Hydrangea arborescens ‘Annabelle’

Hydrangea arborescens ‘Annabelle’ provides dapples of blooms along the feet of Metasequoia glyptostroboides in the Metasequoia Allee. This deciduous shrub has a loose, open habit and typically grows 3-6’ tall. The large, rounded, white, sterile flowers which sit atop gray-brown stems bloom in June for about 2 months. Dark green leaves with light green undersides wrap the stems in an opposite pattern. The leaves turn yellow in autumn providing a colorful backdrop to the muted brown seed heads which can be a wonderful addition to a dried cut flower arrangement.

This classic hydrangea is easily grown in average, moist, well-drained soils in part shade. H. arborescens, also known as smooth hydrangea, can adapt to a variety of soil conditions with the exception of dry soils where its foliage tends to significantly decline. It is native to moist or rocky wooded slopes, ravines, streambanks, and bluffs making this a great plant for rain gardens and woodland gardens. Grown in zones 3-9, a more harsh winter may cause H. arborescens ‘Annabelle’ to die back to the ground. This is not a concern however, because the blooms are produced on new wood each season. Like many hydrangea species, H. arborescens ‘Annabelle’ is susceptible to bud blight, bacterial wilt, leaf spot, mold, rust, and powdery mildew. Also, watch out for aphids, mites, scale, and nematodes. Pruning the stems to the ground in late winter results in stem vigor and larger blooms, which helps combat pests and diseases. Photo credit: R. Armstrong

Hosta ‘Curly Fries’

My excitement when finding curly fries on a menu is comparable to my excitement when finding Hosta ‘Curly Fries’ in a garden. Hostas are an especially popular perennial because of their versatility in a landscape. A seedling from the usually sterile Hosta ‘Pineapple Upsidedown Cake’, the adorable, petit, mounded habit of ‘Curly Fries’ is a perfect choice for containers. This aptly named hosta can be found in a small container next to the side entrance to the Wister Center, surrounded by larger leafed blue hosta varieties.

A 2016 Hosta of the Year, this herbaceous perennial grows best in moist, well-drained soils with an acidic to neutral pH. While most hostas are grown for their large leaves, this little arching, wiggly clump is best planted where its small characteristics can be viewed easily.

Incorporating ‘Curly Fries’ into a miniature plant collection or into the front of a perennial border will showcase its color and form. Also known as plantain lilies, the unique pop of color from Hosta ‘Curly Fries’ exhibits best with morning sun exposure and afternoon shade. The stiff, narrow leaves are heavily ruffled, emerging chartreuse, eventually brightening to yellow. Considered a miniature, Hosta ‘Curly Fries’ matures to 6 inches tall by 16 inches wide, developing red speckles on the petioles and lavender flowers atop the clump in midsummer. Photo credit: R. Armstrong

Poliothyrsis sinensis

Seemingly perched atop the old observatory at the Cunningham House is Poliothyrsis sinensis, more commonly known as a pearl-bloom tree. Flowering from August to September, this showy, fragrant tree compliments the blooming hydrangeas and crapemyrtles at its forefront. P. sinensis are best grown in rich to medium moist, well-draining soils and become drought tolerant once established. Grown in full sun to part shade, this tree will reach a mature height of 30-40’ and spread to 15-25’. Pearl-bloom tree is hardy to USDA Zones 6-7 but may survive winters in Zone 5 if sited in a protected spot.

Poliothyrsis sinensis is the sole species within the genus Poliothyrsis. It was first discovered growing in China in the late 1800’s and was eventually brought to the Arnold Arboretum in 1908. As part of the family Salicaceae, P. sinensis has simple, smooth-margined, heart shaped leaves that can grow 7” long. In spring they emerge burgundy-bronze, eventually maturing to emerald green, and finally turning yellow in fall. Particularly noted for its fragrant, late summer flowering period, the tiny, white-aging-to-creamy-buff flowers bloom on branched conical panicles to 8” long at the tips of new stems. The flower buds only open very slightly retaining a rounded pearl-shape appearance described by the common name of pearl-bloom.          P. sinensis should be sited where the flowers can be easily seen and sniffed. Flowers are monoecious, requiring no more than one plant to produce capsules containing multiple seeds. Photo credit: R. Armstrong

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Mexican anise

Hidden in plain sight at the corner of the Wister Center, this tiny Illicium mexicanum is still pumping out beautiful red blooms well into October. With the bloom time extended from spring to autumn, compared to our native Illicium which blooms only in spring, the large, red, protruding flowers of I. mexicanum can be enjoyed alongside the plump brown seed pods throughout the growing season.

