Top photo: ‘Mt. Airy’ in flower, all photos by Michael A. Dirr
Who would have thought Fothergilla would become a mainstream nursery flowering shrub? Better question: 30 years ago, who knew anything about the two species, F. gardenii and F. major? The genus was not mentioned in my Ohio State horticulture classes (circa 1962-66). My first serious introduction occurred in the early 1970s when the late Henry Ross, owner of Gardenview Horticulture Park in Strongsville, Ohio, showed me the plants in his garden. He shared one, which I carried to the University of Illinois in Urbana, where it was planted in our garden around 1974. While teaching at the University of Illinois (1972-79), I scheduled three-day field trips in late April to early May to Cincinnati, visiting Mt. Airy, Rowe, and Spring Grove Arboreta. At Mt. Airy, a beautiful fothergilla in full flower coincided with the yearly trips. Fast forward to the late 1980s when I was verifying the Mt. Airy collections. I was given cuttings of this magnificent shrub, and named it ‘Mt. Airy.’ For 30 years it has gained a national and international reputation for superior 2-inch long, fragrant, white bottlebrush flowers; rich bluish green summer foliage, and kaleidoscopic yellow, orange and red fall color. The drivers in its commercial acceptance have been the relative ease of cutting propagation and ease of container culture.
A breakthrough
Initially, I categorized ‘Mt. Airy’ as a F. major selection, but cytological studies by Dr. Tom Ranney et al., HortScience 42:470-473 (2007), showed it to unequivocally be a hybrid between F. gardenii and F. major, now correctly F. × intermedia ‘Mt. Airy.’ It is a pentapolid (5x), the result of 4x F. gardenii × 6x F. major. I have never observed fruit/seed production on ‘Mt. Airy’ and speculate sterility due to 5x ploidy, much like sterility associated with triploids (3x).
TOP LEFT: ‘Suzanne’ fall color; TOP RIGHT: Fothergilla gardenii; BOTTOM: ‘Blue Shadow’
Mark Griffith, Jeff Beasley and I wanted to breed Fothergilla, but could never locate seeds. I queried Rich Lewandowski, who with Ron Miller, collected both species throughout the native range (more on this later). Rick told me that in his numerous experiences collecting in the wild, fruit was rarely found. Quoting Rick, “Once, at the base of Shortoff Mountain in North Carolina, we hit the jackpot and found copious amounts of fruit with viable seed.” This would have been F. major.
The logical question to pose is how to improve/integrate new traits into a genus when viable seed production is a treasure hunt. Since most of the cultivars are F. × intermedia (5x), they must have arisen in cultivation from seed collected in arboreta/botanical gardens. Rick reported earlier this year of seeing F. gardeniiand F. major wild populations, less than 20 miles apart in North Carolina, but not overlapping. In Dr. Ranney’s research, ‘Blue Shadow,’ ‘Eastern Form,’ Beaver Creek, Red Monarch, May Bouquet, ‘Mt. Airy,’ ‘Red Licorice,’ ‘Sea Spray,’ and ‘Windy City’ were F. x intermedia. ‘Appalachia,’ ‘Bill’s True Dwarf,’ ‘Blue Mist,’ ‘Harold Epstein,’ and ‘Jane Platt’ were true F. gardenii(4x). ‘Arkansas Beauty’ and Mystic Harbor were true F. major (6x).
So, where are the diploids (2x)? In Ranney’s study there were none, but subsequent collections by Lewandowski et al. showed diploid (2x) F. gardenii occurred and were “geographically aligned with the southern Gulf Coast and there were absolutely no tetraploid (4x) populations until the Georgia-South Carolina border in Effingham County, Ga.” A diploid F. gardenii collected in Baldwin County, Ala., and named ‘Redneck Nation’ was given to me by Bobby Green, of Fairhope, Ala. The leaves are blue-green, soft-pubescent, turning orange-red in autumn. Container-grown plants show good vigor, density, and pretty foliage color. Heat tolerance should be high, but I do not know northern limits. I have grown all the 4x F. gardenii clones listed above and none are superior to this diploid form (2x). Tetraploid plants are theoretically more adaptable than diploids, but not so in this situation. Incidentally, a photo of ‘Redneck Nation’ reflected a 4-foot by 4-foot plant at Bobby’s nursery in Fairhope. It was growing in full sun.
