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Home , Fothergilla, Fothergilla gardenii, Fothergilla major, Gaylussacia frondosa, Kalmia cuneata, Oxydendrum

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The hybrid Fothergilla x intermedia in a US garden. Despite the age of this , it is more compact than F. major which can grow to 6m in height

HY, SINCE Fothergilla has been in cultivation Win the UK and USA for Fothergilla in over two centuries, has it achieved real popularity only in the last two decades? A number of factors have contributed to this phenomenon, and due to recent research and cultivation development, we are now ideally positioned to reflect upon the It is not only the blue-leaved of natural history and horticultural witch-alder that have caught the attention evolution of this first-rate of flowering . of gardeners recently; a long-suspected hybrid has also been confirmed. RICK DARKE History in cultivation Fothergilla belongs to the witch hazel outlines the and cultivars family, , and includes

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America and he corresponded with would take the inadvertent other early botanists exploring the hybridisation of the two species, New World flora, including Dr nearly two centuries after their Alexander Garden (1730–1791). discovery, to propel Fothergilla Garden, a Scottish physician and toward real celebrity. zoologist, settled in Charleston, South Carolina in 1752 and for more Two distinct species than twenty years devoted his spare Understanding modern fothergillas time to collecting regional flora and begins with a fresh look at the fauna, corresponding with and species’ natural histories, cultural sending specimens to John Ellis in requirements and horticultural traits. London and Linnaeus in Sweden. Though thoroughly confused in Garden is responsible for first recent garden literature, F. gardenii discovering Fothergilla, collecting and and F. major could hardly be more describing the species we now know distinct. The two species vary as F. gardenii, and introducing it to dramatically in the size of their England by 1765. The discovery and physical characters and there is no introduction of F. major is more overlap in their natural ranges. obscure; however, it was in cultivat- ion in England by the 1780s. Following a brief period of Often known as dwarf fothergilla popularity around the time of their but perhaps best called coastal introduction, both species were fothergilla, F. gardenii is restricted to sparingly cultivated through the 19th the coastal plain of North Carolina, century and for most of the 20th, South Carolina, Georgia, Alabama, though prominent horticulturists and the Florida panhandle (Sorrie et periodically attempted to draw al. 2006, Weakley 2006). attention to Fothergilla. Charles Uncommon or rare over most of its Sargent began promoting F. gardenii range, this species is found in transit- in Garden and Forest in 1895, noting ional zones from wet pine savannas that it had proved cold-hardy at the to moist -bogs properly called Rick Darke Arnold Arboretum and suggesting pocosins. Pocosins typically occupy ‘few shrubs present a more curious poorly drained ground and are fed by and beautiful effect than Fothergilla groundwater seeps. Pocosin soils only two species, F. gardenii and when it is covered in . Its tend to be deep, sandy, peaty, acidic F. major, both native to southeastern habit is excellent, too, and its foliage and nutrient deficient. The soils are North America. Although the is abundant and rich in color’ usually saturated although they are common name witch-alder is most (Sargent 1895). Richard Weaver subject to brief dry spells when often encountered in literature, it profiled the fothergillas in Arnoldia extended droughts lower water is rarely spoken: Fothergilla serves in 1971, noting that they remained tables. Fire is an essential element in equally well as botanical and undeservedly little known and that pocosin ecosystems and is important common name. there were not yet any named in maintaining the relatively open, The genus name honours Dr John horticultural varieties of either sunny conditions preferred by shrubs Fothergill (1712–1780), an English species (Weaver 1971). Michael Dirr such as F. gardenii, which is tolerant Quaker physician whose 18th-century and Harrison Flint promoted of burning as long as its are Essex garden garden included one of Fothergilla in numerous books and perennially moist. the earliest, most extensive collect- articles in the 1970s and early 1980s, Although community mixes vary ions of North American indigenous but despite such efforts, Fothergilla with moisture, shade and fire freq- . Fothergill was the patron of generally remained obscure uency, woody species often growing William Bartram’s botanical explor- curiosities, generally unappreciated, in association with F. gardenii include ations of southeastern North unavailable, and under-utilised. It Pinus serotina, Magnolia virginiana, ➤