Though this particular I. mexicanum ‘Aztec Fire’ at the Scott Arboretum of Swarthmore College is maybe a foot tall, this cultivar can grow to be 8 feet tall and 6 feet wide. Also known as Mexican anise, it has a natural pyramidal growth habit, contributing to its minimal need for pruning, which can be done if needed after flowering.

Planting I. mexicanum in a protected, evenly moist but well-draining area with an abundance of organic material will ensure its survival. Although best grown in full to part shade, I. mexicanum will adapt to full sun in about three years if the soil is not too dry. The evergreen, dark, shiny, green leaves smell of anise when crushed, making them an undesirable snack for deer. Photo Credit: R. Armstrong

Calamagrostis x acutiflora ‘Karl Foerster’

Feather reed grass

I’m finding myself always drawn to this plant. Maybe it’s as far out as the collective consciousness of the world persuading my emotions. Or maybe it’s as simple as we have great gardeners here at the Scott Arboretum of Swarthmore College. Either way, this plant always looks fantastic. Calamagrostis x acutiflora ‘Karl Foerster’ is the most popular of the hybrid feather reed grasses.

‘Karl Foerster’ reportedly does well in heavy clay soils, unlike many other ornamental grasses. It loves full sun with medium-wet soil. Generally, C. x acutiflora tends to  produce fewer flowers and develop floppier foliage as shade increases in its location.

‘Karl Foerster’ aids in erosion control, flourishing on the banks of bodies of water. Since this grass stays below two-and a-half feet wide, it is a superb option for narrow spaces or mass grouping. Pinkish-purple flower spikes that emerge in May give this grass its height of five feet. It keeps these spikes far into winter; the entire plant can then be cut back before new shoots emerge providing year-long interest. Examples of Calamagrostis x acutiflora can be found throughout the Nason Garden. Photo Credit: R. Armstrong

Datura metel

Horn-of-plenty

Horticulturist Josh Coceano of The Scott Arboretum of Swarthmore College pulls out the self sown seedlings of Datura metel from the Entrance Garden each spring, leaving only a few to grow into mounds of showy, fragrant blooms.

Winter hardy to USDA Zone 9-10, it is best to purchase young plants from nurseries in spring or start your own seeds indoors eight weeks before last frost. Plant D. metel after all sign of frost has passed into a rich, humusy, well-drained area with full sun and regular moisture.

Commonly known as horn of plenty, this shrubby, tender annual will sprawl in the garden so it is best to leave three feet between plants. Also great in containers, plant D. metel in an area where the flower fragrance may be enjoyed. Harvest the ripe seeds to plant the following spring after the large white blooms are finished.

If D. metel is kept in a container, cut it back and overwinter indoors in a sunny window. This plant belongs to the nightshade family and all parts of it are extremely toxic, so take care when deciding to incorporate D. metel into your garden if there are pets or children around. Photo Credit: R. Armstrong

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Helenium autumnale ‘Salsa’

Being able to fill in gaps in the garden with a reliable, pest free, perennial is a wonderful feeling, especially when that perennial brings such a burst of color. The dense, compact  and tidy habit of Helenium autumnale ‘Salsa’ will do just that for your garden from late summer through fall. H. autumnale can be found in the Pollinator Garden at the Scott Arboretum covered with bright red blooms that will age to shades of orange and yellow as the seasons progress.

Also known as Helen’s flower, or sneezeweed, this pollinator magnet is an excellent option for planters, borders, or simply massing throughout the garden. H. autumnale grows to be 18-20 inches tall and can spread 20-24 inches wide in a well-drained, moist , sunny location. Photo Credit: R. Armstrong

Chelone lyonii ‘Hot Lips’

I’ve been watching this plant get larger and larger; noticing its dark serrated foliage in different gardens throughout the Scott Arboretum. Last week when it bloomed, I was pleased to find showy, pink, snapdragon-like flowers perched at the top of the stems. Chelone lyonii ‘Hot Lips’ is a herbaceous perennial from the family Plantaginaceae.

Also known as pink turtlehead, due to its flower resembling an open-mouthed turtle, it naturalizes in full sun to part shade in rich, moist, humusy, soil. This is a deer tolerant native which escaped gardens in parts of New England and has made its way into the forests. C. lyonii spreads slowly by rhizomes or by self seeding, however, it is not considered invasive.

