The November issue of Gardens Illustrated featured a plant profile on Sorbus.  This genus includes about 100 species of trees and shrubs, which go by a variety of common names such as mountain ash, rowan, and service tree.  While the magazine highlights the many desirable traits of Sorbus, such as their multi-season appeal, this genus thrives in the United Kingdom but does not do well in Pennsylvania due to the heat and humidity of our summers.  However, there is one species of Sorbus at the Scott Arboretum that does succeed in this climate: Sorbus alnifolia.

The attracitve white flowers of Sorbus alnifolia. photo credit: T. Rounsaville

Commonly known as Korean mountain ash, S. alnifolia shows off gorgeous characteristics year-round.  In April and May, it produces beautiful white flowers.  From September through November, this tree stands out with stunning fall color of vibrant red, deep orange, and yellow.  Clusters of red fruit attached to pedicels persist throughout the winter months, showcasing an impressive bounty of berries.

Red berries of Sorbus provide winter interest in the BioStream. photo credit: L. Stiebitz

Hardy in Zones 4 through 7, this particular species is more resistant to the diseases that often impact Sorbus such as fire blight and leaf spot.  In fact, Sorbus alnifolia has been deemed a Gold Medal plant by the Long Island Gold Medal Plant program.  Korean mountain ash is also planted along the streets of Swarthmore.

Sorbus alnifolia was previously featured in the Plant of the Week posts by Josh Coceano.  Here you can see its showy fall color and attractive fruit.

Sorbus alnifolia in fruit. photo credit: J. Coceano

Korean mountain ash does best in well-drained soil and prefers full sun.  With a moderate growth rate, it can reach a height of 40 to 50 feet.  At the Scott Arboretum, you can see this gorgeous gem of a tree situated between the Biostream and Willets Residence Hall.

This asparagus caught my eye with a deep yellow fall color dotted with brilliant red berries. Native to Siberia, this edible perennial is dioecious, requiring male and female plants to produce those attention-grabbing berries. The foliage of Asparagus schoberioides has a flowing and frilly texture. Chuck notes that “it reminds me of Amsonia hubrichtii in texture.” In our trial of Asparagus schoberioides, average well drained soil in sun to part sun keeps it happy.

The flowing, frilly texture of Asparagus schoberioides dotted with vibrant red berries. photo credit: R. Robert

We sourced our Asparagus schoberioides plants from John Story of MeadowBrook Farms. MeadowBrook received their plants from Chanticleer, who originally sourced them from a plant expedition trip by the Morris Arboretum. Interestingly, Chuck initially discovered this attractive plant outside of the Visitor Center of the Morris Arboretum. Apparently, Asparagus schoberioides has caught everyone’s eye as we are all experimenting with it to determine if it will be a good garden plant.

I offer this plant to spark your daydreaming of perfect gardening weather and great gardening ideas. I encourage you to consider what plants you will trial in your garden in this year. And don’t worry, I will let you know if Asparagus schoberioides proves to be a worthy ornamental plant after our trial is complete. Happy daydreaming.

Buxus sempervirens 'Vardar Valley' is a PHS Gold Medal winner. photo credit: J. Coceano

The evaluation process is relatively simple.   We evaluate for “grower friendliness” on a scale of 1 to 5 with 5 being “easy” and  1 being “difficult,” and “impulse cosmetics” with 5 being “wow” and 1 being “ugly.”  We also record additional comments which often include notes on pest and disease problems.

Buxus sempervirens 'Newport Blue' has an attractive rounded form. photo credit: J. Coceano

For the 2011 National Boxwood Trials the following boxwoods received 5 in both categories in our trials: ‘Dee Runk’ and ‘Pyramidalis’ are beautiful upright cultivars.  ‘Jensen’ is a dwarf clone. ‘Vardar Valley’ is a PHS Gold Medal recipient. ‘Longwood’ and ‘Newport Blue’ are good rounded forms.

Buxus sempervirens 'Longwood' is also ranked highly as a rounded form of boxwood. photo credit: J. Coceano

Saunders Brothers, who specialize in boxwoods, have developed the National Boxwood Trial program by establishing official sites for evaluation. Trial sites are located throughout the United States and international gardens including Tbilisi Botanical Garden in the Republic of Georgia; Nikita Botanical Gardens, Ukraine and Langely Boxwood Nursery in England.

Buxus sempervirens 'Jensen' is a dwarf clone. photo credit: J. Coceano

In the United States, the 60 institutional trial sites are divided regionally including Northeast, Mid-Atlantic , Southern, and Midwest Regions.  The Scott Arboretum has been a participant for many years as part of the Northeast Region.

