Hydrangea arborescens

The summer of 2019 was open season on Hydrangea arborescens as I encountered/observed/studied the species in Cloudland Canyon State Park (Rising Fawn, Ga.); Cumberland Plateau (Sewanee, Tenn.), and the Blue Ridge Parkway from Oconaluftee (southern terminus), to 6,053 feet at Buck Knob, N.C., the highest elevation on the parkway where extensive colonies grow on slopes, embankments and woods edges. In Cloudland Canyon it was abundant on sandstone rock faces/steep slopes in dense shade from the top of the Canyon to the waters’ edge below, ~1,000 feet elevation change. Around the University of the South in Sewanee, it was common in limestone soils in the understory. I perpetually scout for superior flower forms and through the years discovered only two, ‘Balsam’ (‘Highland Lace’ as named by Bonnie) at ~4,000 feet in Balsam, N.C., and a spotted green and white mophead along highway 106/246 leading to Highlands, N.C. The first was propagated and freely shared and is extant in cultivation; the latter I was unable to locate again as the mowing crews reduced it to green leaves. I look for it every time we travel to Highlands. Lesson learned: if possible, collect when in the presence.

Another serendipitous discovery occurred in late April 2016 when Adrian Bloom of Bressingham Gardens in England and I were careening over mountain roads in North Carolina. A flash of yellow caught our eyes. A quick reversal and a scramble up an embankment revealed a yellow foliage lacecap H. arborescens. A gold strike, or so we thought, but the entire plant (dug up) dies, cuttings do not root and hundreds of seedlings are green. Failure? Never! Thrill of the chase.

Mt. Cuba Center (Hockessin, Del.) established a H. arborescens cultivar trial, including a mix of old and the newer Spring Meadow/Proven Winners introductions in 2018. Impressive design and excellent maintenance with three plants per cultivar; the first plant in each row pruned to about a foot and the other two unpruned. Most of the cutbacks were similar in size and stage of flower development to the unpruned on June 3, 2019. Quite unexpected as trials with H. paniculata at RHS Wisley showed that cutback delayed flowering and resulted in larger flower sizes. This is a three-year study, now in year two, with the results to be published in a bulletin and online with color photos, ratings and summations of performance. I recommend the reader access Mt. Cuba’s Baptisia publication for an idea of the quality of their work. In the cultivar descriptions, observations from the Mt. Cuba study are included.

In January 2019, I attended the IPM-ESSEN Horticulture Show in Germany, primarily to learn what is new in hydrangea, particularly I did not expect to discover anything in H. arborescens. However, three (new to me) cultivars were showcased including ‘Golden Annabelle’, Candybelle Lollipop (‘Grhyar 1407’) and Candybelle Marshmallow (‘Grhyar 1406’). Obviously, the genetics from the many pink ‘Annabelle’ types developed in the United States are being reshuffled via European breeding. I also noted Magical Pinkerbell (‘Kolpinbel’) there, which I witnessed at Cultivate in 2018. H. arborescens is well adapted to the European climate and during my 1999 sabbatical at Hillier Arboretum (Hampshire, England) and again during the 2007 International Hydrangea Conference in Ghent, Belgium, H. arborescens, especially ‘Annabelle’ was ubiquitous. Point being, there is a market in Europe for H. arborescens, although H. macrophylla and H. paniculata dominate.

From the late 1990s through 2014 at UGA and Plant Introductions, Inc. (PII), H. arborescens was bred for white and pink mophead inflorescences, compact habit, strong stems and superior foliage. The late professor Joseph C. McDaniel of the University of Illinois, who promoted ‘Annabelle’ to the world (discovered ~1910 near Anna, Ill.), told me the so-termed sterile inflorescences housed numerous fertile flowers under the showy sepals. Would seed produce mophead flowers? My technician, Vickie Waters and I collected seed in 1996/97, and produced the first mophead seedling population in 1998. Our best selection was Annabelle-01-98, which I carried to PII in 2006. It was never introduced, but it opened the floodgates for PII breeding. From almost imperceptible, pink fertile flowers in ‘Wesser Falls’ and ‘Eco Pink Puff’, via bee pollination x ‘Annabelle’, PII developed 30 mophead pinks in 2007 with the best introduced by Bailey as Bella Anna (‘PIIHA-1’). Unfortunately, production issues relegated this to the scrap heap of nursery commerce. PII continued to breed pink and white mopheads (lacecaps also) with great success but never introduced any, as there were always Achilles’ heels in the best selections. PII’s last major breakthrough was a close to red ‘Annabelle’ type with dark green foliage (February 2014) but too weak stemmed. PII was sold to Bailey in 2015 with all genetics and the company continues to develop the requisite features for strong-stemmed pink and white ‘Annabelle’ types.