There are no serious insect problems that come with this perennial, but some may be susceptible to mildew if soils are kept on the dry side with poor air circulation. If grown in too much shade, staking or pinching may be required. Examples of Chelone lyonii can be found in the Pollinator Garden and in the Scott Entrance Garden. Photo Credit: R. Armstrong

Liriope muscari  ‘Monroe’s White’

Liriope has been in almost every garden where I have worked. I keep waiting for the day that I get sick of seeing it, but that day has not yet come. It’s a fantastic ground cover that keeps gardens looking full and orderly. This fast growing, easy care, perennial needs only occasional maintenance once established. Lilyturf benefits from removal of old foliage each spring and division every 2 to 3 years.

L. muscari is used in Asian inspired gardens along rock paths or planted in masses under trees and shrubs. The leaves of liriope were used as bookmarks in ancient China where paper was an expensive commodity. L. muscari is fantastic for cut flowers arrangements, is pet friendly, bird friendly, and has year round interest.

This particular cultivar, with its white flower spikes, can be found in the Theresa Lang Garden of Fragrance.  ‘Monroe’s White’ prefers more shade, well-drained soil, and grows slower than other lilyturf. This makes it an excellent option for specimen projects or areas where you do not want anything invasive.   Photo Credit: R. Armstrong

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Tricyrtis formosana ‘Autumn Glow’

I’ve walked past this little plant dozens of times, subconsciously waiting for it to do something special. Yes, it has an interesting shape, and the leaves are nicely variegated, but it never stood out as a plant that would do much more than provide a hardy, naturalizing groundcover. Tricyrtis formosana proved me wrong.

Perched at the top of 2’ tall stalks, striking clusters of orchid-like amethyst-purple flowers with dark spots begin blooming towards the end of July and continue to bloom into the fall. T. formosana, also commonly known as toadlily, originates from Japan.

It is best grown in Zones 6a to 9b in an evenly rich, moist, slightly acidic soil. ‘Autumn Glow’ does not perform well in deep shade and much prefers to be planted somewhere that receives a couple of hours of sun.

This massing plant will spread by rhizomes, forming healthy colonies if planted where it is happy. An example of how to use Tricyrtis formosana in the garden can be found in Isabelle Cosby Courtyard.

Several species of Tricyrtis will be available at the Scott Arboretum Selections: Fall Sale on Sept. 15 to 17 so you can try this great plant in your garden.  Photo Credit: R. Armstrong

Pycnanthemum muticum

There is always some hesitation when I think of planting mint in my garden. I’ve spent hours digging it out, trying to prevent it from completely swallowing all of my other plants.

Luckily, Pycnanthemum muticum is here to satisfy any urge for mint. With it’s silver-green foliage and pink-white flowers, mountain mint is a low maintenance, clump-forming perennial that brings, what seem to be, all of the pollinators in the area to the backyard. P. muticum is an excellent nectar and pollen source and provides a dense ground cover for wildlife. It is also deer resistant. P. muticum naturalizes in full sun to part shade in Zones 4 to 8. When planted in masses, the silver-green leaves give an appearance of being dusted with a white powder.

The leaves can be used for tea, insect repellent, or simply for ornamental purposes. Mountain mint is best left to naturalize in native plant gardens, cottage gardens or meadows but can also be root pruned with a spade in spring if naturalizing is unwanted. An example of Pycnanthemum muticum can be found outside of the Cunningham House and the Wister Center. This plant is available at the Scott Arboretum Selections: Fall Sale on September 15 to 17. Photo Credit: R. Armstrong

Viburnum rhytidophyllum ‘Cree’

I’ve always loved the texture of the leaves of leatherleaf viburnums. They never fail to remind me of some sort of reptile skin. Since it’s an evergreen shrub, I get to experience the leaves at any time of year; although, during the summer, V. rhytidophyllum has bright red fruits that eventually turn shiny black, which form after white blooms.