Buxus sempervirens 'Dee Runk' is a beautiful upright cultivar. photo credit: J. Coceano

Copies of this 129-page color report are available for $20.00 each.  Make your check payable to National Boxwood Trials and send to 2717 Tye Brook Highway, Piney River, VA 22964

As the leaves fall and vibrant colors fade, the stalwarts of the garden take center stage. Blending pleasantly into the background during the growing season, evergreens provide that splash of green we seek in the dreary winter months. A staple found in many gardens for this winter green is juniper.

The bronze gold foliage of Juniperus x media 'Old Gold'. photo credit: R. Robert

Junipers come in variety of sizes, habits, and colors. Named for its bronze gold foliage, Juniperus x media ‘Old Gold’ holds its unique color through the winter months. Placed in full sun, the thin needles appear as golden yellow lace-like foliage as new growth.

Juniperus x media 'Old Gold' planted along loading dock entrance of McCabe Library. photo credit: R. Robert

This low/medium height shrub serves well as a foreground planting or colorful accent. A mass planting screens the loading dock to the McCabe Library on campus.

‘Old Gold’ responds well to trimming and can be maintained at a variety of heights and shapes. These trimmings provide a great accent of color in arrangements or in your holiday wreath. The touch of gold contrasts well with the blue tones of Juniperus virginiana ‘Grey Owl’ in green wreath created at the Scott Arboretum.

Green Wreath Workshop participants use various textures and colors to create striking wreaths. photo credit: R. Maurer

Experiment with the subtle color tones of ‘Old Gold’ during the Green Wreath Workshops at the Scott Arboretum from Thursday, December 1^st to Saturday, December 3^rd. Take home this and other great accent greens at the Holiday Green Sale on Saturday, December 3^rd from 10 am to 2 pm.

Colorful array of magnolia fruit collected from the Scott Arboretum, Henry Foundation, and Morris Arboretum. photo credit: J. Coceano

We have gathered seed from the Arboretum’s collections, as well as from the Henry Foundation in Gladwyne and the Morris Arboretum in Chestnut Hill.

Stack of follicles bursting with magnolia seeds. photo credit: J. Coceano

Most magnolia seeds are found in large cone-like fruits called follicles.

Magnolia seeds removed from follicles and ready for soaking. photo credit: J. Coceano

Once the follicles open up and reveal the seed which is often red and covered in a waxy coat, the seed can be harvested.

Once removed from the follicles, seeds are soaked for three days. photo credit: J. Coceano

After the seeds are harvested, they are soaked in water for three days in order to loosen the seed coat. Our volunteers found the most effective way to remove the seed from the seed coat after soaking was to squeeze the fruit. The seed simply squirts out of the fruit.

Cleaned seeds are allowed to dry for a day. photo credit: J. Coceano

The seeds are then dried for a day or two. The seeds are packaged in slightly moist vermiculite and refrigerated. Do not store the seeds dry, because they rapidly lose viability under those conditions.

Arboretum Assistant (volunteer) Marianne DiPaulo packages seeds in moist vermiculite. photo credit: J. Coceano

The moist seeds are stratified for 2 to 4 months at 32 to 41 degrees Fahrenheit before planting. You can also fall- plant the seeds outdoors to allow nature to provide the cool, moist conditions for stratification.

Throughout the process it is important to keep the name and the source with the seed.  Those who subscribe to the Magnolia Society’s seed exchange will make their selections based on species and source. To learn more about the Magnolia Society International and to participate in the seed exchange go to: www.magnoliasociety.org.  Also, consider attending the next annual meeting in the Bay Area and Sonoma Valley.

As a whimsical aside on the wonders of seed germination, enjoy this video of our former summer intern, Jared Barnes impersonating our favorite super hero, Superseed. Happy propagating!

Symphyotrichum oblongifolium 'Raydon's Favorite' blooming in the Wister Parking Lot. photo credit: R. Robert

We appreciate this aster in the garden because it is the most reliable native perennial aster with a consistently striking floral display from September to October. The daisy-like, lavender flowers attract fantastic butterflies and bees. ‘Raydon’s Favorite’ also does well as a cut flower, and it has become a favorite of our flower arranging volunteers too.

It has been noted that ‘Raydon’s Favorite’ is unscathed by drought and/or excessive rain as we experienced this summer/fall. Plant in typical garden conditions of sun with well-drained soil for best results. Another great aromatic aster is  ‘October Skies’ for its more compact form.