Dr. Tom Ranney of North Carolina State University was ahead of UGA and PII with H. arborescens breeding and introduced eight into cultivation. I have observed/tested all and provide observations concerning performance in the cultivar section.

On July 15 and 16, 2019, I studied the H. arborescens collection at the American Hydrangea Test Garden at Heritage Museums and Gardens in Sandwich, Mass. The hydrangea garden was established in 2015 to trial newer introductions in a climate conducive to flowering success. Currently there are over 100 cultivars of H. aspera, H. macrophylla, H. arborescens, H. serrata, H. paniculata and H. quercifolia. I have traveled there each year since 2015 to conduct performance evaluations. Several H. serrata, ‘Blue Bird’ and ‘Blue Billow’, along with ‘Lady in Red’ (H. macrophylla x H. serrata) flower reliably. Each year is different, but the constant is the superiority of H. arborescens cultivars. The legacy/heirloom H. macrophylla cultivars have been a disappointment with minimal/no flowering, usually after being killed to the crowns, producing green leaves. Through those five years, only ‘Bouquet Rose’, ‘La France’, ‘Marechal Foch’, ‘Generale Vicomtesse de Vibraye’, ‘Mathilda Gutges’, and ‘Brestenburg’ showed some consistency in flowering. All the Endless Summer brand cultivars have consistently flowered since 2015 (installed in fall 2014) with Twist-n-Shout and Bloomstruck the best.

All H. arborescens were in full flower at Heritage and, ‘Annabelle’, specifically, was everywhere on Cape Cod. A few pink mophead H. arborescens were in evidence but the white mopheads dominated. For whatever reason, the pinks have not “caught on,” even where they can be successfully cultured. Mal Condon, curator of the hydrangea garden, continues to expand the collection. He is actively pursuing the older H. arborescens cultivars along with the new to develop a comprehensive gene bank and educate the public on their many attributes. Heritage will post performance results on its web site (https://heritagemuseumsandgardens.org).

Many of the cultivars of H. arborescens do not hold up well in containers. They become leggy, are thin-stemmed, inflorescences too heavy, splaying habit, and appearance rather shabby. Hydrangea arborescens show their true worth after two to three years in the ground. Many of the pink ‘Annabelle’ selections are especially prone to flop under container production because of the thin/weak stems. The pink parents, ‘Eco Pink Puff’ and ‘Wesser Falls’ have exceptionally thin, weak stems. With seasoning/age, several Invincibelle Spirit types and Incrediball Blush develop into beautiful specimens, especially in the North where day and night temperatures are cooler. At PII and in the Dirr garden (Zone 8), most pink ‘Annabelle’ types have not persisted, except Invincibelle Spirit II and it limps along. Bobby Green of Green Nursery and Landscape in Fairhope, Ala., reported that none of the known H. arborescens types (white or pink) survive under Zone 9 conditions, except for wild-collected seedlings from around Claiborne, Monroe County in Southwest Alabama, which is listed as a ghost town.

Characteristics of most of the new introductions (~20) since the 2004 publication of Hydrangeas for American Gardens (Timber Press) are presented below. I added a few old timers, like ‘Mary Nell’ which is not well known but the best of the lacecaps in my opinion. The new European introductions, with the possible exception of Magical Pinkerbell, are not yet in the U.S. and my knowledge is based on posters and literature.

Cultivars

Pink Flowers

Invincibelle Spirit I (‘NCHA1’) was the first pink H. arborescens released in 2011/dropped in 2015, superseded by Invincibelle Spirit II in 2016 which has slightly deeper sepal color and a wisp of increased stem strength. I observed sensational plants of the first in Boothbay, Maine; Chatham, Mass.; and Asheville, N.C. The plants were 3-4 feet high with 3- to 4-inch diameter pink mophead flowers in June-July. The foliage of both is smaller than the species and susceptible to leaf disease (bacterial leaf scorch). Plants in nursery containers, especially the first year, are subject to flopping. My suggestion for growers/gardeners is to create a framework of woody stems over a 2- to 3-year period. Prune lightly (tips only) to maximize foliage and carbohydrate production which results in stronger stems. Modern nursery production is predicated upon finishing a salable plant in less than 18 months from the time of planting the liner. Heavy/excessive pruning fosters more shoots, but they are thinner, weaker and when in flower guaranteed to flop. I have visited nurseries where the plants are in weeping repose and cannot be sold to retail garden center outlets.

