“Roses are red; violets are blue.”

These words date back to 1590, from Sir Edmund Spenser‘s epic poem, The Faerie Queene. Though classic, this poem may not have stood the test of time. Yes, many roses today are still red, as are many violets blue. But roses today run the gamut of colors, including blue(ish). In actuality, there is no such thing as a genuinely blue rose. But, this month’s Plant of the Month is as close as it gets.

Rosa ‘Veilchenblau’, also known by the names ‘Blue Rambler’, ‘Blue Rosalie’, and ‘Violet Blue’ is a vigorous multiflora climber-rose cultivar that was bred in Germany in the early 1900s. Known as one of the bluest of the old rambling roses, ‘Veilchenblau’ produces small, semi-double purple blooms that fade to blue with age. Its flowers grow on nearly thornless canes that can grow up to 15 feet tall by 12 feet wide. Flower color remains best when the plant is protected from midday sun.

Rosa 'Veilchenblau' photo credit: R. Maurer

Here at the Scott Arboretum, Rosa ‘Veilchenblau’ can be found in the Dean Bond Rose Garden, along with over 660 other roses that represent 200 different rose types. The Dean Bond Rose Garden will be showing beautifully all of this month and, at the end of May, will play a role in one of Swarthmore College’s beloved annual traditions. The morning of commencement, every graduating senior will have a freshly-cut rose from the garden pinned to their graduation gowns by one of the Arboretum’s staff or volunteers. We are happy to put our roses, such as Rosa ‘Veilchenblau’ (which happens to make a lovely cut flower!), to good use. But, don’t worry. Even after this special commencement tradition comes and goes, there will still be many roses left in the garden to visit and appreciate…in colors both red (like the old adage) and beyond!

Also enjoy a summer evening in the Dean Bond Rose Garden with good friends and refreshments on Thursday, June 18 for Sunset Sippin’: White Roses and Whirlwind Wit.

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One of the greatest joys of being a plant enthusiast, I think, is stumbling upon and having the chance to learn a new plant, especially one as unique and unusual as this month’s Plant of the Month. Edgeworthia chrysantha, known commonly as the paperbush or simply as Edgeworthia, is a largely unknown shrub, related to daphne. In my year with the Scott Arboretum, I’ve enjoyed observing how this deciduous shrub progresses through the seasons.

When I first saw Edgeworthia in the Isabelle Cosby Courtyard this past summer, it was covered with narrow oblanceolate leaves, forming a neat, round form, characteristic of edgeworthia. Towards the end of the summer, flower buds began forming at the branch tips of this specimen; these were the buds that were to serve as this spring’s flowers, the ones that are beautifully in bloom now. Moving into the fall-once the leaves of E. chrysantha fell-the large white flower buds provided ornamental value that lasted through the winter. And just last month, the edgeworthia buds began to open, revealing bright yellow, tubular flowers with a sweet fragrance. This is definitely a unique sight, one worth seeking out, and one that is on display now at the Scott Arboretum!

Edgeworthia chrysantha in Cosby Courtyard. photo credit: R. Maurer

The Edgeworthia chrysantha in the Cosby Courtyard is arguably the best specimen on campus, illustrating a nearly perfect form. However, another example of a mature edgeworthia plant can be found in the Terry Shane Teaching garden and two very small specimens can be found in the Harry Wood Garden and south of Martin Hall. To develop the best possible form, E. chrysantha should be grown in full sun. Our curator, Andrew Bunting, also suggests planting edgeworthia close to entryways or pathways, so that its spring fragrance can be best appreciated!

Come out to visit the Scott Arboretum this month, to observe this beautiful unusual plant as well as others!

