Rhododendron ‘Milestone’ – rhododendron

The Harry Wood Garden is a cove of striking pinks and deep greens at the moment, and nestled between the dense foliage, the Rhododendron ‘Milestone’ glows. Its delicate pink flowers, one strong puff from disaster, have clung to these branches through willpower and a lightning strike of potentially favorable environments. You might be thinking, Don’t rhododendrons bloom in the spring? And you would be right. This late-blooming, rusty Rhododendron does typically bloom in the spring, from early-May to mid June. ‘Milestone’ is not an exception. However, sometimes rhododendrons will bloom in the fall due to a number of uncontrollable factors: a timely rainstorm after a drought, highly stressful conditions, or in certain areas of the world, La Niña. 

Rhododendrons have long been prized as ornamental shrubs. Dubbed “the tree of roses” in Greek, over 1000 wild species populate the planet with their spring blooms, and hundreds more cultivars occupy gardens around the globe. Most cultivated rhododendrons are hybrids, having cross-pollinated and left their species names behind. Its petals have been used to make tea, its leaves for essential oils, and its fine-grained wood for a number of tools and furniture. Weston Nursery developed Rhododendron ‘Milestone’ to withstand the northeastern climates of Massachusetts, making this cultivar particularly hardy to colder zones.

Lindera angustifolia – willow-leaved spicebush

Perched atop the Biostream, this Lindera angustifolia holds on to its shining fall color like a cozy autumn bonfire. Amidst the rusting reds and souring yellows, these bell pepper orange leaves could truly embody a burning bush. The fall color won’t last much longer as the shades shift to a dusty brown, but the leaves themselves might cling to the branches through the winter months and into the spring. L. angustifolia may change colors, but it doesn’t quite lose its coat. The leaves themselves are year-round fun, with their oblong, lanceolate shape and their glossy, vibrant texture. Place this plant in a spot of your garden that could use a little autumnal pop of color.

If you’re looking to plant your own L. angustifolia, this plant has a multi-stemmed, bushy habit with plenty of texture and an aroma in the summer spiced just enough to deter deer predation. L. angustifolia can also scale fellow trees and buildings, which could add some character to your garden. This plant is adaptable to most gardens but prefers sandy, moist spots in the sun. The North American native Lindera benzoin doesn’t have quite the shock of showy color or leaf shape of its Asiatic counterpart, but it does have delightful flowers decorating its early spring branches that resemble Hamamelis blooms. 

Hamamelis virginiana ‘Harvest Moon’ – common witchhazel

We may have passed the Harvest Moon (October 6, 2025), but it’s never too late to celebrate the Hamamelis virginiana ‘Harvest Moon’. This common witchhazel gets its cultivar name from its late-blooming flowers, showing off its spooky splendor when little else is blooming this close to winter. Hamamelis virginiana consistently takes the prize as one of the last native plants to flower in the northeastern United States.

The genus name Hamamelis refers to the flowers and fruit appearing on the tree at the same time (Hama meaning “same” and melon coming from the Greek word for fruit), which is especially true for fall-blooming Hamamelis species. The life-cycle of these fruits are quite unique. The pollinated ovary enters a resting state during the winter and only begins fertilization in the spring, five to seven months after pollination. The fruit reaches maturity over the course of the summer into small green capsule dries and splits, rocketing the seeds like a cannon in late October. Just in time for the new flowers to appear! The seeds then lay dormant for two winters before sprouting.

One fall semester of college, I took a field biology class which involved tree identification. By the time we were quizzed on any of the plants, we all had to get really good at bark identification except when it came to common witchhazel. In the spring and summer months, this understory tree is delightful if unassuming, but its bizarre flowers have always been an autumnal, woodland gift. Older botanical references claim this tree is wind pollinated, but in actuality, these flowers are siren songs for moths, bees, flies, beetles, parasitic wasps, leafhoppers, and a number of other desperate critters looking for a late-season snack. In particular, you can find winter moths like witchhazel dagger moths (Acronicta hamamelis) and their larvae are known to feast on the sap and seeds. Its primary pollinators, though, consist mainly of flies and wasps.

‘Harvest Moon’ occupies a hidden pocket near the Glade, pinned between the Whittier Place backroad and the Science Center. While Hamamelis virginiana tolerates a range of shady conditions, the plant flowers best and grows larger in sunnier locations. Soils should be moist and well-drained, especially when establishing the young tree, preferably with slightly acidic and organically rich characteristics. This plant makes a great addition to a naturalized garden, winter garden, or rain garden, especially with a woodland focus. 

