Showing posts with label Clethra. Show all posts
Showing posts with label Clethra. Show all posts

One Sweet Clethra



Clethra has long been one of my favorite plants. I’m a sucker for fragrance and few plants pack more olfactory punch than Summer Sweet (Clethra alnifolia). If you’re a subscriber to my blog then you know that I’ve been breeding shrubs for about eight years now. The first plant introduced out of our breeding program was Summer Wine Ninebark (Physocarpus opulifolius). Since then I’ve introduced two new reblooming Hydrangea called Let’s Dance Moonlight and Let’s Dance Starlight, a compact Hypericum called Sunny Boulevard, Chardonnay Pearls Deutzia, Fine Wine Weigela, Ghost Weigela, and Incrediball Hydrangea. Vanilla Spice™ (Clethra alnifolia ‘Caleb’) is one of our newest introductions and at the moment is only available at wholesale as small liners. If all goes well you will see it at retail in the spring of 2010. Vanilla Spice, like all Clethra, has wonderfully fragrant flowers in late summer. Its foliage is dark, glossy and very attractive. Most remarkably this plant has flowers that are larger than typical. Each flower is roughly 30 to 50% larger than normal.

Vanilla Spice® Clethra

This native beauty is best when planted in a location where you can best enjoy its wonderful fragrance. I like to plant Clethra is large blocks to increase the fragrance potential. Ruby Spice is a special cultivar with reddish-pink flowers, so Vanilla Spice with its white flowers makes a nice companion for this favorite. While white flowers are not as exciting dark pink flowers, I am partial to white flowers. They simply show up better than red in garden, especially in the evening when I am typically in the garden.


Stay tuned, or better yet subscribe to my blog and have it emailed every time I post (Just click here). I will be sharing more new introductions over the next few posts.

Clethra: The Sweetest Summer Shrubs


I distinctly remember my first encounter with Clethra alnifolia (Summersweet or Sweetpepperbush). The air was thick with its spicy sweet fragrance and it begged me to search for it source. Tucked into the center of a large shrub boarder was a tall, gangly plant with small white spires about eight feet in the air. Not much of a plant, but it was obvious that it had never been pruned or cared for. Despite its poor habit, I felt that any plant that smelled that sweet deserved to be used. Some years later I specified Clethra in a landscape design. Of course I was a naïve greenhorn, too foolish to realize that it was not available in the trade for purchase. But I was smart enough to realize it was a plant worth growing.

Times have changed and so have our pallet of plants. Today Clethra is available to purchase at nearly every landscape pick-up yard, so are a host of improved cultivars. How is it that within a period of 25 years, so much can change?

It all started with Clethra ‘Hummingbird,’ the first dwarf form of Sweetspire. It was an obscure plant that Fred Galle of Callowway Gardens had discovered and for the most part had been forgotten. Then Richard Feist, a Callowway intern at the time, saw the plant and bells went off. With the permission of Galle he registered the plant as ‘Hummingbird’ and then wrote an article in Field Notes in American Nurseryman. All of a sudden Clethra was worthy. Clones started coming out of the woodwork; ‘Rosea’, ‘Pink Spires’, ‘Creal’s Callico’, ‘Fern Valley Pink’, ‘Hokey Pink’, ‘Cottondale’, ‘September Beauty’, ‘Ruby Spice’, ‘Sweet Suzanne’, ‘Sixteen Candles’, ‘White Dove’ and ‘Sherry Sue’ just to name a few.

While Clethra is relatively easy to fine these days, it is still greatly under used. In my travels to Europe, I am amazed that the plant has gained little respect; it is available only at collector type nurseries. How can it be?

Summersweet is an American native that can be found along the Eastern seaboard from Maine to Florida and west into Texas; along its western range it is native as far north as Tennessee. As a facultative wetland species is most likely to be found growing in low, moist woodlands, especially in the South, but in its northern range it is not unlikely to find the plant on higher, drier ground. You need not plant this shrub in a swamp to have success. My garden is nearly pure sand, and with the regular irrigation the plant grows just fine. Just remember that Clethra is not a plant for droughty soils. USDA zones 5-9.