Most nursery producers/retailers and gardeners (author included) have elevated expectations when such a transformational plant is introduced. Our penchant for the new fosters the belief/hope that the plant will equal the hyperbole/ marketing spin. I have observed the good and not so good sides of the pink ‘Annabelle’ types. They can be spectacular in the right climate, the pink to rose, almost red sepal color gradually dissipates to a lighter pink, pink-brown, finally brown.

Bella Anna (‘PIIHA-I’) has similar parentage to Invincibelle Spirit and Invincibelle Spirit II with comparable production and garden issues. To Bailey Nurseries’ credit, they pulled Bella Anna from the market after listening to their licensed growers. However, the deep pink mophead sepal color is richer than I and II and the inflorescences are densely covered by the sepals (no fertile flowers visible). At Coastal Maine Botanical Garden in Boothbay, Maine, both Invincibelle Spirit and Bella Anna have proven excellent, owing to the cooler climate. The latter is no longer available in commerce, so my discussion is moot, but points to continued problems when using the same genetics.

Invincibelle Spirit II (‘NCHA2’) was as an improvement on the original offering brighter pink sepal color, darker green foliage, stronger stems and superior container presence. It is a strong rebloomer. Estimated 3-4 feet high and as wide. The lone plant in our garden has persisted but has not been vigorous. Much of the stem strength issue with the pink types and H. arborescens in general in Zone 7 and 8 is the high night temperatures which allow respiration to break down the carbohydrates fixed via photosynthesis during the daylight hours, robbing the plant of carbohydrates does not allow for building significantly strong stems. At Mt. Cuba, side by side comparisons of I and II, clearly showed the superiority of II with its stronger stems and larger flowers. II was 5 feet high; I was 4.5 feet high.

Invincibelle Ruby (‘NCHA3’) was promoted as the first red-flowered H. arborescens. Having grown it for two years, the color is ruby-red, the center of the sepalous clusters light pink to white (silvery pink). Foliage is deep dark green and the stems somewhat stronger although the flowers weighed down the stems on the 3-gallon plant I grew. It reblooms quite actively after pruning, usually in about 8 weeks. It appears to be the best of the pink ‘Annabelle’ types for rebloom propensity. Estimated size is 2-3 feet high and wide. For richness of pink-red sepal color, this is the best of the Invincibelle introductions including the pink Incrediball Blush. At Mt. Cuba, Ruby was the slowest growing of all the pink flowered cultivars — only 2 feet high on June 3.

Invincibelle Mini Mauvette (‘NCHA7’) perished quickly in the Dirr garden but I was able to enjoy a few of the mauve-purple flowers. Habit is relatively compact, 2.5-3 feet high and wide, and stems are stronger than I, II and Ruby. It is listed as a rebloomer but mine did not persist long enough for me to know. Witnessed a few plants when on Cape Cod at retail centers. Did not impress at Mt. Cuba.

Incrediball Blush (‘NCHA4’) is larger growing, 4-5 feet high, stronger stemmed, blush pink flowered introduction. Plants I observed in flower varied from deep fuchsia when sepals were opening to softer pink later in the sequence. In the Dirr garden it has not performed well and eventually died. I rated it high at Mt. Cuba. Plants were 3 feet high and wide with strong stems.

Magical Pinkerbell (‘Kolpinbel’) (listed in RHS Plant Finder 2019) was new (to me) in 2018 where I first experienced it at Cultivate in Columbus, Ohio. The light pink mophead inflorescences were not substantial, more open with fertile flowers visible (not hidden by the sepals), borne on weak, splaying stems. The breeder is Koster in the Netherlands and I suspect the same genes were used as by Dr. Ranney and PII. According to Koster it was chosen for stem strength, able to support 8- to 10-inch diameter mophead light pink inflorescences. I look forward to testing the plant but am dubious about the credibility of the claims.

