The Royal Horticulture Society Issues Final Report

About 150 years ago German physician and botanist Philipp Franz von Siebold introduced Hydrangea paniculata ‘Grandliflora’, the Pee Gee Hydrangea, from Japan to the Western World. For nearly a century, Grandiflora reigned supreme and was the only cultivar available to buy. It was so ubiquitous that people eventually came refer to the whole species as Pee Gee Hydrangeas.

Today the market has been flooded with cultivars and we have over 40 selections to choose from. I’ve grown most of these selections and have chosen my favorites. Limelight and Pinky Winky Hydrangea are most certainly the top two plants on my list. Well scientists at the Royal Horticulture Society in England appear to a similar opinion.

The Royal Horticulture Society just completed a five year evaluation of 47 Hydrangea paniculata cultivars. The results are in – Limelight and Pinky Winky (‘DVPpinky’) earned the highest rating of Excellent (3 stars) and both were awarded the prestigious AGM – RHS Award of Garden Merit. And how did Pee Gee fair? It received the lowest possible rating of no stars – (average to poor).

While I sincerely appreciate the time and effort the RHS put into this study - in the end this trial is kind of like those scientific studies that go to great lengths to prove what we already know.

A Better Boxwood

When it comes to determining if you have a better plant, it is essential that you know and understand the plants that are currently available. New plants must be trialed and compared in side by side tests with the best varieties to know what you have. If you can’t beat the best, then you better keep breeding until you get it right.

This side by side comparison of boxwood is a great example of the power of trialing plants. I’ve been growing and trialing North Star boxwood for over five years. When we first got the plant from its originator Gary Katerberg I was skeptical that his plant could rival the best boxwood varieties available. In fact, I did not give it much of any chance of being introduced. But when we had it in a test bed with twenty other varieties of boxwood, it preformed so well, the results could not be ignored. When you see it side by side with Green Velvet, the number one variety on the market, you can clearly see that it is a better plant. Even during winters with temperatures as low as minus 15 degrees, North Star boxwood shined; the winter and the spring foliage color was so much darker. While Green Velvet turned a pale pea green, North Star boxwood remained very dark. Additionally the plant is very compact, with dense growth, yet at the same time it grows faster than other popular varieties.

Clearly “Seeing is Believing,” and side by side trialing is the only way to find out if a plant is truly better or not. North Star boxwood has passed the test.

A Tale of Two Roses

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Just outside my office, growing side by side, are two excellent roses. Both are very free flowering and bless me with a continuous, summer-long display of red flowers. Each rose remains as clean as a whistle without the aid of sprays or chemicals. I suspect you're familiar with one of these roses. Perhaps you even grow it? It was developed Bill Radler and is called Knock Out.

But this is the story of the other rose. Its name is Candy Oh! Vivid Red and most likely you’ve never heard of it before. It was not developed by Bill Radler, however, it would not exist but for this well known rose breeder of the North.

At ripe old age of 13 David Zlesak read an article in the Milwaukee Journal that changed the course of his life. The article was about Bill Radler and how he hybridized new roses. Fascinated by the article and the idea of creating new plants, Zlesak wrote to Radler. To his surprise, Radler wrote back and this letter was the spark and inspiration that started David Zlesak on his plant breeding career and ultimately resulted in the rose Candy Oh! Vivid Red.

While working towards his PhD in plant breeding, David worked on numerous crops including small fruit, potatoes, Easter lilies and various perennial plant species. His first big breeding breakthrough came in 2006 when Proven Winners introduced Tuscan Sun Heliopsis a remarkable dwarf, continuous flowering perennial. Yet even though David found success in breeding other crops, his passion for roses never ceased - nor did his rose breeding. While other students were going to fraternity parties, David was up in his dorm room growing on thousands of rose seedlings under florescent lights. Out of these seedlings he selected the healthiest 1,500 plants and grew them out in garden plots he rented from friends and neighbors. Out of these, he selected the 50 healthiest, most floriferous plants. His selection process was further aided by the harsh Minnesota winters and the ubiquitous rose disease – black spot. Only the hardiest, most disease resistance roses remained.

Out of the thousands of seedlings that started out in his dorm room, David found that one seedling, a polyantha hybrid that stood out from all the others. It was vigorous, healthy and very floriferous. The vivid red flower color was so intense that it seemed almost to smolder in the summer sun. In 2008 David Zlesak introduced his first commercial rose selection - Candy Oh! Vivid Red.

That is the tale of two roses, and how Bill Radler had a hand in the development of both plants.