Plant height varies greatly depending upon the cultivar. While the species can reach eight feet in height, cultivars such as ‘Hummingbird’, ‘Sixteen Candles’ and White Dove™ max out around three feet. Regardless of cultivar Summersweet benefits from pruning especially at a young age. Regular pruning creates a bushier, fuller plant as opposed to a leggy bare bottomed plant. Clethra alnifolia, especially the variety tomentosa can be suckering or stoloniferous. My observation has been that suckering is more prevalent in moist soils, while it is almost nonexistent on drier soils. Even where suckering is prevalent, it is never so aggressive that it presents a problem.

Flowers while typically white, can also be pink (‘Pink Spires’, ‘Hokey Pink’, ‘Rosea’) or near-red, dark pink such as ‘Ruby Spice’. The light pink varieties are quite attractive and should not be abandoned totally in favor of the darker ‘Ruby Spice’; even though the flowers may fade to near white as they age it is still a pleasing pink in the garden. The blooms appear in late summer; in Michigan we begin to see flowers in late July with August being prime bloom time. The cultivar September beauty™ extends the flowering season several week later than the other cultivars. Leave color ranges from a grey-green (‘Cottendale’) to dark green (Hummingbird, September Beauty, Sixteen Candles and White Dove™) with most other cultivars falling somewhere in between.

A check list of Cultivars:


‘Anne Bidwell’ - Panicle inflorescence with multiple racemes. Selected by Anne Bidwell.

‘Cottondale’ (var. tomentosa) - A selection with very large racemes up to 16” in length and grey-green leaves, suckering. Selected by Woodlanders Nusery.

‘Compacta’ - A very attractive selection with compact branching and a rounded habit of about 4’ in height. Selected by Tom Dilatush.


‘Creels Calico’ - A suckering plant with highly variable variegation. More of a curiosity than a landscape plant. Selected by Michael Creel.


'Fern Valley Pink' - Long, light pink flowers. Selected by Tom Clark.


‘Hokie Pink’ - Light pink flowers, more compact than typical. Selected by Jime Monroe.

‘Hummingbird’ - A low, compact, mounded plant maturing around 3’. Very dark green foliage and good yellow fall color. Selected by Fred Galle.

‘Pink Spires’ - Light pink flowers, matures at 6’-8’.


‘Rosea’ - Very similar to Pink Spires


‘Ruby Spice’ - A sport mutation of 'Pink Spires' with red flower buds that open to a rich pink. Does not fade to white. Very good yellow fall color. Selected by Andy Brand.


‘Sherry Sue’ - Typical white flowers, young stems are an attractive cherry red. Brought to us from the J.C. Raulston Arboretum.

‘Sixteen Candles’ -A seedling of Hummingbird with tight growth and larger white flowers. A fine plant selected by Mike Dirr.

Sweet Suzanne’ - Another seedling of Hummingbird with large flowers. Has been a weak grower for us, not as good as above. Selected by Mike Dirr.

var. tomentosa -A suckering plant with grey green leaves. ‘Cottondale’ is a superior selection

White Dove™ - Another seedling of Humingbird, Compact habit and larger white flowers. Selected by Flowerwood Nursery.


Related Species:


Clethra acuminata: Cinnamon Pepperbush - A small tree or larges suckering shrub at 12-15' in height. White flowers borne in termial racemes, with only slight fragrance. Attractive cinnamon colored bark. USDA Zones 6-8.


Clethra barbinervis: Japanese Pepperbush - A small tree or large shrub 15'-20' in height. White, fragrant flowers in terminal panicles in mid-summer. Superb exfoliating bark. An excellent plant for USDA Zones 6-7.


Flowering Shrub Evolution


As the Product Develop Manager at Spring Meadow Nursery my main responsibility is to identify new and superior plants for the Proven Winners ColorChoice flowering shrub line. These are exciting times for me because never before has so much effort been put into the development of shrubs. Breeders, nurseryman and even amateur gardeners have begun to see the potential of shrubs and are actively seeking improvements. In my opinion the results are amazing. These new plants are changing the way we garden, landscape and produce plants. Long thought of as the “bones” of the garden, shrubs are now the ornamentation too. Once the backdrop for perennials and annuals, a new breed of flowering shrubs have proven themselves as colorful and as showy as any herbaceous plant.