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GENUS PROFILE Rick Darke

Acer rubrum, Chamaecyparis thyoides, Persea palustris, , cuneata, Myrica cerifera, frondosa, ligustrina, , Cyrilla racemiflora, , Viburnum nudum, and Amelanchier obovalis. Fothergilla gardenii is low-growing, typically attaining only 60–90cm in height and often suckering to equal or greater spread. The pubescent, green to blue-green are relatively small, ranging in length from 2 to 6cm and in width from 1.5 to 5cm. The bases are always symmetric and the margins are entire in the lower portion and toothed in the upper. Flowering occurs in early spring before the leaves unfold. In native habitat this is typically early to mid April. Highly Rick Darke conspicuous on still-naked branches, the 2 to 3cm tall Fothergilla gardenii ‘Blue Mist’ (top) was one of the earliest blue-leaved cultivars to be selected but it is consist of dense terminal spikes of not particularly vigorous. It exhibits the low-growing habit of the typical species (in , above) minute flowers. Fothergillas are monoecious, with male and female reduced. Only the male flowers have yellow anthers. The inflorescences flowers occurring separately within showy parts, and these are the bright are strongly and delightfully fragrant, the spikes. Petals are entirely lacking ivory-white filaments of the , with a honey-like scent that carries and even the are greatly each of which is topped by tiny far on spring breezes. Autumn colour

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F. gardenii ‘Blue Mist’ is one of the earliest named cultivars and one of the few that has always correctly been identified as F.gardenii. Introd- uced by the Morris Arboretum in Philadelphia, it remains distinctive for its glaucous blue summer foliage. The colour is not nearly as strong as F. x intermedia ‘Blue Shadow’ but it is still quite pleasing. Compact, to 80cm tall, it has low vigour and no appreciable autumn colour, but can be a valuable landscape shrub in optimum cultural conditions. F. gardenii ‘Harold Epstein’ is truly diminutive. Compact and barely 40cm tall with green summer foliage, it has better vigour and autumn colour than ‘Jane Platt’ in warmer climates . It was named for celebrated rock gardener Harold Epstein and popularised by the Arnold Arboretum. F. gardenii ‘Jane Platt’ is another older that has always been correctly identified as F.gardenii. Green-leaved and compact, to 60cm

Richard Bloom tall with lax stems, it is durable and vigorous with good autumn colour in the Pacific Northwest but much less so in warmer climates. It originated Some selections of Fothergilla gardenii show autumn colour but this species rarely exceeds 90cm in height in the Portland, Oregon, garden of varies among seedlings and with env- conditions. In warmer, drier regions Jane and John Platt. ironmental conditions, from unrem- it does better when sited in part arkable yellow-green to vibrant yellow, shade, though flowering is always apricot, burgundy and crimson. most profuse in sun. Called mountain or large fothergilla, In cultivation, F. gardenii has proved Fothergilla gardenii is the more F. major, is a highland species the less adaptable of the two species prolific seeder, producing many typically occurring at elevations of though it can be a fine performer if woody capsules typically with two 500m and above, primarily in the provided proper conditions. Though fertile seeds each. It can be propagat- mountains of North Carolina, South usually cold-hardy to USDA zone 5, ed by seed or by softwood cuttings. Carolina, Tennessee, Georgia and it is much more subject to winter Alabama, with disjunct populations damage than F. major. It absolutely Cultivars of F. gardenii in Arkansas and limited occurrence requires acidic, well-drained but F. gardenii ‘Appalachia’ is vigorous in the North Carolina Piedmont continually moist soil for vigorous yet compact, to 60cm tall with foot hills (Weakley 2006). It is growth and longevity. It is a consist- strong orange-red autumn colour. uncommon but often locally ently poor performer in heavy, F. gardenii ‘Bill’s True Dwarf’ is abundant, spreading by suckers to alkaline soils subject to drought. It among the larger selections of this form large masses. thrives in the climates of North species, growing to 1m tall, with Its mountain habitats range from America’s Pacific Northwest and blue-green summer foliage and good mature but somewhat open mesic northern Europe if provided acidic autumn colour. forests to, most commonly, ➤