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Salix ‘Swizzlestick’ – corkscrew willow

There are plenty of ways to enjoy fall color at this time of year, but if you’re looking for a unique twist to yellow right now, Salix ‘Swizzlestick’ delivers. The last of the thin, rough leaves cling to the ends of the branches, but the leaves are merely the curling, green, serrated icing on the metaphorical cake. At this time of year, the branches themselves really pop. Ranging from highlighter yellow to pumpkin orange, the vibrant bark holds a 2b curl with ease, bending in a slight corkscrew, spiralling upwards like a ballerina in a music box. It’s unusual and, in its oddity, exciting. At the moment, this tree makes quite the statement framed by conifers in the John W. Nason Garden.

Salix has an estimated 350 species, most native to the cooler climates of North America and Eurasia. Although its origin is unclear, Salix ‘Swizzlestick’ heartily handles winters in Zones 5-8. There’s plenty of winter garden potential for mid-Atlantic green spaces, but for maximum swizzle branching, make a hard cut back in late winter every few years as the plant gets larger to encourage new growth. ‘Swizzlestick’ enjoys sunny, well-watered sites but is otherwise not too picky. It will happily tolerate high salt concentrations, moist environments, and low soil quality. Salix species are great for erosion control, and they’re often found in the wild along banks and water edges. 

The original swizzlestick tree is Quararibea turbinata, a Caribbean understory tree growing up to 18 feet tall. These plants also have a slight bend to some of their branches, but the real swizzling comes from its nodes – points on the stems where multiple branches shoot outwards like wheel spokes. These spoked sticks have allegedly been used for rum cocktails to mix ingredients.

Rhus aromatica‘ Fine Textured Compact Select A’ – Lacette™ fragrant sumac

In terms of eye-catching color, Rhus aromatica ‘Fine Textured Compact Select A’ might not be your first thought, but as the leaves have slowly eked gradients of copper reds, the shrub looks magical right now. The leaves have a fun, pastel sheen to them as the greens, rusty purples, and brick reds mottle together. This Lacette™ fragrant sumac blesses its browning bed at Dan West House. The dark, reddish-brown bark compliments the speckled leaf senescence slowly creeping up each branch, dripping scarlets and plums up the dying greens.

This Rhus aromatica also easily tolerates our environment and all its conditions. ‘Fine Textured Compact Select A’ enjoys anything from full sun to partial shade. Although usually grown on the drier side of soils, it doesn’t mind a little rain. The main issue is poor drainage where Rhus aromatica doesn’t like to soak for too long. The ‘Fine Textured Compact Select A’ is particularly noted for its drought tolerance, so definitely lean into the absence of water when established for best results. This shrub works excellently as a collection, stabilizing sloped conditions and forming a delightful, colorful mass. Its species name highlights the light, lemony scent the leaves emit when crushed, but the plant isn’t otherwise too scent-forward. 

Salvia glabrescens ‘Shi-Ho’ – Japanese woodland sage

In autumn, we’ve got colorful branches, colorful leaves, and – would you believe it? – colorful flowers, too! Salvia glabrescens ‘Shi-Ho’ fills that gap. These initially unassuming plants nestled along the shaded walkways by the northern corner of Trotter Hall are speckles of violet sprinkled amidst the green foliage. The late-blooming flowers beckon the last of the bees and butterflies with very little competition. This Salvia hails from the Japanese island of Honshu and survives over winter as a perennial in the Philadelphia region. Despite its common name Japanese woodland sage and its membership in the Lamiaceae family, the plant doesn’t have much of a scent compared to its fun-smelling brethren. True to its name however, ‘Shi-Ho’ perfectly dots woodland environments in partial shade and moderate soil conditions. 

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Miscanthus sinensis ‘Morning Light’ – maiden grass

Miscanthus sinensis ‘Morning Light’ is currently soaking up the last of the sun. Throughout the summer, this tall grass has been a personal favorite. Each proud, arching blade encourages its company to brush through its foliage, delighting in the gentle swishes under your hands. And it gets better. Now in the John W. Nason garden, the blooming panicles on the Miscanthus sinensis ‘Morning Light’ glow with their auburn beauty where they flutter above the greenery. Later, these blooms will puff into fluffy white clouds for further excitement. Growing up in the suburbs of Chicago, we would trick-or-treat in the snow with our winter gloves on. I’m a little shocked to see some flowers still hanging on this late in the season, but there’s always something blooming around here – even if it’s grass.