Think for a moment about how Endless Summer has changed the way we view Hydrangea or how Wine & Roses has influenced our old perception of Weigela as a one season plant. These are but a few of the better known examples but there are many more subtle, yet significant changes taking place over a wide range of species. Growers and Retailers need to understand these changes if they hope to benefit and meet demand. For example when I googled the plant name Leptodermis oblonga three years ago I got zero responses. Today I got 1,710 references including long discussions about the plant by gardeners communicating in forums. Did you know this great little shrub that blooms all summer long? Obviously the word has gotten out to gardeners.

Not all of the plants causing shifts in the market are new. Some have been around for years but because of changing times have found an audience. Concorde barberry was an obscure little plant developed at Wavecrest Nursery in Fennville, Michigan. Now with the increased interest in invasive species and as the problems encountered on the East Coast mount, ‘Concorde’ turns out to be a winner. Not only does it have great rich purple leaf color and a dwarf mounded habit, it is also environmentally friendly, hardly producing a seed. It turns out there are many environmentally safe alternatives when we start looking at the cultivars we currently grow. This niche will get even larger as researchers begin to introduce new sterile cultivars. They’re coming, but will states ban them before they are introduced? Let’s hope not.

What’s driving this explosion of new and improved shrubs? First, there is intense competition at retail. Savvy independent garden centers know they have to differentiate their stores from the big boxes. New and improved plants are a clear strategy to set a garden center apart from the chains. Big box stores have been more concerned about price than the actual product. They won’t pay extra for superior genetics because they don’t understand plants in general. Heck, many have not yet figured out that plants need water to live. The point is that independents understand what makes a good plant and they are actively looking for new products to compete and win in the marketplace.

The second driving force behind new plants has been the increased use of plant protection. Plant breeders can now make a return on their breeding investment. Canada has a new breeders’ rights law and Europe now has EU wide breeders’ rights system. In the U.S., people who have long opposed the plant patent system now see that patents, if used properly, can benefit everyone. Open licensing and returning a portion of the royalties to marketing the plants have created new value for breeders, growers and the retailers. And gardeners are getting better plants.

Another driving force behind the development of new shrubs was the rapid growth of the perennial market. Perennials helped to grow a new crop of gardeners, particularly women gardeners. Before perennials, the yard was mostly a man’s domain. As perennials came into vogue women learned that the garden could be more than just annuals and that gardening was not as complicated as the books and magazines make it out to be. As the perennial market matured, shrubs were the next natural step. After all shrubs are perennials, they just happen to have woody stems. The advent of container grown shrubs also helped the cause. Clean and reasonable in size, containerized shrubs met the needs of today’s gardener.

Lastly, success drives success. The success of new shrubs has awakened plant breeders, nurseries, retailers and gardeners to the value of flowering shrubs. Reblooming Viburnum, dwarf Clethra, ground covering Forsythia, yellow Spiraea, purple Sambucus, dwarf Buddleia and reblooming Syringa are just a few of the recent advances. It often starts with one new plant and builds rapidly. When I was in college some 25 years ago people laughed at me for putting Clethra alnifolia in a landscape plan. Then along came Clethra ‘Hummingbird,’ the first dwarf form of Sweetspire. It was an obscure plant that Fred Galle of Callowway Gardenshad discovered and for the most had part forgotten. Then Richard Feist, an Callowway intern at the time, saw the plant and bells went off. With the permission of Galle he registered the plant as Hummingbird and then wrote an article in Field Notes. All of a sudden Clethra clones start coming out of the woodwork; ‘Rosea’, ‘Pink Spires’, ‘Creal’s Callico’, ‘Fern Valley Pink’, ‘Hokey Pink’, ‘Cottondale’, ‘September Beauty’, ‘Ruby Spice’, ‘Sweet Suzanne’, ‘Sixteen Candles’, ‘White Dove’ and ‘Sherry Sue’ just to name a few. And so it goes with most species. Just wait until you see the next generation of reblooming Hydrangea macrophylla. Dr. Michael Dirr and breeders around the world are working like mad to improve upon Endless Summer. And so it goes, we are all winners because plants are improving at an exponential rate.

New and superior plants and the fundamental changes taking place in the market represent opportunities for nurseries and garden centers. There is real unfulfilled demand for superior varieties and consumers are willing to pay extra for them. The most commonly asked question I hear from retailers and from gardeners is “Where can I find them?”

In my next post I will list some plants that have had or will have a significant impact on the shrub market. These plants are changing the way we view shrubs. Check back next time and find out how many of these plants you know.