Viburnum rhytidophyllum ‘Cree’ is more compact with dark green leaves, which do not curl to the extent of the species, implying ‘Cree’ is hardier. Growing to be 8 feet wide and high, this slow growing viburnum requires acidic, moist, well-draining soil in full sun to part shade. Viburnum rhytidophyllum can be found behind Parish hall. Photo Credit: R.Armstrong

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Liriodendron tulipifera

While I was walking the grounds of the Scott Arboretum on a exceptionally hot day, I began to think back to my time as a teenager running around campus on balmy summer nights. The massive tulip tree towering over the Conifer Collection was always a prime destination. With the first day of summer just recently passed, I find writing about this particular tree to be more than appropriate.

Liriodendron tulipifera, able to grow to 90 feet tall with a possible span of 50 feet, holds the largest swing I have ever personally swung on. A splendid tree for large landscapes, L. tulipifera is best grown in moist, well-drained, rich soil. L. tulipifera is a deciduous tree, indigenous to North America with its name deriving from its cupped-shaped, tulip-like flowers that bloom from May to June, depending on the region. These beautiful yellow and orange flowers go relatively unnoticed until the petals begin the drop below the tree. The four-lobed bright green leaves can grow to be eight inches across and turn stunning golden yellow in autumn.  Photo Credit: R. Armstrong

Spigelia marilandica

Making my way from the swing, my next destination was the Scott Outdoor Amphitheater for some nighttime hide and seek. At the entrance of the amphitheater, nestled under some rhododendrons, are little clumps of Spigelia marilandica.

This herbaceous perennial has glossy green leaves, which highlight the trumpet-shaped, red and yellow blooms that open in June, attracting hummingbirds to the garden. Best grown in full to part shade, S. marilandica is drought tolerant, but prefers moist, rich soil. The low clumping habit of S. marilandica, commonly referred to as Indian pink, makes it a fantastic addition to wildflower gardens, native plants gardens, woodland gardens, and border fronts.

Kniphofia ‘Pineapple Popsicle’

Although I was up to some mischievous nonsense as a teenager, I always made sure to be respectful when needed. Running around and hiding in bushes was appropriate in the Crum Woods, but was not appropriate anywhere near the Cunningham House. As an adult, walking these gardens, I notice plants I never stopped to appreciate as a youngster, such as the Kniphofia ‘Pineapple Popsicle’ along the west side of the Terry Shane Teaching Garden.

This little herbaceous perennial is best grown in well-drained soil, where root rot can be a severe problem, particularly in winter. ‘Pineapple Popsicle’ is a hybrid, causing the flower to produce inviable seed. It is best to divide the rhizomes for propagation. Commonly known as red-hot poker, Kniphofia has a 1- to 2-foot yellow flower spike emerging from the center of a cluster of coarse, long, thin, leaves anywhere from June to July. The flowers bloom bottom to top changing their shape from wider on the bottom at the beginning of their bloom to wider on the top at the end. The blooms last two to three weeks and are best pruned back immediately after they are finished blooming. Photo Credit: R. Armstrong

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Phlox ‘Minnie Pearl’

This low-growing, white-flowered Phlox is an easy choice for the backbone of a garden. ‘Minnie Pearl’ is the first Phlox to bloom in the season and will slowly self-seed to mix with other perennials. Its fragrant, white, star-shaped flowers with gold eyes are excellent at attracting hummingbirds and butterflies; they are also superb cut flowers. ‘Minnie Pearl’ has proven to be very mildew resistant, impervious to wilt, and immune to bacterial spot, making this a fantastic option even after the blooms have faded and all that’s left is foliage. Although this miniature beauty was originally found accidentally by the side a the road in MIssissippi, it can now be found along Magill Walk at the Scott Arboretum.

Growing 15 to 20 inches tall, ‘Minnie Pearl’ needs to be planted in full to partial sun with well draining soil. It can form a 2-foot wide patch in 3 years, providing a crisp and clean appearance as an addition to borders and informal gardens. Under ideal conditions, this plant can live for approximately 10 years. There is occasional upkeep with Phlox; it should be cut back at the end of autumn in preparation for winter.  Photo credit: R. Armstrong

Eryngium x zabelii  ‘Big Blue’

These stunning blue beauties are as picturesque as they are prickly. From early to mid-summer in the Terry Shane Teaching Garden, Eryngium x zabelii ‘Big Blue’ will have bright violet-blue flowers atop four foot stems full of silver-green spiny foliage. Also known as Sea Holly, this herbaceous perennial has blooms that hold their color while the rest of the flowers develop, until the entire stem is full of mature blossoms. This thistle-like blossom is fantastic for cut flower arrangements, fresh or dried.