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March’s pick for Plant of the Month is one of my favorite early blooming trees, Cornus mas, or the Cornelian cherry dogwood. Becky Robert, our Member and Visitor Programs Coordinator, wrote an informative article on Cornus mas for our blog last week, so I won’t reinvent the wheel here. Instead, I’d like to share a few added tidbits about this plant that is currently showing its colors at the Scott Arboretum:

• To best highlight the bright color of Cornus mas flower clusters, I recommend selecting a planting site near a dark-colored background, such as a building or dense conifer. This way, its bright yellow color will pop!
• As much as I enjoy the flowers of Cornus mas, my favorite aspect of the plant is the deeply red drupe-like berries it produces in the summer. While some people might find them unpalatable, I enjoy eating the berries straight off the tree; they remind me of the sweet-tart flavor of cranberries. An even tastier way to consume Cornelian cherry fruit is to turn it into a jam. Below is a recipe I’ve had success with. The jam tastes great on top of a good, crusty bread…just watch out for the pits and make sure the berries are fully ripe when picked.

4 cups of sugar

2 1/2 cups of water

1 pound of Cornelian cherry fruit

In a large pot, bring the sugar and water to a boil, stirring until the sugar dissolves. Simmer the liquid for 15 minutes. Stir in the fruit and simmer for an additional 30 minutes, or until the syrup has thickened. Periodically skim off the foam that comes to the surface of the mixture. Pour into sterile jars and seal (or consume right away to save that trouble).

• To provide some historical context to our Plant of the Month, here are some interesting facts:
  • The genera name, Cornus, is derived from the Latin word for horn, referring to the very hard wood of the dogwood
  • This hard wood was valued greatly by the Greeks, and it is said they used Cornelian cherry wood to make javelins and spearheads
  • In his 1914 publication, The Standard Cyclopedia of Horticulture, horticultural rockstar Liberty Hyde Bailey explains that dogwood trees get their common name because a medicinal extract from their leaves was used in England to wash mangy dogs.

Andrew Bunting discussing the virtues of Cornus mas 'Spring Glow'. photo credit: R. Robert

Whether you choose to eat its berries, make tools from its wood, wash your dogs in its extract, or simply admire its beautiful springtime blooms, Cornus mas is a great garden woody, one that I would recommend to any home gardener. Of course, if you cannot plant it at home, paying us a visit at the Scott Arboretum is the next best thing. We would love to see you here this Spring!

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The Scott Arboretum is in the unique position of serving a dual role, one as a public garden and the other as an active college campus. These dynamic roles drive many of the arboretum’s design decisions. For instance, as most of the student body is on campus during the winter months (as opposed to summer), we select plants with winter interest that can be appreciated by students during their daily campus travels. One such plant selection includes this month’s Plant of the Month, Jasminum nudiflorum, or winter jasmine. A late-winter beauty, I’ve heard Jasminum nudiflorum described as a necessary shrub for anyone with a winter garden.

I first noticed blossoms on our J. nudiflorum plants last week, after the pre-spring warm spell we experienced. Over the next month, more blossoms will continue to open all along the plant’s long, flexible bright-green arching stems. The end-effect will be a striking bright-yellow cascade effect, which can be seen along the retaining walls in our Winter Garden and to the north-west of Pearson Hall entrance to the John W. Nason Garden. This beautiful flower display serves as a nice reminder that spring is on the way.

Jasminum nudiflorum photo credit: R. Maurer

Introduced from China in 1844, Jasminum nudiflorum has been awarded the Royal Horticultural Society’s “Award of Garden Merit“. It is a versatile plant that can be trained as a climber across wires or a trellis. But, it is equally nice-looking if allowed to cascade down a bank or over a wall, such as the way we grow it here at the Arboretum. J. nudiflorum tolerates most soils. It grows well in part shade to full sun, but will flower more profusely in full sun. Its flowers, though beautiful, have no fragrance.

Come and see what else is blooming this month at the Scott Arboretum (our beautiful Hamamelis collection, Chimonanthus, Galanthus, some early Helleborus, the list goes on!). Even though it is still winter, we (and our plants) are hard at work…you won’t be disappointed!