Maiden grass typically sheets fields in eastern Asia or, in the case of the United States, disturbed areas and roadsides. The wild type can be a fairly weedy plant that seeds vigorously. ‘Morning Light,’ first introduced by Japanese plant specialist Masato Yokoi in 1976, doesn’t produce viable seeds, containing its potential for invasiveness. These lovely grasses catch fire quickly, as well, and any brave gardener to try them should be sure to plant Miscanthus sinensis a fair distance from their house. Maiden grass grows fairly easily anywhere with sun, and it only needs to be cut back in early spring when new growth starts shooting.

Acer saccharum ‘Morton’ – Crescendo™ sugar maple

More familiarly exciting as the fall really hits your wardrobe and sinuses, the sugar maples have finally set alight. Acer saccharum [Crescendo™] ‘Morton’ is just one fiery example of this delightful species. On these trees, you can easily see the leaves changing color, from the way each leaf slowly loses its chlorophyll pigments in a gradient away from the sun. A whole palette of anthocyanins, carotenoids, and xanthophylls bleed into each branch. Nothing quite says fall like an Acer saccharum.

I’m particularly partial to this cultivar because we’re both transplants from the same area of Illinois; I once lived a spitting distance from Morton Arboretum. This cultivar was bred for its drought tolerance and heat resistance, making it perhaps more suited for the Philadelphia environment than some of its wild counterparts. Despite being grown frequently as a street tree, A. saccharum doesn’t typically fare well with compaction and pollution. It’s best suited for slightly acidic, moist soils in full sun, but it notoriously beats out competition in forested environments with its shade tolerance. The leaves have quickly fallen and blanketed the grass, though, so you’ll want to scamper up to the north side of campus if you want to catch them before only bark remains.

Camellia ‘Winter’s Star’ – camellia

I’ll admit I wasn’t quite taken with camellias, but their floppy petals and sweet, unplaceable fragrance reluctantly piqued my fancy as leaf color and bark categorize the rest of the late autumn season. Snaked with a small grass pathway, Scott Arboretum & Gardens boasts a couple Camellia plants behind Parrish Hall. The lovely pink ‘Winter’s Star’ cultivar flirts its colorful branches up against the building, daring passersby to catch their own whiff of light jasmine tones. This flowering shrub might fit best in a protected garden that can shield the plants from cold wind and too much direct sunlight. These plants also prefer soils that can get moist but drain easily and have high soil organic matter, and establish best when planted in spring rather than autumn. Camellia can be a bit fussy, but it otherwise handles our climates in the mid-Atlantic well.

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Chionanthus retusus ‘China Snow’ – Chinese fringetree

My first encounter with Chionanthus retusus happened when I was painting “Little Princess” pink with the other summer interns. The dead, pink tree and the collaterally splattered tree beside it are both Chinese fringetrees, enjoying a beautiful spreading habit but otherwise not drawing much attention during the peak summer season. These trees glisten with swaths of fragrant, white flowers in the spring. Unlike the native species C. virginicus (white fringetree), the flowers blossom at the terminal end of spring new growth and not before leaves emerge, swathing the green leaves in a white cloak. However, I wasn’t drawn to these flowers I have yet to truly appreciate but rather the charming blue fruits. Paired with the rotund, little leaves, the underside of an autumnal Chionanthis retusus feels like a sweet gift from nature. 

Chionanthus retusus ‘China Snow’ rests on the hillside behind Beardsley Hall and overlooks the quad in front of Martin Hall. Tucked beside the building and slightly above eye-level, the shade feels like a hideaway in plain sight to enjoy the comings and goings of campus life. Nestled close, the deeply ridged bark also shares its company, rough but joyfully distinct, traceable, and crackling with rivulets. Throughout the autumn, this tree might develop a gentle, fall yellow as it often does in Northern latitudes. In the spring, I hope to return for the delightful show of snowy white flowers as it often produces. The gardens burst with delicious treasures year-round.