At IPM-ESSEN 2019, I uncovered several, new to me, pink Annabelle types.

Candybelle Bubblegum (‘GRHYAR1407’) is described as having large mophead flowers with striking pink color, sturdy branches, healthy green leaves with bronze hue; 4 feet 4 inches high and wide. Currently listed as Candybelle Lollipop in 2019 RHS Plant Finder. The latter may be the correct name.

Candybelle Marshmallow (‘GRHYAR1406’) produces large mophead flowers with salmon-pink color, sturdy branches, healthy green leaves, compact habit; 3 feet by 2 feet 8 inches. Photos show sepal color as light pink, closer to white.

White/Green Flowers

Mophead

‘Annabelle’ dominates the white mophead H. arborescens and possibly always will, as it is a superb plant, known worldwide and carries no extraneous monetary baggage, i.e., patent, trademark, marketing, container and tag fees like Incrediball and Wee White (emerges light pink, turning white). If a fault exists with ‘Annabelle’, it is the large perfectly symmetrical inflorescences that weigh the shoots, especially in wind and rain.

So along comes Incrediball (‘Abetwo’) claiming larger flowers, each with four times the florets of ‘Annabelle’, and stronger stems, ascending 4-5 feet high. My intuition/experience was to assign this selection to subsp. discolor because of the gray, pubescent lower leaf surface while ‘Annabelle’ is green. Although hyped as producing “massive blooms,” side by side with ’Annabelle’ there is usually not much difference. I believe the big gain is in container and garden culture where Incrediball is less floppy. At Heritage Museums and Gardens, ‘Annabelle’ and Incrediball grow side by side and the easiest way to differentiate is by lower leaf color, although Incrediball did hold the flowers more upright. ‘Annabelle’ was 5.5 feet high at Mt. Cuba.

‘Golden Annabelle’ has large white mophead flowers, green leaves with striking gold margins; 4 feet 4 inches by 3 feet 4 inches. Witnessed poster of this at IPM-ESSEN, 2019.

Invincibelle Limetta (‘NCHA8’) produces mophead inflorescences that emerge lush lime-green, lighten to greenish white, then green at maturity. Stems are stout, habit compact, 2.5-3 feet high and wide, leaves dark green. I have yet to test this. At Heritage, the habit was compact, but the flowers are white.

Invincibelle Wee White (‘NCHA5’) has proven the most sturdy- stemmed in my container and garden trials. The habit is compact, 1-2.5 feet high and wide, with strong stems supporting the symmetrical, broad-rounded mophead inflorescences. The emerging flowers are pinkish white, maturing white so the genes for pink color are part of its genetic makeup. In cutback trials it was the best white mophead H. arborescens for rebloom. Foliage is medium green, shorter and broader than the other Invincibelle introductions. I suspect Incrediball might be one of the parents. Wee White and Lime Rickey (‘SMNHALR’) maintained the cleanest foliage into November in the Dirr garden.

Lime Rickey (‘SMNHALR’) produces lime-green (more light green) mophead flowers, the sepals somewhat marbleized green-white as they age. The stamens are pink and contrast with the sepal color. Strong stems hold the flowers upright. The foliage was quite clean in the Dirr garden in 2018 and 2019. Reaches 4 -5 feet high and wide. Flowers largely as advertised except not as lime-green.

‘Ryan Gainey’ (Lil’ Annie/ ‘Greannie’) is a smaller version of the historic H. arborescens ‘Grandiflora’, 3-4 feet high and wide. The inflorescences are smaller, somewhat lumpy (not symmetrical) and certainly no improvement over ‘Annabelle’. The foliage is darker green than ‘Grandiflora’ and the stems perhaps stronger. Renamed Lil’ Annie and offered by Greenleaf Nursery in the Garden Debut brand. Fascinating that in Mt. Cuba trials the plants were 6 feet high. Plants do not read their press releases.

Seaside Serenade Bar Harbor (‘SMHAMWM’) is a compact version of ‘Annabelle’ with large white mophead inflorescences borne on sturdy stems that hold the flowers upright even in heavy rain (according to press releases). The foliage is darker green than ‘Annabelle’. Reaches 4 feet high and wide. I observed it in a 3-gallon container where it was flopping to the ground under the floral burden. With time, in the garden, the stems will become stronger. Certainly, in the retail setting it was similar to many of the large white mophead types. Not sure how much better this is than ‘Annabelle’. The inflorescence is lumpy and without grace.