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With a background in forest ecology, I’ve long been acquainted with the fall blooming habit of our native woodland witch hazel, Hamamelis virginiana. Every fall, I looked forward to seeing the witch hazel’s spidery flowers emerge, speckling the forest’s understory with yellow. It was not until entering the world of ornamental horticulture that I was introduced to a whole other world of witch hazels, one that includes winter-blooming witch hazels, such as Hamamelis mollis (the Chinese witch hazel), the species for this month’s Plant of the Month.

Hamamelis mollis offers us a bright burst of color during the winter. Four cultivars of the Chinese witch hazel can be found on the Swarthmore College campus, and the Scott Arboretum is responsible for the introduction of one of these cultivars, Hamamelis mollis ‘Early Bright’. The introduction of this cultivar occurred in 1988, selected for its exceptional, early bloom time. ‘Early Bright’ was first noticed by Steve Wheaton, Swarthmore’s former Director of Grounds. Over several years, he observed that one specimen, growing among a group of other Chinese witch hazels, consistently bloomed two weeks earlier than all the rest. With the help of our Curator (then Plant Recorder), Andrew Bunting, ‘Early Bright’ was named and registered by the Scott Arboretum.

Espaliered 'Early Bright' in the Theresa Lang Frangrance Garden. photo credit: Rhoda Maurer

At the arboretum, H. mollis ‘Early Bright’ has been observed blooming as early as the first couple of weeks in January; as of the day this post was written, the two in front of Swarthmore’s Papazian Hall were just on the brink of blooming. ‘Early Bright’ can also be found in our Witch hazel Collection and espaliered in the Theresa Lang Garden of Fragrance. In addition to its vibrant, golden-yellow color, the strap-like flowers of ‘Early Bright’-which bloom best in full sun-are sweetly scented.

Come out to the Scott Arboretum to beat the winter blues and see the Swarthmorean ‘Early Bright’. Julie Jenney, Education Programs Coordinator, will be leading a free tour on witch hazels and early spring blooms on Saturday, March 7 from 1 to 2:30 pm.

While I will always look forward to spotting the first fall-time blooms of our native witch hazel, now-during these winter months-I especially look forward to the advent of the beautiful blooms and scents provided by this Chinese witch hazel and others in our collection.

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While walking through campus last week on a cold, dreary day, I was pleasantly surprised to see the arboretum popping with vibrant colors and textures. In front of McCabe Library, I enjoyed the beautiful color displays of our red-berried deciduous hollies (Ilex verticillata). At the Harry Wood Garden, I delighted in the beautiful showing of delicate camellia blossoms (my favorite is Camellia oleifera ‘Winter’s Interlude’.) However, one of the most striking spots I came across during my winter stroll was in front of Sharples Dining Hall. Here, amid the richly textured bark of several paperbark maples (Acer griseum), I found a vibrant display of Cornus sericea ‘Cardinal’, the red osier dogwood, this month’s pick for Plant of the Month.

The red osier dogwood is certainly at its best this time of year. Arguably the most noteworthy feature of this multi-stemmed, deciduous plant is its brightly colored red twigs that reveal themselves once the plant drops its leaves. Especially on overcast winter days, this plant commands attention to passersby; it is even more striking against a snowy backdrop, a scene which we will likely have the chance to see one time or more again this winter.

Harmony of color and texture with Cornus sericea 'Cardinal' and Acer griseum (paperbark maple) in front of Sharples Dining Hall. photo credit: Miriam Pinsker

Cornus sericea has a wide geographic range; however, in warmer zones its twigs may appear more yellowish. The deepest red color occurs on new shoots and, over time, old stems can lose some color. Therefore, to ensure the best possible red twig color, it is recommended to renewal prune C. sericea ‘Cardinal’. This process involves selective thinning, by removing about 50 percent of its oldest stems in early spring. A more severe way to renewal prune is to cut the entire plant back every year, but this may be a more drastic approach than some home gardeners will want to take. Also, unlike last month’s Plant of the Month, Callicarpa dichotoma ‘Issai’, which flowers and fruits on new wood, C. sericea ‘Cardinal’ flowers and fruits on old wood. So, in your decision to prune or not to prune, keep in mind that there exists a trade-off between bright twig color and heavy flowering/fruiting for the coming season. Cornus sericea ‘Cardinal’ produces flat-topped clusters of creamy-white flowers in the spring, followed by small white-bluish fruits in the summer.

