three years, during which time, over 200 crosses per year have yielded many many seedlings to evaluate. With the now common accelerated growth, seedlings can be flowered in gallon pots within seven months, making quick work of seedling evaluations.
Our schedule is as follows:
November 1 - end planting of seed
December 1 - begin transplanting into cell flats, reducing of seedlings from 20,000 to 1,000
May 1 - transfer seedlings into gallon pots, reducing of seedlings to 400, assign numbers to plants
July 1 - begin transplanting into garden beds
A large part of breeding with species is getting the plants to flower out of sequence. This can be accomplished in a number of ways, forcing the late flowering species to flower earlier, and forcing the early blooming Hostas to flower later.
Most of our work revolves around forcing the early blooming Hostas to bloom later, which is more easily accomplished than the reverse. Basically, any shock technique works well to force the hosta to re-flower. Since we do all of our crossing with containerized hostas, our possibilities are expanded tremendously.
One possibility is to keep the Hostas in a refrigerator until far past the normal spring emergence. If you leave the hosta in the refrigerator one month past the normal emergence time, then flowering will also be delayed one month.
Other easier and less prone to creating domestic disturbance techniques are by dividing the hosta, and by the heavy use of fertilizer and water. Growing Hostas in high areas of high sun (50% shade cloth in nurseries) works wonders in producing late or more exactly repeat flowering. I have had sieboldianas, undulatas, and virtually everything else reblooming in late summer and early fall. The only time that I have succeeded in setting seed on H. Undulata' was in September.
One of the species with the most promise is Hosta ‘Tardiflora'. With the late flowering and the shiny leaves, most any cross with H. ‘Tardiflora' is liable to yield some great results. We have a number of streaked and edged H. ‘Tardiflora' seedlings which are currently under evaluation.
Hosta tsushimensis is another hosta with which we have worked. Hosta tsushimensis has a very dominant gene for leaf shape and color (green) which is probably going to take several generations to change, but the incredible flowering of this species is worth the work.
Hosta ‘Hirao Tet', a supposed tetraploid dwarf that blooms in late summer is another winner. While only a few other species will set seed on H. ‘Hirao Tet', the pollen is quite fertile. If you need to dwarf any other hosta, flowers included, use H. ‘Hirao Tet' as a pollen parent.
Hosta venusta, one of our most common Hostas has been virtually neglected in breeding work. Most open pollinated H. venusta seedlings look remarkable like H. venusta. One of our very exciting crosses was a simple one with H. venusta and H. ‘Tardiflora'. There will be selections from this cross that should have rock gardeners jumping for joy.
One of my favorite Hostas is H. ‘Green Fountain'. Granted, the flower scapes could be a little straighter, but that's no problem. With H. ‘Iron Gate Supreme' as the pod parent, we not only shortened the blooms scapes, but made the flower larger and the plant more refined. As with all wishful crosses, there was no fragrance or variegation...perhaps in the next generation.
One of the most beautiful Hostas in existence is H. ‘Hirao 59', a kikutii selection. Both the foliage, shape, and flowers are outstanding (green). Why do we not have this plant in blue, with a white edge, or perhaps white flowers?
Another great plant that has just burst onto the scene in recent years is Hosta yingeri. With great substance, shiny leaves, and dynamite flowers, the possibilities are unlimited. I can tell from first hand experience that the mix of a blue sieboldiana and H. yingeri is striking! Now, if only some of my streaked H. yingeri seedlings will settle down.
The possibilities for hosta breeding, once the gene pool is expanded is tremendous. The diversity of foliage, shape, and flowers has only just been tapped. Within the next few years, many of the new breed of hybridizers will be dazzling you with some of the great new Hostas of the nineties.