A New Pink Flowered Annabelle Hydrangea

Until now, the quest for a pink ‘Annabelle’ hydrangea was just a dream. Today the dream is a reality; introducing Invincibelle™ Spirit Hydrangea (Hydrangea arborescens 'NCSUHA1" ppaf, cbraf, pbraf), the first ever pink flowered Hydrangea arborescens with a mop-head flowers.

Sold by the millions, ‘Annabelle’ hydrangea is the most recognized and best selling hydrangea in the world. It is iron clad, blooms reliably and can be grown from Mobile to Manitoba. It is adaptable to many soil types and can be grown in full sun to fairly heavy shade. Pruning and care is a no-brainer. The only drawback - until now it only came in white. Everyone has been waiting for pink and now we have it!

Invincibelle™ Spirit hydrangea is the result of years of research, breeding and was developedment by Dr. Tom Ranney and his crew at North Carolina State University, Mountain Horticultural Crop Research Extension Center. This is a major plant breeding breakthrough! The flowers emerge a dark, hot pink color and mature to a rich clear pink. Soil pH does not influence the flower color. This plant will always have pink flowers regardless of the soil type.

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And if that was not enough, Invincibelle Spirit Hydrangea is continuous blooming! It continues to produces new flowers right up until frost. In fact, a single plant can produce 100 or more corymbs (flower heads) over the course of a summer.

Invincibelle Spirit Hydrnagea will be available at retail under the Proven Winners® ColorChoice® brand in spring of 2010. In addition the plant will help in the fight against breast cancer. Proven Winners will donate $1.00 from each purchase to The Breast Cancer Research Foundation® BCRF is dedicated to preventing breast cancer and finding a cure in our lifetime by funding clinical and translational research worldwide. (For more about BCRF, visit http://www.bcrfcure.org/part_corp_provenwinners.html

This new plant is useful as a specimen, mass planting or incorporated into perennial gardens or into a woodland setting. The blooms are extremely attractive both in the landscape and as a cut flower. It is a durable choice for both fresh and dried arrangements.

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Hardiness: USDA Zones 3-9 (perennial in zone 3)

Bloom time: Late May early June (earlier under poly). Reblooms until to frost.

Bud set: Blooms on new wood so it will flower ever year!

Bloom color: The flowers emerge a dark, hot pink color and mature to bright pink.

Quantity of blooms: Often 100 or more corymbs per plant over the summer

Branching habit: Freely branching with as many as 100 or more terminal shoots per plant.

Exposure: Full sun to partial shade

Growth rate: Moderate to Fast

Soil: Very adaptable, but proliferates in rich, well drained, moist soil. It is pH adaptable. Soil pH does not effect the flower color.

Pruning: In late fall or early spring. Blooms on new wood and tolerates being cut back to the ground.

Watering: If planted in full sun, sufficient moisture is needed. It will require additional watering on hot dry summer days until established. In South, should be planted in partial shade.

Wildlife: Habitat for songbirds and butterflies.

Native: Eastern United States. Florida to Maine. Kansas to Eastern Seaboard.

Type: Deciduous

Fertilizing: Fertilize in early spring by applying a slow release fertilizer specialized for trees & shrubs. Follow the label for recommended rate of application.

Uses: Groupings or masses, perennial or shrub borders, specimen, winter gardens.

Breeder: Dr. Thomas Ranney, NCSU. Mountain Horticultural Crop Research and Extension Center. Fletcher, North Carolina.

Learn more at http://invincibellespirit.net/

An Eye for Award Winning Plants

As I’ve said previously, one of the most satisfying aspects of hunting for and introducing new plants is getting affirmation that you’ve introduced a good plant. When growers and gardeners respond positively then I know my eye for a good plant is still working and on the right track. On that front, this last week has been a good one.

Just today I received a report from the Royal Horticulture Society at Wisley (England). They’ve been conducting an all European Buddleia trial that includes all cultivars available in the trade. That’s 107 different Buddleia cultivars in all, so the competition is very intense. In public voting this year, between July 31st to August 20th, , the top vote getters, by a decisive margin, were Buddleia x ‘Miss Ruby’ and Lo & Behold™ ‘Blue Chip’ respectively. The trial coordinator commented that the votes for Lo & Behold™ ‘Blue Chip’ would most likely have been even higher had the voting continued longer. That is because Lo & Behold™ ‘Blue Chip’ continued to flower well beyond all other cultivars. This is great news and is a good indication that each plant is in the running for the prestigious RHS award of Garden Merit. Dr. Denny Werner should be pleased that his plants took the top two spots. I expect that his breeding will garner ever more accolades in the future, as his Buddleia breeding is the best in the world.