Cornus sericea is native to North American wetlands and stream banks; as such, this plant is best grown in rich wet soils, but it can tolerate a range of soils in full sun to part shade. Because of its wide geographical distribution, C. sericea has accumulated many common names over the years. Most commonly referred to as the red osier or red-twig dogwood in the Northeast, some of its other pseudonyms include: redstem dogwood, American dogwood, creek dogwood, kinnikinnik, squawbush, red willow, gutter tree, harts rouges, poison dogwood, shoemack, and dogberry tree! Regardless of what you call it, Cornus sericea ‘Cardinal’ is a great addition to a winter landscape. Stop by the Scott Arboretum this month to see this plant, as well as other winter-interest plants. Happy Holidays!

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Purple beautyberry, a deciduous shrub, is most striking during late autumn, when it drops its foliage for the season but holds onto its distinctive violet-colored berries as a key identifying feature. There are numerous accepted species of Callicarpa; however, the Pennsylvania Horticultural Society awarded Gold Medal status to Callicarpa dichotoma in the late 1980s, for its notably large berry clusters and gracefully arching branches. ‘Issai’ is best known for its early and plentiful fruit crop.

C. dichotoma ‘Issai’ is a fast-growing plant that prefers full to part sun; more sun exposure will result in heavier fruiting and better fruit color. The foliage, when present on the plant, provides a nice architectural appearance, because the leaves are oriented on a single plane rather than radiating all around the stem. Before producing its notable berries in early fall, C. dichotoma produces summer-time pinky-lavender flat-topped flower clusters (also known as cymes) above its structural foliage.

At the Scott Arboretum, we cut our plants back to twelve inches in March, since they fruit and flower on new wood. This is a way to keep the plant to maximum size of four feet. Callicarpa dichotoma ‘Issai’ specimens can be found around the periphery of the Nason Garden. P.S. – While you’re there, be sure to also take in the beautiful yellow fall display of Amsonia hubrichtii, the thread-leaf bluestar (it may not be purple, but it is yet another fall-time show-stopper).

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In my last post I focused on the nefarious weed, Pinellia ternata. So this month I’d like to balance things out and discuss a plant far more pleasing to the eye, Symphyotrichum oblongifolium ‘October Skies’ formerly known as Aster oblonifolium ‘October Skies’. At the Scott Arboretum, this aromatic aster cultivar graces the perennial bed of the West Garden and is also the newest addition to our naturalistic Biostream.

‘October Skies’ is a shorter, bluer, and bushier relative of S. oblongifolium ‘Raydon’s Favorite’, found in the Terry Shane Teaching Garden. While its cultivar name is said to be attributed to the deep blue hue of the autumn sky, I find the flowers of this aster to be more lavender than deep sky blue. Regardless of how you classify them, the colorful blooms of S. oblongifolium ‘October Skies’ look lovely in the fall garden. At a time when many garden plants have already seen their last flowers of the season, ‘October Skies’ provides a profusion of one-inch compound daisy-like flowers atop stems that grow about 18 inches tall.

Symphyotrichum oblongifolium ‘October Skies’ likes full sun and is tolerant of drought and poor soils. It requires very little care and spreads quickly by rhizomes. So although it is a shorter-than-average aster, ‘October Skies’ makes up for its lack of verticality with its impressive horizontal spread. The asters planted last fall at the West Garden, for instance, started out approximately eight inches wide; they now span over three feet!