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exposed ridges with thin, rocky, acidic soils and a relatively high incidence of fires. In such sites plants are often exposed to prolonged dry conditions in summer, though these are mitigated by typically cool night temperatures. At lower Piedmont elevations it prefers cliff-like, cooler north-facing slopes. Woody species occurring with F. major in mountain habitats include Pinus pungens, P. virginiana, Quercus coccinea, Q. prinus, Acer rubrum, Liriodendron tulipifera, arboreum, Halesia tetraptera, Magnolia acuminata, Magnolia fraseri, Nyssa sylvatica, and Hamamelis virginiana, which in its vegetative state is easily mistaken for Fothergilla due to its remarkably similar foliage. Fothergilla major is a large, multi- stemmed shrub capable of exceeding 6m in height. The leaves are also large – usually up to 13 cm long and 6 to 11cm wide – and the leaf bases are strongly asymmetric. The foliage is typically green and less pubescent

than that of F. gardenii. Rick Darke Plants with fully glabrous leaves Providing reliable autumn colour, Fothergilla x intermedia ‘Mount Airy’ is easy to propagate by cuttings have in the past been segregated as F. monticola, however this name is ably vivid, ranging from clear yellow in neutral to slightly alkaline soils. no longer recognised in the US, through apricot and orange to crimson Though its height in cultivation either for wild or cultivated plants and dark burgundy. Individual rarely exceeds 3m, it is still a fairly and all such material is included in shrubs often exhibit all these colours large shrub with limited utility for F. major. The name persists in the over a few sunny autumn weeks. smaller gardens. UK, as Monticola Group, but the Fothergilla major is tolerant of a Seed production in cultivation is variation seen may be just clonal wider, often more stressful range of relatively low, but this species can rather than representing a consistent conditions in its native habitats than also be propagated by softwood taxon (Bean 1988). F. gardenii and this translates into cuttings. In its native habitat, F. major much greater adaptability in cultivat- flowers later than F. gardenii, typically ion. It has greater cold hardiness, Cultivars of F. major towards the end of April, primarily often proving reliable into USDA F. major ‘Arkansas Beauty’ was due to cooler conditions at high zone 4. It grows most vigorously in introduced from a disjunct Arkansas elevations. When in cultivation well-drained organic soil but will population growing in relatively together the two species bloom tolerate heavier soils with only dry habitat. Though durable it is nearly simultaneously. moderate drainage, and though it a sparse bloomer with inferior The inflorescences are much like appreciates regular moisture it is autumn colour. those of F. gardenii but are significantly capable of withstanding considerable F. major Mystic Harbor ‘KLMG’ is a larger, with spikes up to 5cm tall. dry periods. It prefers acidic large shrub. Autumn colour is variable but is reli- conditions but performs adequately

