OSU plant breeding program shows progress on promising new cultivars

The plant breeding program at Oregon State University is continually working to bring new plants to market that will make growers more profitable and perform well for consumers.

On behalf of the program, I wanted to update the industry on these efforts. New plants build excitement for everyone, and I think we have a few that do just that.

The last year has been an exciting time and feels like an inflection point — though, maybe I have said that before. But that is the mantra of a plant breeder. We always believe there is a great plant in the next population or the next set of crosses will prove to be revelatory. In other words, hope springs eternal.

Below are a few of the projects and plants that I think are worthy of notice.

Hibiscus syriacus ‘Flamingo’ PPAF

It is approaching a decade that I have been working on altheas, also known as rose of Sharon or Hibiscus syriacus. In that time, I have heard from industry and consumers about what they are looking for.

Of course, more saturated colors are always in fashion — people want “true blue” and “really red” cultivars. We are always looking for better flower colors and many of our polyploid selections provide that depth of color.

But dark green foliage, especially early in the season, is equally important — perhaps more so. No one wants to pay top dollar for anemic-looking plants.

During the breeding process, we discarded thousands of plants with inferior foliage color and arrived at our first release, ‘Flamingo’.

‘Flamingo’ is a seedless, single pink cultivar with deep green foliage on a compact, but vigorous grower.

The cross for this selection was performed in 2013. We have been watching it since then and it has been a reliable performer. It is available for non-exclusive licensing from Oregon State University by contacting Denis Sather (Denis.D.Sather@OregonState.edu).

For more information, please visit https://Horticulture.OregonState.edu/File/Hibiscus-Syriacus-Flamingo.

Tree-form Hibiscus

In recent years at the Farwest Show, I have walked the show floor looking for comparators to plants I’m working on. What I saw in althea was most growers training them as standards. The resulting plants are lovely and fit the gardening need, but it seemed to me that we could achieve that in an easier way for growers than the effort to turn a shrub into a small tree.

To that end, we started using ‘Lohengrin’ and ‘Tosca’ in crosses with various althea cultivars. These two cultivars are hybrids of H. syriacus and H. paramutabilis that tend to be larger, more tree-like than althea. Our hybrids exhibited a wide range of growth habits, flower forms and seed production.

Most exciting to me, many of these plants naturally grow vigorously with a central leader to produce small trees. One grower noted that the least vigorous of these selections grew twice as fast as the industry standard. It will require far less effort to train altheas as trees than other cultivars. They have larger flowers and most are infertile — meaning fewer seedlings to control in production.

One question is their hardiness. That is being addressed by current testing in collaboration with the Morton Arboretum. Selections include singles and doubles in mostly white and lavender. The size of some of these flowers are truly noteworthy.

There’s more work to be done, but these hold the promise to be game changers. We made the original crosses back in 2015, with evaluation ongoing since then. I continue to be impressed with their vigor, novelty and beauty. These seem like an easy sell, but the proof is in the production and we have several growers testing them.

Butterfly bush

I have been working with the Oregon Department of Agriculture (ODA) on the issue of Buddleja and how to handle the flurry of new cultivars that have been introduced.

As most are aware, Buddleja was banned in Oregon and elsewhere due to its invasive nature. However, the ban was amended in 2009 to allow sterile, interspecific hybrids. Since then, ODA has approved 14 cultivars based on either 98% reduction in fertility, or because they were hybrids.

We have spent the last three years evaluating a suite of 34 cultivars. These include classic cultivars with high fertility, modern cultivars on the market that are reportedly sterile, and modern hybrids. What we observed was that while most of the cultivars reported as hybrids tended to have lower fertility, there were several that had exceedingly high seedling production, equal to or greater than classic B. davidii cultivars such as ‘Black Knight’ and ‘Nanho Blue’.

The take-home message is that we cannot automatically assume that Buddleja hybrids will be sterile. We therefore should test all plants.

That is the evaluation portion. I feel that we have gained a good handle on what is in the industry and where there are gaps. In 2022, we shifted from evaluating to improvement. The primary areas that we are starting with are breeding for dwarf yellow and dwarf “black” or intense dark purple.

Of course, seedlessness is a must-have in any introduction. I am fortunate to call Dr. Denny Werner a friend and mentor. He is responsible for such introductions as ‘Blue Chip’, ‘Blue Chip Jr.’, ‘Ice Chip’, ‘Pink Micro Chip‘ and ‘Purple Haze’ — all of which are seedless in addition to being beautiful.

Dr. Werner has shared with me some of his strategies to develop dwarf yellow cultivars over the years. The fact that one is still not out there is good evidence that it is a sticky problem. I make no promises that we will deliver quickly, but we have what I believe is a good strategy to fill these gaps in the available cultivars.

For butterfly bush, we are just getting warmed up. I’m excited to see where the road leads.

Fresh for 2023

Above I mentioned that we are in a bit of an inflection point. Woody plant breeding is a long-term endeavor. With time and observation, certain plants will rise to the top. Such is the case with a few plants we have been looking at for quite some time.

We have released a tetraploid form of Vaccinium ovatum (evergreen huckleberry) that has vigorous, upright growth. It’s a super-strong grower in tissue culture and in containers. This is an example of a plant that may not turn the world on its head, but has improved, if not solved, some of the production issues the species-type had. This selection will be offered by Briggs Nursery.

Mock orange is a love of mine. They may only flower for a short time, but the fragrance is utterly divine. I have been using some of the species that, with some refinement, really make heads (or noses?) turn. I have made many interspecific crosses and been pleasantly surprised by the improvements possible with a single generation.

While I’m looking forward to some more novel introductions, it may be somewhat unsurprising that the first introduction from my lab resulted from an elite × elite cross. Swan Lake® (Philadelphus ‘ORSTPHILx1’ PPAF), which resulted from a cross of Philadelphus coronarius ‘Icezam’ (Icelandic™ Mockorange) × P. lewisii ‘Blizzard’, is available exclusively from Monrovia. (For more information, please visit https://www.Monrovia.com/Mock-Orange-44290.html).

The promise of triploid maples

Each year I provide an update on these seedless triploid maples that we have been working on. I fear some folks start to view this effort like the cliched “free beer tomorrow” sign you may see in your favorite watering hole. However, progress is moving steadily ahead.

I have made hundreds of observations of flowering of Acer ginnala (A. tataricum ssp. ginnala) triploids and have yet to find a viable seed. That does not mean that I can unequivocally state they are never going to set seed, but it is a very strong indication that we have reduced fertility sufficiently such that they are not an ecological threat. Still, there is more testing to be done.

We have been collaborating to increase numbers in micropropagation and then take through the production process. By the time of publication, I expect we have a few hundred that will be acclimated and growing on in containers and field plots around the West.

Remember above when I stated that “hope springs eternal”? Keeping that in mind, I would love to see one of my triploid Amur maples in production by 2025.

Norway maple triploids are also on the way. This species is more reluctant to flower — none of the triploids have flowered yet — but I have moved ahead with getting one accession into propagation for production and replicated trials.

It is more challenging in micropropagation and overall more of an unknown as far as how it will grow out after acclimation compared to Amur maple. To address that, we are starting the process early.

We have 100–150 that will be acclimated in 2023 to evaluate production scheduling and outplant growth. Assuming things go well, we will have replicated plantings to evaluate when they flower to provide necessary data on seed set, or lack thereof.

Growing Knowledge from the July 2023 issue of Digger magazine | Download PDF