Bloom Watch: The Azalea Collection

Bloom season for the Azalea collection is fast approaching, and Curator of the Arboretum’s National Native Azalea Collection Carson Ellis is keeping an eye on the plants as they begin to blossom. Read on for her weekly updates on what’s blooming in the garden.

---

At the tailend of our native azalea bloom season, visitors can still enjoy scattered flowers from Rhododendron prunifolium in the landscape (but don’t dally, this is your last chance for azalea flowers until 2024!). While the azaleas fade, the Eurybia macrophylla and E. divaricata (pictured left) are starting to bloom. The  basal foliage for these two asters can be seen growing prolifically throughout the landscape, but they seem to be blooming most where our restorative tree work has brought a little more sunlight to the forest floor.

Towards the back of the landscape, visitors might notice that we have completed the re-decking and installation of improved handrails for a second bridge. From this bridge you can enjoy a peek into the Azalea Collection’s small natural wetland, where jewelweed (Impatiens capensis) and lobelias (Lobelia puberula; pictured right) are in bloom. As a final wildflower note, now is the time to look carefully at our pathway edges for the cryptic but fantastic flowers of the cranefly orchid, Tipularia discolor. These diminutive, moth-pollinated orchids are numerous in the Azalea Collection landscape but can be difficult to spot because they bear their delicate flowers and their purple-spotted leaves in separate seasons. 

In the past week, the Rhododendron prunifolium have continued to lure visitors into the Azalea Collection with their fiery hues, but within the Collection delicate white flowers have been the theme. R. prunifolium is joined by a R. serrulatum (pictured left) specimen, currently well-spangled with sweet-scented, star-like flowers. In a fun example of what it’s like to be the Azalea Curator, though, this specimen would have recently been considered, by some authorities, to be R. viscosum. R. viscosum has an extensive range accompanied by variable habitats, bloom times, and morphology, all of which has led to the complex sometimes being lumped into one species (R. viscosum) and sometimes split into multiple, including R. serrulatum, R. coryi, and R. oblongifolium. Katherine Kron’s 1987 assessment favored lumping and would have called our specimen R. viscosum. Recently, though, R. serrulatum was again recognized as a species in Weakley’s 2018 “Flora of the southern and mid-Atlantic states”. The two are distinguished by differences in habitat and morphology, including presence of pubescence on the interior of the R. viscosum corolla tube, while that of R. serrulatum is glabrous. Having learned from my work with azaleas to be mistrustful, I split open a flower to be certain: glabrous and, for now, Rhododendron serrulatum.

In addition to R. serrulatum, a few other white flowers can be enjoyed in the Collection this month, including Goodyera pubsecens, one of our native orchid species, Cephalanthus occidentalis, Monarda clinopodia, and Silene stellata (pictured right). These species are scattered through the landscape, none blooming in great masses– plan a scavenger hunt for yourself and see if you can find them all!

---

---

In the past week, the Gregory Bald hybrid azaleas have begun to fade, leaving only a few scattered Rhododendron viscosum specimens in flower. We still have Rhododendron arborescens and Rhododendron prunifolium to look forward to in the Collection, but this month many Rhododendron aficionados take to higher elevations in search of blooms. Recent trips to Hoopers Bald, Elk Knob, and Gregory Bald (pictured left) were fruitful grounds for this budding Native Azalea Curator’s search for inspiration and the finest flowers. This week I also look forward to co-leading a trip to Roan Mountain, in collaboration with the Arboretum’s Adult Education department, for further exploration of the natural spectacles that make our mountains, and our native azaleas, so special.

Back in the Collection, though, the Rhododendron maximum is starting to bloom along with several understory flowers of note. Guests have been curious about the tall, yellow-flowered Carolina lupine (Thermopsis villosa; pictured right) which has been blooming near the Collection’s entrance. While Thermopsis villosa, like many of the herbaceous perennials in the Azalea Collection, would grow 5’ tall, or taller, volunteers on the Azalea Crew and I have taken care to give these robust species a good “Chelsea chop” to encourage lower, branching growth. The phrase “Chelsea chop” suggests that this activity should coincide with London’s annual Chelsea Flower Show, in late May, but I chop all June long and sometimes twice-over. Also blooming near the Collection entrance is a single specimen of (one of my favorites) Spigelia marilandica. While readily available in the nursery trade, this woodland species is uncommon across much of its native range and listed as critically imperiled in the state of North Carolina. Over-harvest of its roots, which are used in traditional medicine to expel worms and treat migraines, may be one reason for its decline in the wild. Lastly, the graceful Asclepias exaltata can be found blooming across the path from the Rhododendron cumberlandense. Gardeners might recognize this genus– Asclepias denotes the milkweeds, host plants for the caterpillars of monarch butterflies!