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Fothergilla major (left), F. x intermedia (centre) and F. gardenii (right). The intermediate nature of the hybrid means that garden plants can be difficult to identify Fothergilla x intermedia number of traits. shrubs offering fragrant spring The recent horticultural renaissance The new plants filled a niche flowers, neatly attractive summer of Fothergilla can be traced to lines of previously unoccupied by Fothergilla. foliage, unsurpassed autumn colour, compact plants that began appearing Typically under 1.5m tall even after a and pleasing winter architecture. within the US nursery scene in the number of years growth, their The availability of these new late 1970s and early 1980s. Grown compact size was ideally suited for fothergillas coincided with the from open-pollinated seed obtained small residential gardens. Their increasing momentum of the native from nursery plants of F. major and adaptability to a wide range of soil plant movement in the US, which F. gardenii growing in proximity to and moisture conditions meant they encouraged gardeners and landscape one another, the seedlings were could be planted without great care architects to redirect their focus to selected for compact size, vigour, in a variety of garden settings and the diversity of the North American prolific bloom and good autumn still remain healthy and attractive. flora. Although this flora is rich with colour. Some growers continued The were even durable enough to be shrubby species, few rival the all- the lines through cutting propagation used in sweeps, masses, and for around utility of the best fothergillas. and others sold select seedlings, but hedging and enclosure, and vigorous Another turning point was Michael most of these plants were offered enough to withstand aggressive Dirr’s introduction of Fothergilla simply as F. gardenii and called dwarf pruning or periodic shearing to the ‘Mount Airy’. Here at last was a fothergilla. This identity was not ground when design imperatives named cultivar with the most questioned at the time but the plants dictated even lower height. They desirable characters of the new were clearly intermediate in a were truly, reliably, four-season compact types. Selected by Dirr ➤

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from a plant growing at Mount Airy Arboretum in Cincinnati, Ohio, ‘Mount Airy’ possessed an additional, fundamentally important trait: it was especially amenable to cuttings propagation, providing the nursery industry with a supremely marketable shrub that could be produced economically in large quantities and that presented itself well as a young container plant. Fothergilla ‘Mount Airy’ was variously offered as F. gardenii and F. major, adding to the growing debate about whether these intermediate plants might be hybrids. Decades earlier, Richard Weaver had determined that F. gardenii was a tetraploid (with 48 chromosomes) and F. major was a hexaploid (with 72 chromosomes) (Weaver 1969). He brought this up in conversation with Tom Ranney at North Carolina State University’s Mountain Horticultural Crops Research and Extension Center a few years ago and Ranney subsequently launched

a study to settle the debate. Working Rick Darke with Nathan Lynch, Paul Fantz, Paul Cappiello and other staff at the Center, the University, and Yew Dell Gardens, Ranney used flow cytometry to determine ploidy levels (chromosome number) of 17 different cultivated taxa of Fothergilla. Flow cytometry is a method of sorting cells in a stream of fluid that allows ploidy level to be determined. The results of this study (Ranney et al. 2007) are both profoundly illuminating and somewhat unsurpr- ising: the majority of commercially available cultivars are pentaploids: hybrids with 60 chromosomes. In the same article, the new hybrid species F. x intermedia is named and

described. This name can now be Rick Darke adopted for hybrid fothergillas. The inflorescences of Fothergilla x intermedia (top); in both species and the hybrid they are fragrant, Though individual testing would be appear in late spring and are composed mainly of stamens. The intensely glaucous leaves of required for absolute proof, it is F. x intermedia ‘Blue Shadow’ (above) will further excite renewed interest in the genus