Thriving in full sun and well-drained, sandy soil, ‘Big Blue’ is resilient once established but prefers to not be disturbed. Plants can be dug up to be moved or divided if necessary, but due to their long taproot, it can be quite difficult and they will be slow to recover. Sea Holly is long-lived, hardy, withstands neglect during dry spells, and is tolerant of salt.

Eryngium x zabelii requires occasional maintenance and upkeep. It is best to cut it down in early spring before active growth; deadhead throughout the season to prevent self-seeding. Photo credit: R. Armstrong

Hydrangea macrophylla ‘Penny Mac’

The Hydrangea Collection along Whittier Place is well on its way to being in full bloom. A first to present its flowers is Hydrangea macrophylla ‘Penny Mac’. This hydrangea was named after Penny McHenry, the founder of the American Hydrangea Society. She received the plant as a gift in 1975 and spent years propagating, planting, and dispersing this hydrangea, which always seemed to bloom well in her gardens.

H.  macrophylla is one of the most common species of Hydrangea. This deciduous shrub can grow to be 4- to 6-feet high and wide. Also known as a bigleaf hydrangea, its blossom colors can vary from blue to pink depending on soil acidity. Acidic soil produces blue flowers and basic soil produces pink flowers. H.macrophylla continuously blooms from late June through August on old and new growth. ‘Penny Mac’ will reliably flower each year, and is hardy to USDA Zone 5.

Finalizing the construction near the Hydrangea Collection calls for the landscape to be restored. Along with some large trees, the established Hydrangea collection has been undamaged, offering a sense of age to the land that is sometimes more difficult to accomplish with new buildings. Photo credit: R. Armstrong

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Alcantarea imperialis ‘Volcano Mist’

What a pleasure it is to be in the presence of such mighty elegance. Tucked seamlessly into the Scott Entrance Garden  is a blooming Alcantarea imperialis ‘Volcano Mist’. These massive beauties can approach 8 feet in diameter and have up to a 3-foot tall flower stalk.

Alcantarea imperialis is part of a large family of tropical plants called Bromeliaceae, of which approximately one-third are endangered in the wild largely due to habitat loss and overharvesting for the retail market. Fortunately, some nurseries have started producing bromeliads from seeds or pups in an effort to save the family and bring it back from endangerment.

This particular A. imperialis  was bought at the 2011 Unusual Tropical and Annual Sale and was later gifted back to the Arboretum after it grew too large for the owners to care for it properly. This past winter, the cup at the center of the plant, which typically holds water, was empty. Within a few days, the beginning of a flower spike was evident. The A. imperialis was planted in the Scott Entrance Garden in the early spring and will hopefully bloom for the rest of the summer.

Unfortunately, after the A. imperialis blooms,it will slowly start to die. The Scott Arboretum has taken steps by collecting pups from the blooming plant to continue this cultivar. In ten years time, there quite possibly will be another flowering bromeliad that was collected from this one, with just as much elegance and magnificence.  Photo credit: R. Armstrong

Calycanthus floridus

Tucked in the back of a garden or planted front and center, this versatile shrub brings an array of visual splendor and diverse fragrances. Calycanthus floridus, commonly known as Carolina allspice, has a delightful strawberry-like scent to its burgundy flowers. These aromatic blossoms are scattered throughout the modest shrub at the end of its leafy branchlets, giving a peekaboo display. The mid-spring blooms are followed by brown pear-shaped seed capsules that have a spiced cinnamon scent when crushed. photo credit: R. Armstrong

Symphytum x uplandicum ‘Variegatum’

If there is one “super plant” to be had in your garden, it simply must be Symphytum. Highlighted here is a variegated Symphytum x uplandicum commonly known as Russian comfrey. With its brilliant yellow and green fuzzy leaves, light purple blooms, and clumping habits, S. x uplandicum ‘Variegatum’ brings wonderful body, color, and texture to a garden.

S. xuplandicum ‘Variegatum’ not only brings a pop of color to the garden, it also brings beneficial pollinators, such as bumblebees. It has been used as an herbal remedy since 400 B.C. in Greece, and it is still used today as a poultice to help stimulate cell growth and keep down inflamation. As if that weren’t enough, S. x uplandicum ‘Variegatum’ also serves as a fantastic mulch and compost addition. A group of S. x uplandicum ‘Variegatum’, as well as the non variegated variety, can be found in the John W. Nason Garden. Photo credit: R. Armstrong

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