---

Earlier in the year I found a large cocoon in a spicebush and curiously clipped it out. It rode along in my cup holder, back and forth between the Azalea Collection, all spring. Yesterday a magnificent Hyalophora cecropia moth (pictured left), the largest native moth in North America emerged! This has little to do with azaleas except, perhaps, that we can expect these moths to take wing around the same time that the Rhododendron cumberlandense (which the moth obligingly posed on) are in bloom. And that, like our native azaleas, Hyalophora cercropia are members of our local forest ecosystem. While the adult moth lives only for a couple weeks and never eats, its offspring, as caterpillars, will feed on the leaves of several trees that can be found in the overstory of the Azalea Collection, including birches, cherries, and dogwoods– a reminder that gardening for ecology requires diverse plantings!

In azalea news, the lightly fragrant R. eastmanii (pictured right), a rare species endemic to South Carolina, recently began to bloom just past the first wooden bridge. Down the trail from the R eastmanii, more of the hybrids collected from Gregory Bald have begun to bloom, as well, sporting rich near-red hues. When planning your visit, be aware that the trails in the Azalea Collection will be closed past the first wooden bridge on Sunday mornings until August 7th– this is in support of a long-term migratory bird study by the Wild Bird Research Group. Specimens of R. cumberlandense and R. viscosum can still be observed blooming in the first half of the landscape, though!

---

---

In May, we have been enjoying some stunning R. calendulaceum (pictured left) which can be found peppered throughout the Collection. Highly variable, with colors ranging from creamy yellows to luminous reds, this is the species that inspired Bartram to write in his 1791 book, Travels: “… the clusters of blossoms cover the shrub in such incredible profusion on the hillsides, that suddenly opening into view from dark shades, we are alarmed with the apprehension of the hill being set on fire.” R. calendulaceum and R. arborescens (which is also putting on a few early blooms in the Collection) are the two azaleas species which naturally occur on the Arboretum’s property and can be also found growing along Bent Creek Rd and Running Cedar Road.

Also in bloom are the R. colemanii (pictured right), the “newest” of the azalea species, which was officially recognized in 2008. At one time R. colemanii was confused with R. alabamense, though differences in morphology, range, and flowering phenology inspired further investigation. Flow cytometry then revealed that R. colemanii is a tetraploid while R. alabamense is a diploid (ploidy numbers refer to the number of chromosome sets that an organism carries in its cells) confirming that the two are separate species. You never know when a new species might be hiding in plain sight and genetic research has kept azalea taxonomy exciting!

While the flowers of Rhododendron canescens, R. periclymenoides, and R. vaseyi, are fading out, a few R. austrinum, R. flammeum, and R. atlanticum can still be enjoyed in the Collection. They are joined by R. calendulaceum (pictured left), which has been blooming for the past week alongside Bent Creek Road, but has just begun to flower inside the Collection. One specimen of R. arborescens  (pictured left) is also showing its first flowers– while fragrance is not typical in R. calendulaceum, the scent of R. arborescens is a delight and something to look forward to. In the back of the Collection, the Gregory Bald hybrids are beginning to break bud, making them the last of our specimens to leaf out. 

Mayapples (Podophyllum peltatum; pictured left) are now blooming and New York ferns (Amauropelta noveboracensis) continue to unfurl in the understory. New York ferns can be confused with hay-scented ferns (Dennstaidtia punctilobula), which are common in similar habitats and have a similar appearance. A fun device to remember the difference is that “New Yorkers burn the candle at both ends”– if the fern frond tapers strongly at both the tip and the base, it is likely a New York fern, and not hay-scented.

---

After a week in Georgia attending the Azalea Society of America and American Rhododendron Society annual joint convention, I was excited to return to Asheville this week and check in on the Azalea Collection. Just in time for our Native Azalea Day celebration this Saturday (April 29th), more azalea species have begun to bloom! Though the Rhododendron canescens are mostly past their peak, the impressive R. austrinum and R. periclymenoides are hanging in there, along with several specimens of R. vaseyi scattered throughout the Collection. Under the high canopy of several venerable white oaks, a grouping of R. flammeum hybrids from Georgia’s Flint River bring together a nice range of color on the hillside, along with other interesting hybrids, like R. canescens ‘Eco Morris Red’ (pictured right). I was most excited, though, to visit with our R. atlanticum (pictured left) which is now in peak bloom. While numerous species of azalea are fragrant, with some offering sweeter or more potent aromas than others, it’s my opinion that the R. atlanticum blooming now is the azalea most worth sniffing this week– don’t miss it!