While the flowers of the fragrant aster do not have a noticeable scent, their oblong, dark green leaves are fragrant when crushed. The plant is successful in attracting migrating butterflies, and other beneficial insects by providing useful nectar. This aster feature, in addition to attractive and easy-to-care-for qualities, make Symphyotrichum oblongifolium ‘October Skies’ a garden plant that receives my stamp of approval. Especially as cooler weather descends on the Philadelphia area, fragrant asters provide a nice reminder of the bright and cheery colors of summer. Visit the Scott Arboretum to see asters in bloom and to welcome the autumn colors.

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The volunteer who first introduced me to Pinellia described this invasive plant with a tone of loathing and detestation. If memory serves me correctly, I believe she described Pinellia as the “bane of [her] gardening existence.” At the time, I thought that was a pretty strong statement for such a small weed. But, after three months of first-hand experience with this seemingly ineradicable plant that always reappears with gusto, I now understand what the volunteer meant.

Pinellia ternata is native to Japan and is sometimes referred to as cow-dipper. The plant possesses trifoliate leaves and a flower typical to plants in the Araceae family (think of a jack-in-the-pulpit with its spathe and spadix flower). Similar to other Araceae plants, the flowers of Pinellia are hermaphroditic. One of the secrets of Pinellia ternata‘s success is that its stem regenerates from a corm that resides inches below the soil’s surface. As a result, hand-pulling is nearly always ineffectual in ridding a garden area of Pinellia. The best method I have found for dealing with Pinellia is to push a hori-hori (Japanese digging knife) or other digging tool deep enough in the soil (a few inches) to excavate the entire plant. Success is achieved if the removed plant still has a spherical corm attached to its long white stem.

P. ternata thrives in the mid-Atlantic region and, left on its own, is capable of nearly doubling in population every year. However, with consistent and accurate weeding, it is possible to control the spread and reduce the pervasiveness of Pinellia in your home garden. Just be sure not to dump Pinellia in your compost pile; instead, tie it up in a plastic trash bag to prevent it from spreading its weedy ways.

Until next time, good luck in your weeding adventures and happy gardening!

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Reflecting on my time so far as the curatorial intern (I just finished my second month here), I would say one of my favorite parts of the job is my daily interaction with Scott staff, volunteers, and visitors. Inquisitive visitors often stop to chat and ask me questions; if I were to tally all these questions, the top three would probably be:

1) “Excuse me – Could you please tell me how to get to the admissions office (Parrish Hall)?”

2) “Wow! What is that plant?” (Referring to Musa sikkimensis, our resident banana plant that we planted about 3 years ago and that we overwinter every winter)

3) “What is that odd-looking purple plant over there?”

The answer to this last question is our Plant of the Month, Angelica gigas or Korean angelica. This unique plant is a biennial that stands high at 3-6 feet tall, with purple, ribbed stems topped off with dark purple umbels. In its native homes of China, Japan, and Korea, angelica can be found in forests, grasslands, and alongside streams. In the home garden landscape, Angelica gigas offers a strong architectural form and a beautiful contrast when combined with finer-textured plants. It performs well in full sun to part shade, and prefers average to very rich soils. Angelica is difficult to propagate and its seeds do not store well, so it is best to leave angelica to self-sow and later edit out any undesirable plants. Bees, wasps, and butterflies love angelica’s fragrant flowers. Here at the Scott Arboretum, they are regularly visited by nectar-hungry wasps.

Beyond its aesthetic value, the dried root of angelica has been used for thousands of years as a valuable Chinese medicinal herb, said to aid heart, lung, and liver functions, as well as treat a number of women’s health issues. Today, in Korea, Angelica gigas is used to treat anemia. A recent Japanese pharmacological study even suggested a possible role that angelica’s essential oil could play in treating nicotine addiction. Angelica is not alone amongst garden plants possessing medicinal qualities. Hypericum (St. John’s Wort), Echinacea (purple coneflower and last month’s Plant of the Month), and Nepeta (catmint) species are said to possess a range of medicinal uses, making many gardens a veritable pharmacy! Come and visit us at the Scott Arboretum to see these plants and others…and when you do, be sure to stop and say hi (and maybe even ask a question!).

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