Persicaria virginiana ‘Painter’s Palette’ – knotweed

The Arboretum Entrance Garden is riddled with mischievous jumpseed plants (Persicaria virginiana). Although native, the spritely spikes of plants tend to seed in and pop up no matter the back-bending weeding attempts. The flowers easily self-seed, and when poked, these seeds spring across the garden, alighting around the garden. P. virginiana also readily resists removal. This native perennial grows in clumps from its spreading rhizomes and develops tough root systems. Mostly sticking to shaded woodlands and moist environments, these pesky plants litter the Crum Woods walkways and offer a jubilant texture in their native spaces. However, for all their embedded and puckish nature in the gardens, the ‘Painter’s Palette’ cultivar has found a home here.

Persicaria virginiana ‘Painter’s Palette’ has all the fun characteristics of the original species with an additional sprinkle of color. The leaves contain a mottled variegation with shades of white and green bisected by a dark, maroon chevron pattern that fades throughout the summer. The spikes of petite flowers are a shock of hot pink where they spring up. In the shaded pathways snaking through the Arboretum Entrance Garden, these plants catch eyes and earn their striking cultivar name. For that reason, Persicaria virginiana ‘Painter’s Palette’ succeeds where its non-cultivated counterpart struggles to find its place in a colorfully maintained garden.

Ginkgo biloba – maidenhair tree

When it comes to Ginkgo biloba trees, what you see is pretty much what you get. Being gymnosperms, they don’t have flowers, and not being conifers, they don’t have distinct or unique cones. The leaves turn a delicious, shining yellow later in the fall, but even then, there are few cultivars bred for their carotenoids, mainly focusing instead on producing non-fruiting male trees and variable stem or leaf forms. A Korean international student asked me to point out a Ginkgo tree, knowing the trees are native to her home country. When she saw this tree, she chuckled. “Oh, those. We have those trees everywhere.” And yet they are so singularly majestic, especially at their magnitude around the arboretum. 

From street-level, the similarities to its common-name namesake Adiantum pedatum (maidenhair fern) become apparent, with its fan-like leaves finely separated by dark stems and bark. These trees are often found lining streets as they can easily withstand a wide range of soil conditions, salinity, pollution, and other urban challenges. However, there’s a catch. These dioecious trees have separate male and female plants, but you’ll only ever encounter male trees planted in urban environments. The female Ginkgo biloba trees have stinky, messy, fruit-like cones that litter the sidewalks with their acrid odor in the autumn. The seed coats on Ginkgo biloba cones stock up on butyric acid: the same chemical found in rancid butter or vomit. Yum! Right now is actually the perfect time to smell the stinky Ginkgo trees yourself. In our arboretum, you can catch a whiff from the many crushed cone carcasses on the sidewalks at the North Entrance of campus.

Ginkgo biloba is possibly a superhero in plant form. These ancient trees are known for being the last species of a tree genus that populated the planet over 150 million years ago. Originating during the Paleozoic Era, this tree species has withstood two mass extinction events. Many of the Ginkgo trees growing in Hiroshima also managed to survive a direct nuclear bombing: The leaves were singed but the trees were otherwise unscathed. Currently, the oldest living Ginkgo biloba tree is estimated to be 1400 years old, and the oldest ever recorded Ginkgo biloba is upwards of 3500 years old. These trees can also notoriously change their sex from male to female, likely allowing for greater numbers to produce more seeds and keep the gene pool active. It’s a tree adapted for anything.

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Whether you propagate them every year or the extent of your knowledge is the true crime case from the ‘40s, this week we’re doing a deep dive on dahlias. In our gardens, these warm-weather perennials leave their lingering radiance even as many of the other late summer blooming flowers have started to phone it in for fall.

Dahlia is a genus of plants native to Central America, Mexico, and Colombia now teeming with crosses and cultivars. The plant gets its name from Andreas Dahl, a Swedish botanist and student of Carl Linnaeus. When European colonizers first encountered the wild species, Dahlia pinnata consisted of only a single flower head with a scarlet ray and yellow disk. With over 20,000 recorded cultivars in its over 400 years of European horticultural significance, Dahlia is a genus where you can find a surplus of colors, shapes, and sizes. These plants fall under the Asteraceae family, and like the many other plants similarly categorized, Dahlia have capitulum, deceptive head inflorescences where each petal consists of its own floret. A bunch of florets unite to form a single, flower-looking inflorescence. Dahlia distinguishes itself by rapidly growing tall, erect stems and being a pain to cultivate.