Lacecap

‘Haas Halo’ is a lacecap H. arborescens with inflorescences described to 14 inches diameter. Based on my experiences, the inflorescences are larger than the species, more accurately 5-6 inches across. The stems are strong and do not bend when in flower. At Swarthmore College in Swarthmore, Pa., a large 5-feet high planting against a gray-blue stone building was quite impressive. The sepals surrounding the fertile flowers are more numerous and larger than those of the species. The cultivar is available in commerce and offers more show/pizzazz than lacecap seedlings. I consider ‘Haas Halo’ an improvement over White Dome (‘Dardom’) which has fewer showy sepals. At the time (~2009) I was testing ‘Haas Halo’, ‘Mary Nell’ arrived from Urbana, Ill. It was actually superior to ‘Haas Halo’ for flower characteristics as the sepals were larger and more numerous. Unfortunately, I lost the plant with the sale to Bailey but was able to secure a start in 2019.

‘Mary Nell’ was named after the wife of professor Joseph C. McDaniel of the University of Illinois. Although an old cultivar, it deserves use in modern gardens. It is a strong growing lacecap with a double row of sepals around the periphery of the inflorescence and thus more pronounced/showy than ‘Haas Halo’ with a single row. Inflorescences on vigorous plants are 6-8 inches across. I have grown them check to jowl and the differences are manifest. ‘Mary Nell’ is a fast grower and remarkably quick to rebloom when cut back/pruned. Leaves are large and medium green. I have watched all manner of insects enjoy the fertile flowers. The white sepals age to light green, are substantive and persist for about two months. I traced the plant back to Urbana, Ill., and a fellow gardener sent two offshoots in January 2019. By August, the number had increased to over 100 plants. Certainly, a wonderful garden plant and perhaps an even better breeding line. Easily 5 feet high forming large colonies. Thick stems as straight as arrow shafts holding the inflorescences at rigid attention. ‘Mary Nell’ was 5 feet high at Mt. Cuba.

‘Riven Lace’ is similar to ‘Green Dragon’/’Emerald Lace’ and no doubt a rename. The dark green leaves are deeply incised and somewhat cupped at the margins. The flower is a 4-5 inches diameter lacecap with a moderate number of sepals surrounding the fertile white inner flowers. Seedlings produced both normal leaves and the cut leaf characteristic. PII’s goal was to develop mophead inflorescences with the pretty cut leaf foliage. In this we failed and chucked all seedlings. ‘Riven Lace’ grows 4-5 feet high and wide and is listed as hardy to -30 degrees°F. The plants we grew were not vigorous and 3 feet high was the final destination. The three named cultivars were planted side by side in Mt. Cuba’s H. arborescens trials. When I visited in June 3, 2019 and assessed all, it was apparent there were no differences.

‘Total Eclipse’ is a lacecap type with dark green foliage growing 4-5 feet high and wide. It is a strong grower with stout shoots holding the inflorescences vertically. Offered by Millican Nursery in Chichester, N.H. Longwood Gardens (Pennsylvania) has five accessions in its collections. I have not grown this cultivar, but photos show it to be a better than the average species type. Based on the Mt. Cuba performance, the flowers are no showier than the typical inferior species type. Plants were 5.5 feet high at Mt. Cuba.

White Dome (‘Dardom’) is an older feeble lacecap type with strong stems. The flowers do not compare with ‘Haas Halo’ or ‘Mary Nell’ as sepal numbers are few and arranged irregularly around the periphery of the inflorescence. A vigorous grower, easily reaching 4-5 feet. Leaves with a gray underside reminding of subsp. discolor affinity. I believe this has been removed from the market.

Hydrangea arborescens is hardy from Zones 4 to 9. Obviously, not all cultivars are equal in terms of adaptability. Choose carefully. Flowers are formed on old and new wood. Cultivars like ‘Mary Nell’ are exceptionally fast to develop new flower buds/flowers. ‘Mary Nell’ rooted cuttings transplanted to 1-gallon containers in early June developed flower buds by mid-July. The species has much to offer including reliable flower production, year-in and year-out. There will be many more introductions in the future as its genetic potential continues to be mined.

Opinions expressed are those of the author and do not necessarily represent the views of GIE Media, Inc.