While the azaleas are rightfully stealing the show, don’t forget to look for wildflowers like the purple-flowered wild geraniums, star chickweed, and doghobble, which continue to provide a charming accompaniment. And keep these plants in mind as you enjoy the garden, too– we ask that visitors don’t step off the established trails, since doing so can damage these delicate plants of the understory!

---

The Azalea Collection is starting to shine with bright new leaves and generous boughs of azalea flowers in white, pink, and orange. Since my last writing, R. periclymenoides, R. austrinum, and R. vaseyi (pictured left) have begun to bloom, attracting an array of buzzy and fluttery pollinators (and visitors, like our Grounds Crew, who popped by this week to check in on the blooms!). Last week I observed tiger swallowtail, skipper, and cloudless sulphur butterflies nectaring, along with bumblebees, hummingbird moths, one actual hummingbird, Bombyliidae flies, and several species of small, solitary bees. Spend some time near an azalea and see how many floral visitors you can observe!

Also worth looking for are the lovely blooms of Trillium rugelii (pictured right), the southern nodding trillium. While the old adage “leaves of three, leave it be” will serve you well on our trails, the three leaf-like bracts at the top of a trillium’s scape will need to be gently lifted to get a peek at this plant’s pendulous flower.

Near the Azalea Collection’s entrance (and along Bent Creek Road), walkers can also observe the unique flowers of a coralroot orchid (Corallorhiza wisteriana). Coralroot orchids are mycotrophic, meaning that instead of photosynthesizing they spend nearly all of their lives underground where they parasitize mycorrhizal fungi. Only fleetingly do they make themselves known by sending up petite flowers, thought to be pollinated by gnats and mosquitoes. 

---

Azalea flowers started opening in earnest late last week, with R. canescens among the first to bloom, soon to be joined by displays from R. vaseyi, R. austrinum, and R. periclymenoides. Alongside them, silverbells (Halesia tetraptera, pictured left), pawpaws (Asimina triloba), and the Florida anise tree (Illicium floridanum, pictured right) are also in bloom.

The Illicium and Asimina both sport maroon-colored flowers with musky-fetid fragrance, flower traits associated with pollination by flies and beetles. If you’re growing Asimina at home for their unusual fruits (which some tasters will compare to bananas with a hint of strawberry, but I would counter that they taste more like banana with a hint of manure), now is a good time to make sure your stand is getting pollinated– Asimina grow in self-infertile colonies and require cross-pollination from a separate individual to produce fruits.

Also keep an eye on the forest floor for the carpet of ferns and sedges, dotted with sweet ephemeral wildflowers, which continues to flush out. I noticed this week that scattered foamflowers (Tiarella sp) have begun to bloom throughout the Azalea Collection, alongside the bright pink flowers of violet wood-sorrel (Oxalis violacea).

---

---

The recent cold snap has slowed the onset of spring, but scattered ephemerals throughout the Azalea Collection continue to bloom. Adding to the mix, I recently noticed that the white-flowered spikes of Pachysandra procumbens (Allegheny spurge; pictured left) have sprung up. These are easily observed on a frosty morning, when the foliage flops to the side. By the warmth of the afternoon, the attractive, mottled leaves of this native groundcover will right themselves again, hiding the flowers below. Look closely and you might notice that Pachysandra procumbens has monoecious flowers, meaning that the female and male parts are borne separately– inconspicuous female flowers are tucked into reddish bracts at the base of the inflorescence and male flowers are held at the top. One might expect petals to be the showiest parts of a flower, but Pachysandra procumbens has none. Instead, clusters of white stamens that draw the eye to this fragrant flower of the forest floor. 

The Arboretum is also home to several species of Hexastylis. Like the Pachysandra, these plants grow low to the ground and have flowers without petals. There are eleven species of Hexastylis known to grow in North Carolina, making our state the epicenter of Hexastylis diversity. Many of these species are visually similar and difficult to distinguish with leaves alone, making spring the best opportunity to identify them. In the Azalea Collection, Hexastylis rhombiformis (pictured right and below), the French Broad heartleaf, can be observed growing alongside Bent Creek under the shade of Kalmia latifolia and Rhododendron maximum. Look for the distinctive, heart-shaped leaves and gently move aside the leaf litter to find the vase-like flowers hidden underneath.

For those of you ready for showier floral displays, April is not far off and promises the beginning of our azalea bloom season. In the meantime, though, you can brush up on your native azaleas at a talk from Patrick Thompson, a conservation horticulturist and curator of the Davis Arboretum special collections. Patrick will be presenting on his work safeguarding the beauty and diversity of native azaleas in Alabama on March 27th at 4pm. Get more details and register here. 