Before Spanish conquest in the 16th century, this flower held little cultural significance for the Aztecs and other indigenous populations of the region. Some sources will attribute Dahlia to the Aztec war god Uitzilopochtli, but The American Dahlia Society has published rebuttals to these claims. 

One of the first potential identifications of Dahlia could come from the Badianus Manuscript. This text was a dusty, forgotten herbal compendium tucked into the corners of the Vatican library, originally published in 1552 but only recently rediscovered in the 1930s. Between the lapsed time and the rampant destruction of Aztec religious materials during Spanish conquest, fact-checking this document proves to be an archaeological challenge. An illustration in this compendium depicts a red flower with a yellow center and thin, spindly stems – potentially Dahlia pinnata or a similar species. The Aztecs also weren’t known for their flower gardens, mainly confining their non-agricultural blooms to Tithonia, Tagetes, Zinnia, and Cosmos species for ceremonies. Dahlia popularity took off once Europeans repeated their track record of importing warm weather plants to their colder-climate gardens and hoping for the best. And in 1963 dahlias were named Mexico’s national flower. 

In the Nahuatl language, its original name acocoxochitl literally translates to “water gullet plant,” and true to form, these plants love water. But only at certain points in their life cycle. Growing dahlias is not for the faint of heart. From seed, these plants need to start indoors for 8-10 weeks or just barely covered with topsoil outside 1-2 weeks before the last frost. Germination time ranges from 5 to 20 days, and they’ll need to each occupy their own pot. Plants can then be transplanted only once risk of frost has dissipated (recommended: 4 weeks after the last frost). You’ll need a spot in your garden with access to full-sun or afternoon sun and enriched soil, but too much nitrogen results in leggy plants. Before flowering, Dahlia only need water during very dry weather, but once the flowers bloom, the soil needs soaking at least once a week. Throughout the blooming season, deadhead your flowers to stimulate growth and prevent senescence.

You can collect the seeds for a Dahlia surprise the following summer, but to ensure you have the same cultivar, divide Dahlia tubers in the fall or the spring. You’ll need to lift the tubers once all of the foliage has died, placing them in pots with soil, and keeping them just barely moist in a cool, dry, frost-free location to wait out the winter. An easy task for anyone living in an older building! Once you’re ready for division (either in the fall or spring), break up the tubers so each division ends in a stem and has several eyes. Pot the dahlias with the eyes facing upwards, each in its own container. To begin stimulating growth again, keep the divided tubers in a warm spot with moderately damp soil, and begin fertilizing with half-strength liquid fertilizer once per week. Don’t transplant the plants until you know the plants won’t get zapped by frost. If you see new shoots, and the last frost is a forgotten memory, your plants are ready for their new summer home in the garden. 

Growing dahlias in the mid-Atlantic takes perseverance, dedication, and lots of water, but it isn’t impossible. If you’re up for the challenge and prepped with a sunny garden location, Dahlia might be the right plant for you.

In the book A Contemplation Upon Flowers: Garden Plants in Myth and Literature by Bobby J. Ward, the author states, “In the language of flowers, a single dahlia indicated good taste, but a collection noted instability, apparently referring to the difficulty of growing it in cooler European gardens.” At the risk of appearing unstable, here are three Dahlia cultivars worth exploring at the Scott Arboretum & Gardens.

Dahlia ‘Kelvin Floodlight’

Every other week, without fail, one of the Scott Associates highlights this dahlia for a floral arrangement. It’s a beacon in the garden. Even during a rare rainstorm while casually weeding through the Cut Flower Display Garden, a visitor stopped to ask me about Dahlia ‘Kelvin Floodlight’. One of the earliest blooming of the dahlias in our collection, Dahlia ‘Kelvin Floodlight’ siren-calls passerby with its massive, mesmerizing flower head from its towering stalks. Each petal meticulously strokes pale yellow like a radiant beam, casting a haunting lighthouse appearance at dawn and dusk.

Dahlia ‘Willie Willie’

Dahlia ‘Willie Willie’ tests the boundaries of the cultivation possibilities for dahlias. Where many flowers have a unified, circular appearance, ‘Willie Willie’ rejects conformity. Each petal wraps itself in a blanket of its own magenta-outlined design, forming a unique shape with each self-ensconced petal. Amidst the eclecticism of the Asteraceae family, Dahlia ‘Willie Willie’ exudes originality – if you don’t mind crouching low in the Cut Flower Display Garden to look for it. And besides. You cannot go wrong with a name like ‘Willie Willie’. 