Star-shaped flowers of Chionodoxa forbesii 'Pink Giant'. photo credit: Brent and Becky Bulbs

Chiododoxa forbesii ‘Pink Giant’ reaches only  6 to 8 inches tall.  However, the flowers are relatively large for a Chionodoxa.  The star-shaped, six-petaled flowers are bubblegum-pink and skyward facing.

At the Arboretum, we have used Chionodoxa among other “smaller bulbs” in the Harry Wood Garden.  In the panels at Wharton Courtyard, they create a groundcover of pink just as the magnificent saucer magnolias, Magnolia x soulangiana are coming into flower.

The bubblegum-pink flowers of Chionodoxa forbesii 'Pink Giant'. photo credit: Brent and Becky Bulbs

Unlike tulips, crocus, and hyacinths, all Chionodoxa are deer resistant.  Plant these bulbs three inches deep before early November.   They can be planted among other bulbs but also do well amid deciduous herbaceous plants such as Epimedium, Hosta, and Tiarella.

Members of the Scott Arboretum will receive this delightful bulb as their fall dividend at the Fall Festival on Saturday, October 15 at 4 pm. Become a member today to add this bulb to your garden.

Scott Arboretum Curator Andrew Bunting cautions, “Eye-catching flowers can pull us in as if we were another pollinator, but we don’t want to limit our garden shopping to just buying at the big bloom time for a particular plant. Sure, a flowering plant makes an appealing nursery display, but purchasing plants only when they are in bloom is not a good strategy. You can, however, think ahead. Look at typical bloom times for your region, and easily chart out your selections with the aim of having a good seasonal flow of flowers.”

We asked Andrew to fill in a calendar with monthly examples of signature flowering shrubs. Here are Andrew’s picks for a “book-of-hours” monthly approach to illuminating your garden:

The silky white buds of Edgeworthia chrysantha open to a mass of tubular yellow fragrant flower. photo credit: R. Maurer

March Edgeworthia chrysantha – This is my favorite shrub for early spring flowering.  In late March, the silky white buds will open revealing masses of tubular yellow fragrant flowers.

April Fothergilla gardenii ‘Suzanne’ – ‘Suzanne’ is a diminutive selection of the fothergilla.  Before the leaves emerge, this shrub is adorned with fragrant, white bottlebrush-like flowers.

May Calycanthus x raulstonii ‘Hartlage Wine’ – ‘Hartlage Wine’ is one of the most exciting shrubs for spring flowers.  As the leaves are emerging, this Calycanthus is covered in large open-faced maroon flowers.

June Hydrangea paniculata Little Lime^TM – This is the dwarf version of H. ‘Limelight’, reaching only five feet tall at maturity. In June, cones of lime green flowers will emerge, turning white for the remainder of the summer.

Emmenopterys henryi is a great tree for a show stopping display in July. photo credit: D. Mattis

July Emmenopterys henryi – Emmenopterys is an exciting tree for its July flowers.  The large white bracts look as if they are hovering above the foliage.

August Lagerstroemia indica [Burgundy Cotton®]=’Whit VI’ – The crepe myrtles are a quintessential summer flowering tree.  This new selection contrasts beautifully its purple-black foliage with white flowers.

Disanthus cercidifolius' heart-shaped leaves backlit by the setting sun. photo credit: D. Mattis

Fall Color Disanthus cercidifolius – Many shrubs have outstanding fall color.  Disanthus has spectacular fall color.  Depending on the siting, the heart-shaped leaves can vary from fire engine-red to reddish purple.

Late Fall Ilex verticillata ‘Maryland Beauty’ – ‘Maryland Beauty’ is one of the finest clones of winterberry hollies.  From September to March the branches are heavily laden with cherry–red berries.

The attractive bark of Acer triflorum provides winter interest in your garden. photo credit: R. Maurer

Winter Our gardens do not end with a killing frost.  There are many plants that continue to provide interest on through the winter, including those with attractive bark, like Acer triflorum.  This small maple has a depth of orange-brown colors in its flaking bark and makes a great specimen tree.

Crytomeria japonica 'Yoshino' attractive pyramidal shape looks lovely with this light dusting of snow. photo credit: R. Robert

Of course, conifers stand out in winter, and Cryptomeria japonica ‘Yoshino’ is a great choice. This cultivar of Japanese cedar holds its color well in winter, has a strong pyramidal shape, and sheds snow well. It grows tall and fast in the sun, but will also perform in shade, just growing more slowly.