---

March 8, 2023

Things are getting busy in the Azalea Collection as crews of Arboretum horticulturists, looking forward to spring, lend a hand to remove brush and resurface the trails. The forest floor is also getting busy with expanses of Erythronium umbilicatum (pictured left), now beginning to open their cheery yellow blooms throughout the collection. These charming plants, named “trout lilies” in respect to their dappled foliage, are easily confused with E. americanum, but subtle differences, like E. umbillicatum’s lack of auricles on its tepals, dimpled capsule apex, and usually lavender-brown pollen, help distinguish the two. The trout lilies are joined by Stellaria pubera, Cardamine concatenata (pictured right), and several species of Viola. 

Notably, and surprisingly, the first Rhododendron in the collection has begun to bloom! The bright, purple flowers of Rhododendron chapmanii x mucronulatum (pictured left)  can be seen breaking bud beside the creek, a full month earlier than was reported in 2022. While this rhododendron hybrid does not have any native azaleas in its parentage, it does trace its heritage to Rhododendron chapmanii, an endangered Florida endemic. It makes a lovely addition to the landscape with petite evergreen foliage and is a welcome harbinger of spring blooms to come.

---

March 2, 2023

Phenology studies the cyclical events of an ecosystem. In a landscape awakening for spring, this includes the unfurling of leaves and flowers, the emergence of overwintering insects like bees and butterflies, and the spring migration of birds returning to their breeding grounds. In overwintering animals, the end of dormancy might be signaled by warm temperatures, while flowering in plants can be influenced by multiple factors, including time spent in cool temperatures, onset of warmer temperatures, and day length. 

Already I’ve observed Xylocarpa virginica, eastern carpenter bees (pictured right), in the Azalea Collection. When bees and butterflies are coaxed out of dormancy in February and March we hope that they will find adequate resources and that a hard freeze won’t follow. As gardeners, we can support spring pollinators by planting diverse gardens with early-flowering species and by leaving spent plant material, like leaves, tall grasses, and fallen wood, in the landscape to provide shelter and nesting habitat. 

In the Azalea Collection, maples (Acer rubrum; pictured left) and spicebush (Lindera benzoin; pictured right) are in bloom. While these flowers are small, they are many, coloring the canopy and understory in a fine mist of red and gold. Below, the dappled foliage of trout lilies has begun to poke through the leaf litter and diminutive Cardamine flagellifera offer up bright blooms. If you’ve ever grown cool-season crops like kale, cabbage, broccoli, or brussel sprouts, you might notice that Cardamine, with their four-petaled flowers, resemble these common crops. In fact, they do all belong to the same plant family, Brassicaceae! I imagine that these Cardamine might taste spicy like their mustard relatives, but the Azalea Collection is not for eating (wish I could tell that to the deer and

---

As the new Curator of the Arboretum’s National Native Azalea Collection, I started my work in October, just as much of the landscape was settling into dormancy; I have yet to see my first spring or summer in the Azalea Collection. Instead, I have been studying winter’s landscape: the placement of boulders on the hillside, the structure of the canopy, the tangles of Rhododendron maximumwith leaves that furl and unfurl as our days yo-yo between 70s and 20s. 

While gardens across Asheville are coming to life with daffodils, crocus, and even early cherry and magnolia trees bursting into bloom, the native plants growing in the Azalea Collection are more cautious to acknowledge February’s warm weather.

Keen eyes, though, might still spot a few early flowers: golden catkins dangling from American hazelnut (Corylus americana; pictured right) were first to unfurl, followed by the flower of Symplocarpus foetidus, the eastern skunk cabbage. Skunk cabbage (pictured right) is an unusual wetland plant, common in the northeast, but rare in Western North Carolina. Inconspicuous in color and stature, this plant can be hard to spot, but can be found along the margins of the Azalea Collection’s wetland.

Typical of the Araceae plant family, skunk cabbage have a type of flower called a spadix: small flowers borne on a fleshy stem and sheltered under the hood of a red- and green-speckled spathe. One of the earliest flowers to bloom, skunk cabbage have the curious ability to generate heat, allowing them to tolerate freezing temperatures and even melt snow. 

Already the still pools in the Azalea Collection are filled with masses of frog eggs and early butterflies, like Polygonia interrogationis, are fluttering across the sunny trails. Buds are swelling and greenery has begun to nose up through the leaf litter. Check back for updates as spring continues to unfold and be the first to know when our azaleas start to bloom!