Dahlia ‘Kelsey Sunshine’

While most of our dahlias live in the Cut Flower Display Garden, the summer interns managed to sneak up one of the unplanted few from the arboretum collection to plant up at the West Garden. Amidst the enthusiastic chaos of the tropical bed, this sweet Dahlia ‘Kelsey Sunshine’ continues to shoot out new blooms into the ether. Refusing to be wrangled into a normal configuration, the stems have curved and swerved amidst the Acalypha. Its blooms and curving stems more closely resemble the Badianus Manuscript depictions in egg yolk yellow.

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Callicarpa americana – American beautyberry

The vibrant purple berries of our Callicarpa americana have been the talk of the volunteer crews lately. They’re easy to spot from the sidewalks as you walk between Singer Hall and the John W. Nason Garden. Each outstretched branch offers bracelets of bright, violet berries. Throughout the fall, a number of bird varieties enjoy these fruit snacks, and although they’re edible for human consumption, the berries can taste bland when raw and have greater success as a jelly. Should you choose to grow your own American beautyberry plants, they are said to produce more fruits when grown near multiple Callicarpa americana plants. These perennials can also take up quite a bit of space,  and they would likely make a good selection if you’re looking for a shrub to take up a sunny or partially sunny space. Maintain your plants with cutbacks in the winter for improved form. They’re less tolerant of salty conditions but are otherwise adaptable to a fair range of moist soil conditions.

Ilex verticillata ‘Winter Gold’ – winterberry

Another very nice berry addition to the garden is the Ilex verticillata ‘Winter Gold’ in the Entrance Garden. This winterberry has already started to show off its creamsicle-colored berries that will persist through the winter months, hence the common name. For now, the drupes are nestled between leaves. However, they’ll hold down the fort through the winter. The empty branches and the cutback perennials will really give these orange eye candies their moment in the sun. As delicious as they look, Ilex fruits are poisonous to humans. 

The shrub itself dons a scruffy appearance, with dozens of stems launching from the base, each one equipped with their own exuberant branches. The plants grow fairly slowly, and with proper pruning techniques, they will likely grow into whatever shape suits your garden. However, Ilex verticillata are dioecious plants, meaning they have separate male and female plants. If you want your plant to produce fruits for the winter, either plant another male plant of the same species (including different cultivars!) or pray someone in your neighborhood has their own plant to pollinate your female ‘Winter Gold’ cultivar. Winterberry also belongs to the Aquifoliaceae family, known for holly plants (Ilex) which make up a majority of the currently nonextinct plants from this family. Pollen records for Ilex date back as far as the upper Cretaceous period over 65 million years ago. Our own James R. Frorer Holly Collection features a number of different species from the Ilex genus to explore.

Carpinus cordata – heartleaf hornbeam

Up from the Benjamin West House, past the Biostream, and towards McCabe Library, visitors likely don’t stop to admire this unassuming tree. From spring through summer, Carpinus cordata (heartleaf hornbeam) has a lovely, dense, round shape but nothing to call home about. Its shining glory, however, are the catkins. These strands dangle from the branches, at first covered in a fuzzy display of flowers. The female catkins have since pollinated, instead dangling enticing nutlets like light-green ornaments on its autumnal branches. This tree hails from the northern latitudes of eastern Asia. There it tends to grow in forests and mountain slopes, preferring the shaded understory and moist, rich soils to the tolerable full sun. Despite the common name, the leaves don’t scream “heart-shaped.” They’re comparable to other leaves from the Carpinus genus – serrated and deep green – with just the slightest cordate impression at the petiole. This tree is also quite versatile, handling a range of soil types and light availability within Zones 5-8. On campus, our two Carpinus cordata specimens are located at the slope by the Cut Flower Display Garden and on the northern end of Whittier Parking Lot.

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Metasequoia glyptostroboides ‘Jack Frost’ – dawn redwood

A long line of trees border the Cunningham Complex running parallel to Chester Road. This Metasequoia glyptostroboides ‘Jack Frost’ specimen nuzzles amidst the lineup. While driving along or booking it to class, the individual trees are easy to miss, losing their individuality to the screening effect. However, this dawn redwood is a delight. Fuzzy-looking leaf shoots cloak each limb as they gently bend downward before curving back up towards the light. At this time of year, tiny, immature green cones also speckle the branch tips. This particular M. glyptostroboides specimen’s shorter stature provides ample opportunity to explore the cones, branches, and leaves without having to strain your eyes or your neck on the Metasequoia allée. 