The eye-catching flower display of Hamamelis x intermedia 'Jelena' adds to your winter garden. photo credit: R. Manduca

However, our discussionis about eye-catching flower displays, and there are plants to brighten up the dead of winter with blooms—witchhazels, in particular. Hamamelis x intermedia ‘Jelena’ is a great choice. It has a copper-colored flower, rewarding close inspection because it’s also fragrant.  ‘Jelena’ generally sheds last-season’s leaves, so those blooms are not obscured, which happens with some witchhazels.

You can get full descriptive and cultural information on the plants Andrew mentioned from the Plant Sale Handbook. All these plants will be available for sale at the 2011 Scott Associates Plant Sale.

Another good resource to help you plot peak bloom times is this table at the Missouri Botanical Garden website. The calendar charts blooming for their area of the Midwest, but their USDA hardiness is comparable to our region.

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Ted Patterson, from Wayne, PA, retired from public relations work with the U.S. Dept. of Agriculture, is a co-chair of the woody plant section at the Scott Associates Plant Sale.

With patience, the swamp white oaks of Magill Walk have matured into a striking alley. photo credit: R. Maurer

“Some components of a garden design offer an instant hit or they hit the ground running,” says Scott Arboretum Curator Andrew Bunting. “But there are plants where it takes a bit of patience for them to fully realize their true attributes. And that is really the ultimate gratification for a gardener—to nurture a plant through a number of seasons and see its development unfold.”

With that philosophy in mind, and in keeping with our 40th anniversary theme, Andrew identified some examples of plants that reward patience:

Wonderful fall color of Acer triflorum. photo credit: M. Blandford

Acer triflorum will develop into a beautiful small specimen tree with tawny peeling bark and wonderful sugar maple-like fall color.

Camellia japonica ‘Korean Fire’ is a perfectly hardy selection for the Delaware Valley.  Over time it will reach 15 feet tall and will be adorned in early spring with deep red flowers.

Cedrus deodora 'Silver Mist' has lovely silver-green foliage. photo credit: J. Coceano

Cedrus deodara ‘Silver Mist’ will develop into a majestic specimen conifer with silver-green foliage and arching branches.

Cercidphyllum japonicum ‘Morikawa Weeping’, a weeping form of katsura, becomes more and more elegant with time.  The long weeping branches create a stunning cascading habit with remarkable golden fall color.

Chionanthus retusus ‘China Snow’, like all Chinese fringetrees, becomes more and more spectacular with age.  At maturity it will reach 25 feet tall with an equal spread.  In May it will be adorned with feathery white flowers.

The distinquishing white bracts of Davidia involucrata. photo credit: R. Maurer

Davidia involucrata ‘Sonoma’ is a relatively new selection of the dove tree, which has larger than normal white bracts.  Davidia is unequaled for its significant flowers in the spring.

The white bracts of Emmenopterya henryi. photo credit: D. Mattis

Emmenopterys henryi remains one of the rarest trees in cultivation. This upright tree requires at least twenty years of growth before it comes into flower, but once this occurs you will be treated to stunningly large white bracts in July that look as if they are hovering over the branches.

Stunning fire-engine red fall color of Franklinia alatamaha. photo credit: R. Maurer

Franklinia alatamaha is a plant for all seasons.  In the summer, it is covered with large, white, camellia-like flowers; the fall color is a stunning fire-engine red; and the stems have interesting grey and white striations for winter interest.

Magnolia virginiana var. australis 'Henry Hicks' has intensely fragrant flowers. photo credit: ML Gessel

Magnolia virginiana var. australis ‘Henry Hicks’ was selected by Scott Arboretum’s own Dr. Wister because this sweetbay magnolia is nearly evergreen in the Philadelphia area.  Sporadically throughout the summer it has intensely fragrant flowers and is one of the few magnolias which will tolerate wet soils.

You can get full descriptive and cultural information on the plants Andrew mentioned—indeed on all selections, in advance—from the Plant Sale Handbook.

A final note on patience:

Biggest is not always best when it comes to purchasing plants. Large multi-gallon container plants or balled-and-burlapped plants do not necessarily succeed better than smaller container plants. All transplants take time to settle in and establish a good root system. A small container plant may have a quicker period of root adjustment, and after a few years of growth it may be equal in size to its multi-gallon cousin.

Plant experts helps shoppers at the Scott Associates Plant Sale choose the best plants for their garden. photo credit: J. Goren

Read about planting a tree on page 57 in the Plant Sale Handbook or discuss planting methods with a plant expert at the 2011 Scott Associates Plant Sale. We want your gardening patience to be rewarded.

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Ted Patterson, from Wayne, PA, retired from public relations work with the U.S. Dept. of Agriculture, is a co-chair of the woody plant section at the Scott Associates Plant Sale.