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reasonable to assume that a high a plant growing at Mount Airy obscurity. The broad appeal and percentage of intermediate plants Arboretum in Ohio, it is rounded in utility of the hybrids will continue to offered commercially in recent form, growing 1.8m tall at maturity, elevate this distinctive genus in the decades as F. gardenii are actually with abundant fragrant flowers, deep world rank of ornamental shrubs. It F. x intermedia. The cultivars in this blue-green summer foliage and is hoped that continued development article are grouped according to the consistently vibrant red or orange- of this genus will result in an even conclusions of Ranney et al. (2007). red autumn colour. Although many greater range of unique and proven unnamed intermediate hybrids in selections. Cultivars of F. x intermedia commerce match it in ornamental Further introduction of plants F. x intermedia Beaver Creek characters, ‘Mount Airy’ is a certain with known provenance, and a (‘KLMtwo’). Raised by plant performer and one of the easiest to better understanding of the ecological breeder Roy Klehm, this cultivar is propagate. Paul Cappiello has context of the species, will contribute compact and rounded in form, observed that this plant is so easily to their more effective cultivation remaining under 1.2m in height after rooted in the southeastern US, the and to the roles they will play a decade of growth. Its blue-green window for taking cuttings extends in designed spaces and conserved summer foliage turns bright yellow from May into September. places. to red in autumn. F. x intermedia ‘Red Licorice’ is F. x intermedia ‘Blue Shadow’ is relatively small-leaved and low- RICK DARKE, previously Curator at without question the most dramatic growing. Selected for its dark red Longwood Gardens, Pennsylvania, new Fothergilla and perhaps one of autumn colour, it was introduced is an author, photographer, and the most promising new shrubs yet from Kentucky’s Bernheim landscape consultant. to appear in the current century. Arboretum by Paul Cappiello www.rickdarke.com Introduced and patented in the US and John Wachter. by Gary Handy of Handy Nursery F. x intermedia Red Monarch REFERENCES in Oregon, it originated as a branch (‘KLMfifteen’). Growing 2.4m tall Bean, WJ (1988) and Shrubs sport from ‘Mount Airy’. It is similar at maturity, this Roy Klehm intro- Hardy in the British Isles. 8th edition. to ‘Mount Airy’ in most characterist- duction is larger than many of the John Murray, London ics except the leaves, which emerge hybrids, with reliable deep orange- Ranney, TG, Lynch, NP, Fantz, PR green, quickly maturing to an intense red autumn colour. & Cappiello, C (2007) Clarifying and nomenclature of x powder blue that almost has to be F. intermedia ‘Sea Spray’ reaches Fothergilla (Hamamelidaceae) cultivars seen to be believed. The colour rivals 1.5m or more at maturity, and has and hybrids. HortScience 42(3): that of other glaucous plants such as summer foliage that is more blue- 470–473 pulverulenta and even Senecio green than average. The autumn Sargent, CS (1895) New or little- serpens. Although relatively easy to colour is muted. known plants. Fothergilla gardenii. from cuttings, this plant has also F. x intermedia ‘Windy City’ is a Gard. & Forest 9(402): 445–446 been tissue-cultured to meet demand recent midwestern US introduction Sorrie, BA, Gray, JB, Crutchfield, PJ (2006) The vascular flora of the more quickly. with green summer foliage and cold- longleaf pine ecosystem of Fort Bragg F. x intermedia Eastern form was hardiness into USDA zone 4. and Weymouth , North introduced to cultivation years ago Carolina. Castanea 71(2): 129–161 as F. gardenii. It is an unremarkable The future of Fothergilla Weakley, AS (2007) Flora of the example of the hybrid. The diversity and durability of Carolinas, Virginia, Georgia, and F. x intermedia May Bouquet material now available will ensure Surrounding Areas. University of (‘KLMsixteen’). Roy Klehm Fothergilla never again recedes into North Carolina Herbarium, Chapel Hill, NC. (working draft of 11 Jan selected this hybrid primarily for its ACKNOWLEDGEMENTS 2007, www.herbarium.unc.edu/ unusually abundant 5cm-tall flower flora.htm ) spikes. Autumn colour is typically Thanks to Paul Cappiello, Mike Dirr, Weaver, Jr, RE (1969) Studies in the clear yellow to apricot. Gary Handy, Roy Klehm, Rick North American genus Fothergilla F. x intermedia ‘Mount Airy’ is a Lewandowski, Dick Lighty, Bob Peet, (Hamamelidaceae). J. Arnold Arbor. benchmark against which other Tom Ranney, Bruce Sorrie and Dick 50(4): 599–619 Weaver for generously sharing their intermediate hybrids are judged. Weaver, Jr, RE (1971) The knowledge and insights on Fothergilla fothergillas. Arnoldia 31(3): 89–97 Introduced by Michael Dirr from

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