Dawn redwoods have recorded fossils over 50 million years old. These towering trees tend to lean on the wetter side when it comes to soil, and their foliage shines best in the full sun. Many of the Metasequoia trees at Scott Arboretum & Gardens have beautiful shredded red bark, but on this smaller tree, that distinguishable feature hasn’t developed yet. 

Vernonia ‘Summer Swan Song’ – narrowleaf ironweed

Outside McCabe Library, the Vernonia ‘Summer Swan Song’ is a shock of purple. Each inflorescence on the narrowleaf ironweed packs a firework of rich, fluorescent color. Each flower pops fractals into smaller trumpet-shaped flowers, disguised by their petal-like appearance. Compared to the other Vernonia species spotted across campus, the ‘Summer Swan Song’ variety is fairly small where its rounded, ball-like form falls gently beside the pathways leading to the library’s front steps. This native hybrid perennial prefers partial sun, with shade in the afternoon. Their water needs tend to be low maintenance, succeeding even in our sunny summer conditions, and it’s an excellent pollinator magnet in the early fall. Dozens of bees buzz happily between the flowers, and you might even see a butterfly or two. The plant also seems to be deer and rabbit resistant, likely due to the roughness of the thin leaves.

Juglans nigra – black walnut

Black walnut season has arrived. Their fruits have already started hitting the sidewalks. At Scott Arboretum & Gardens, two impressive Juglans nigra trees stretch the lawn in front of 3-5 Whittier Place. Both alike in dignity, these sun-loving trees encompass the canopy, finding cracks in each other’s sun-speckled umbrellas. The feathery leaflets allow for sunlight and to sift through to the ground level, perfect for the moist soils  J. nigra prefers. At this time of year, these leaves are also streaked with occasional yellow leaflets, signalling the start of the autumnal changes.

Black walnut trees also produce juglones, chemical compounds which are specific to their genus. Juglones can be highly toxic to other plants, especially azaleas, rhododendrons, blueberries, peonies, and solanaceous crops, making J. nigra not an ideal pairing. Juglone toxicity often strays beyond the confines of the tree’s drip line after maturity and can infiltrate a larger radius over time. Keep this chemical ecological relationship in mind when planting. 

While I’m not the leading expert on foraging, here are a few tips that could help a novice gathering black walnuts for the first time. Go ahead and carefully snag any walnuts you find, making sure that they still have the nuts inside if they’re cracked open on the ground already. Next, you’ll want to hull, or clean, your walnuts to get at the nuts inside. Don’t worry about fancy tools, just smash them with your feet and harvest the hardened nuts from inside. Black walnuts also produce a black, inky liquid that will get all over and stain your hands dark yellow, so do wear gloves for this part. Once you have all of your foraged, cleaned nuts, let them dry in a well-ventilated area for a few weeks to release extra moisture. Then you’ll be ready to crack open your walnuts. If you don’t have a black walnut nutcracker, a hammer should do the trick, but be careful of any flying nut pieces. You might also want to soak the nuts to help loosen the shell. After separating the shells, you’ll have your own collection of foraged black walnuts to enjoy.

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Cercis chinensis ‘Don Egolf’ – Chinese redbud

Redbuds have exciting Cercis genus features. From their cordate leaves to their luminous spring flowers that cover the branches, each redbud has something to offer. Nestled between the tree peony beds, the Cercis chinensis ‘Don Egolf’ has its own unique flair. On this particular tree, the long-dead flowers have found new life as burly smatterings along the bark. Clusters of browned, senescing flowers grip the branches like gnarly bark whorls or parasitic, infested outgrowths of some kind. They add an eye-catching thrill to this lovely tree. 

Native to woodlands and thickets of southern China, this tree grows more shrubbily in our own ornamental collections. Compared to our own native C. canadensis (eastern redbud), C. chinensis ‘Don Egolf’ has larger spring blooms and a shorter stature. The Chinese redbud’s leaves have a glossier shine, but the fall color tends to be less exciting, peaking at a wilting yellow-brown before dropping. This particular cultivar is notably sterile, and doesn’t produce the long seedpods of the standard C. chinensis. 