A comical moment at the Plant Sale with Eve Thyrum and her husband, Per. photo credit: D. Mattis

I consider connoisseur plants to be:

• rare new plants that are available only through small specialized nurseries, or
• hard to find choice plants long known in horticulture literature but rarely available in the trade.

Below are some wonderful examples of connoisseur plants, all of which I have grown except for Aesculus wangii.

Choysia 'Aztec Pearl' in bloom. photo credit: Scott Arboretum Archives

Choisya ‘Aztec Pearl’ – I actually love this plant just before its pearl-like flower buds open.  Clusters of pinkish round buds, set against finely cut, trifoliate leaves, appear as bursting fireworks and add just as much ornamental value as the highly fragrant, almond-scented corymbs of white flowers that follow.

Deutzia sechuenensis var. corymbiflora – I’ve been growing this long-blooming, rare shrub for at least 10 years and without fail, every late spring as I walk by this plant, its beauty beckons me to observe closely its numerous sprays of starry, white flowers.  I then comment to myself, wow after all these weeks, I can’t believe it is still in full bloom and looks so perfectly beautiful!

Edgeworthia chrysantha ‘Akebono’ – One of my most prized plants in the garden – I love its scaffolding architecture of thickly rounded, smooth, tan branches which are adorned with plumeria-like foliage.  I prune to keep it open.  After foliage drop in late fall, flower buds emerge, quickly becoming fuzzy, silvery and fat, and then opening to a fragrant display of cinnamon-red flowers.  Definitely plant it near a window or walkway to enjoy during the winter months.

Bright red petioles of Emmenopterys henryi. photo credit: D. Mattis

Emmenopterys henryi – It’s rare in the forests of China and probably rarer in cultivation.  Supposedly taking many years to flower, two trees have recently bloomed at Quarryhill Botanical Garden in California after only six years.  So my hope to see it in flower spurs me on to adoringly appreciate this tree – it’s the anticipation!  Right now I’m enjoying its large, lush, dark-green, highly textural foliage with its bright red petioles.

The attractive shrub Helwingia japonica 'Golden Boat'. photo credit: R. Robert

Helwingia japonica – I planted this shrub just to observe its unique growing habit. Small clusters of ivory flowers emerge smack dab in the middle of each leaf.  Unfortunately I do not have both sexes: for if I did, I would then be able to enjoy the black berries which appear as if glued onto each leaf.  To ensure berries, plant at least 3 plants, or better yet 5, to increase your chances; these plants are always sold unsexed.

The elegant and charming shrub Platycrater arguta. photo credit: Scott Arboretum Archives

Platycrater arguta – Another prized shrub, quiet, elegant, and charming, even when not in flower.  Upon watching one grow at Scott, I was pleased to see it offered at the 2009 sale and I secured one immediately.  After 2 years, it has aged into a perfectly rounded shrub with a dainty, mounding habit and soft-spoken flowers.  This hydrangea relative has dangling clusters of white flowers.  Since it is on the subdued side, I prefer pairing it with other plants that feature texture over bloom, i.e., ferns, small hostas, and Solomon’s seal.

Aesculus wangii – This is a plant I don’t grow, but it is at the top of my list to bring home from this year’s sale. To quote Andrew Bunting “it’s the rarest of rare.”  Threatened by habitat loss in China and Vietnam it is on the International Union for Conservation of Nature and Natural Resources “Red List” as vulnerable.  So I feel compelled to plant one to preserve it from extinction.  It bears enormous, 18” long panicles of purple-spotted yellow flowers followed by 4” diameter seeds – how can I resist!

Selecting those connoisseur plants at the Scott Associates Plant Sale. photo credit: K. Bock

Good sources of connoisseur plants are typically specialty nurseries and arboretum plant sales including the Scott Associates Plant Sale, September 16^th through 18^th.

Finally, it’s the people, not the plants, who are actually the connoisseurs.  Anyone spending time in study and appreciation of plants can achieve some connoisseurship.  Most important is pleasure, and each of the many plants at the Scott Associates Plant Sale will bring you the opportunity for long-term appreciation.

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Eve Thyrum is an enthusiastic garden who has written for Fine Gardening, been featured in Southern Living, named member of the year for the Hardy Plant Society, and served as chair of the Scott Associates Plant Sale to name a few of her horticulture accomplishments. She also researches and authors all the Plant Fact Sheets for Scott Arboretum Horticulture Seminars. For the 2011 Plant Sale, she serves on the Education Committee.