I also got word that one of our new Oso Easy™ Roses won an award. The Rose Hills International Rose Trial awarded a Gold Medal to Oso Easy™ ‘Paprika’ as the Best New Ground Cover rose for 2008. Congratulations to Chris Warner and his outstanding breeding of disease resistant roses. Awards are nothing new to Chris. He has won over 100 international awards including two President’s Trophies and three Gold Stars.

Breeding a Better Spiraea

When evaluating a plant species, its cultivars and its future potential, I like to start by growing all the available cultivars in our test garden. This gives me a better understanding of the strengths and weakness of a species and each cultivar. It helps me to know how a new plant stacks up and if it has potential for release. It also helps us identify breeding opportunities.

After growing and evaluating every possible cultivar of Spiraea japonica, we came to the conclusion that there was an opportunity for plants with new and better flower color, better foliage color, improved mildew resistance and better branching. Feedback from our growers indicated they wanted more impulse appeal, mildew resistance, burn resistant foliage, more flowers. Lastly they wanted plants that required less care in production and in the landscape. With this information in hand we started breeding Spiraea.

After six years of breeding Spiraea and three more years of evaluation, we were able to narrow 1,500 potential field seedlings down to twelve candidates. We then propagated and grew on these twelve selections and evaluated them in production as one gallon and three gallons. Plants were also placed in our test garden and again compared to what was on the market. Additionally test plants were sent to key growers across the US to get their feedback. The most difficult part of the process is narrowing the selection down to one or two potential introductions. A cool wet spring made our task a lot easier. It was the perfect spring for powdery mildew. If a plant was going to get mildew, this was the spring. Mildew eliminated about half of the selections left in program.

By August two plants rose to the top as clear winners and were chosen for introduction under a series name call Double Play™. The name Double Play™ was chosen because each plant delivered two or more improved traits; primarily improved foliage and improved flower color. The first introduction is called Double Play™ Artist. This plant was a clear winner early in our field trials because it was compact, had attractive foliage coloration and unusual purple flowers. The foliage is unique because the new growth is a vibrant purplish-red color. As the season progresses the leaves mature to an attractive bluish-green color. The flowers also caught our attention. The flower color is a unique shade of rich purple that we’ve never seen before.

Double Play™ Gold is a dwarf gold leaf selection. It stood out from the other seedlings because it had no mildew, tight branching and a tidy dwarf habit, eye catching pure pink flowers and the plant did not burn when grown in full sun. This plant also stood out in our container trials, as each plant produced was a perfect little soldier with very little pruning.

Growers will begin producing the Double Play™ series next spring and I expect that will be at retail in Spring of 2010.

The Best In the West: Planting Hunting In Oregon

I've seen a lot of plants in the last five days; I've been in Portland, Oregon visiting nurseries and gardens. This is a great area to visit nurseries and see interesting plants, especially if you get into some of the smaller, more specialized nurseries. Here is just a few plants that caught my attention. What do you think?

Agastache 'Cotton Candy'

This plant is a sea of flowers. It's an easy growing, vigorous perennial that blooms from mid-summer until frost. The dense flower spikes have numerous light pink flowers. It has a compact, low branching growth habit. It tolerates dry conditions and prefers well drained soils. All Agastache are popular with hummingbirds.

Agastache 'Summer Love'

This new Hummingbird Mint has masses large red-purple flowers all summer and into fall. It forms an attractive upright mound to 36" tall and has bright green, fragrant foliage. This is a great perennial if you're in zone 6 or warmer and have good soil drainage.

Jasminum officinale 'Flona's Sunrise'

This colorful vine is a yellow version of the Poet's Jasmine vine. It is a strong climer that can reach twenty feet if you give is something to twine up. I especially like its fragrant white flowers in summer. It is hardy to zone 7 and warmer but those of you in Zone 6 might have some luck if you plant it in a protected location and mulch it each year to protect the roots.

Stokesia laevis 'Purple Pixie'

My friend and trusted Perennial Diva Stephanie Cohen turned me on to this little beauty. It is the first ever dwarf Stoke's Aster! It has large violet blue flowers and a short, compact habit that does not fall apart with maturity. It blooms in early July and sporadically until fall. It's a great little plant for the areas with high heat and humidity. Hardy to zone 5, it is happiest in full sun. It's best to avoid soils that are wet or high in lime.