Kniphofia ‘Gold Rush’ – red hot poker

When this flower first began blooming in the Cut Flower Display Garden behind the Wister Center, I wasn’t even convinced it was a flower or an inflorescence. Instead, its tubular-shaped blooms emulate tiny, cartoonish conifers. These drooping flowers open their petals in midsummer when other flowers might be looking scorched or tired, and they offer a unique point of interest for any flower fan.

This cultivar ‘Gold Rush’ isn’t your typical red hot poker. For one, it’s not red. In our gardens, Kniphofia ‘Gold Rush’ has greener and yellower hues than many of the genus originating in South Africa. This cultivar is also tested for winter hardiness down to Zone 6, and could likely withstand harsher winters given the proper mulching and protection. In most cases, these flowers want full-sun, but tucked under one of our magnolias, these pokers come back happily each summer. 

Malus x scheideckeri ‘Red Jade’ – flowering crabapple

One of the final trees standing from the previous crabapple collection, this unassuming Malus x scheideckeri ‘Red Jade’ brings hints of the coming fall even early in September. Its delightful red fruits sprinkle amidst its multicolor leaves, already in the process of shifting to an autumnal mindset. Where other trees in the area display giant leaves or coniferous shade, this tree has a vibrant glow in an unsuspecting pocket of the Arboretum. Between the Cunningham parking lot and the tennis courts, one might not expect much in the way of tree collections, but this gem brings excitement and pizzazz through its color and unwieldy habit.

This particular crabapple is a hybrid of M. floribunda (Japanese flowering crabapple), and M. prunifolia (Chinese crabapple). Hybridization across species is common in crabapples, and it can be difficult to identify the naturalized species outside of ornamental environments. For this particular cross, the leaves have slightly serrated margins, and the trees produce delicate, white flowers in the spring. The ‘Red Jade’ cultivar weeps its branches, creating a low umbrella, excellent for catching as much of the full sun as it can.

They’re also notoriously disease-ridden. Among the major issues is fireblight. This disease wrecks Malus plants across the genus, hindering apple production across the country. In the spring, once the temperature breaks 65°F, the fireblight bacterium can infect a tree, typically entering through damaged and wounded parts of the tree, and kill entire blossoms, fruits, shoots, and branches in the process. Unfortunately, these diseases also love the warmth and humidity of this region, and the bacteria easily spreads with rainfall. These trees also suffer from scab, powdery mildew, and leaf spot on occasion. In general, prune this tree during the late winter months, not the spring, to reduce likelihood of acquiring a disease.  

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Summer Intern Zoe James demonstrates how to dig and divide irises and hostas.

Tune into the Gardener’s Almanac to learn what we are doing in the garden at this moment. Learn from Scott Arboretum staff which plants we are pruning, planting, weeding and which pests we are monitoring and removing right now. This virtual almanac is a great reference guide for gardeners.

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The newest emerging disease affecting shade trees, Beech Leaf Disease, is spreading across the Northeastern states and it is on campus. This disease affects American beech, European beech, and Oriental beech. It is currently having a devastating effect on the predominant beech/birch/maple forest in New York state and has been present in Massachusetts since 2020.

Symptoms include leaf striping, curling, and leathery texture. These symptoms can be observed from May to October by looking up into the canopy. Microscopic worms, known as nematodes, feed on plant foliage, affecting the leaf tissue and photosynthetic process, which in turn weakens the tree. As the disease progresses, leaf and bud production is impacted along with heavy leaf loss. A single tree can have heavily infected branches and unaffected branches. 

The beech genus, Fagus, lacks any natural defenses to this disease. The two options for treatment are foliar sprays and trunk injections. Foliar sprays are typically for young specimens while mature, large specimens require a trunk injection. Many homeowners are choosing to protect their large, mature specimens with these treatments. 

Here at Scott, we are proactively treating approximately 30 specimen trees in the heart of campus, where we are seeing little to no symptoms at this time. 

Unfortunately, our predominantly maple/beech forest along the Crum Creek is extensively affected. We are letting nature take its course in the woods and are developing plans to replant the beech-dominated areas with native trees. We plan to use a selection of white oaks (Quercus alba), hickories (Carya spp.), and maples (Acer rubrum), and also allow our tulip poplars (Liriodendron tulipifera) to seed in. In the understory, we are planting redbud (Cercis sp.), chokeberry (Aronia sp.), and native dogwood (Cornus florida). 

Learn more about this disease in Pennsylvania here. 

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