Mycorrhizal fungi directly contribute to faster plant growth and development with increased nutrient and water availability.
Photo courtesy of Mycorrhizal Applications
1 | What is the role of mycorrhizae in plant nutrition?
Outside the root, mycorrhizal fungi develop into the soil by extending their mycelium (hyphal network) and prospecting for nutrients far from the plant. The nutrients are relocated and delivered to the root. They are exchanged with the host plant through dedicated exchange structures. In this trade, the plant obtains mainly water, macronutrients and micronutrients from the mycorrhizal fungi. In return the fungal symbiont receives organic carbon compounds (photosynthates), in the form of lipids and sugars produced by its photosynthetic host. These photosynthates are then transferred and used in the growing margins of the mycelium and developing reproductive structures such as carpophores and spores.
The main outcome of this complex and finely tuned symbiotic interaction, and ultimately the role that mycorrhizae play, is to greatly improve the ability of the plants to gather and utilize water and nutrients, from the surrounding soil or substrate.
2 | Why should growers consider using mycorrhizal fungi to improve plant nutrition?
LC: This mycorrhizal symbiosis directly contributes to plant nutrient availability and utilization throughout the plant’s entire life cycle. Mycorrhizal fungi are capable of accessing nutrient pools in the soil/substrate that are inaccessible to plant’s roots by solubilizing these tightly-bound nutrients and delivering them to the plant. Due to this increased nutrient efficiency, mycorrhized plants need significantly lower amounts of readily-available fertilizers compared to non-mycorrhized ones, which reduces the economic impact of plant nutrition on the overall costs of plant production.
3 | How does mycorrhizal inoculation affect different types of plants?
LC: Mycorrhizal fungi adapted and evolved to interact with different plant species over more than 400 million years. In doing so they differentiated in specific and particular types of mycorrhizae, among which the most important are the Endomycorrhizae or Arbuscular mycorrhizal fungi (AMF), which interact with many flowering ornamentals, vegetables and farm crops, and the Ectomycorrhizae, which interact mainly with hardwoods and conifers. The most efficient mycorrhizal inocula (such as the MycoApply® professional brand produced by Mycorrhizal Applications) have different fungal species either of Endo- and/or Ectomycorrhizal fungi, capable of interacting simultaneously with multiple plants also belonging to different species. This diversity improves the plants’ environmental conditions, giving them an advantage.
More specifically, mycorrhized plants present faster growth and better resistance to stresses compared to non-mycorrhized ones. This might be the critical factor for a successful establishment of plants in a new environment, such as a production container, and for faster and improved plant production in controlled conditions.
4 | What do growers need to know about applying mycorrhizae?
LC: Although mycorrhizal interactions improve plants’ nutrient availability and utilization and reduces the toxic effects of certain nutrients’ excesses, the presence of high concentrations of phosphorous (P) is known to be detrimental for the establishment of mycorrhizae. Therefore, over-fertilization might hamper the capability of the plant to benefit from a mycorrhizal inoculum. Another key factor to establish mycorrhizae is to carefully apply the inoculum as close to the plant’s growing roots as possible, to facilitate the contact with the active ingredient (mycorrhizal fungi) and speed up the development of the symbiotic interaction.
5 | Aside from plant nutrition, are there other unforeseen benefits of mycorrhizal inoculation?
LC: Several studies and field trials have shown that plants’ resistance to abiotic stresses (including drought, salinity, pH, and heavy metals) is greatly increased. Another indirect beneficial effect of mycorrhizae that has been documented in the scientific literature is an improved ability of the plant’s defense mechanisms to be less impacted by pest attacks. This increase in immune response is considered more of an indirect benefit, and may be attributed to the increased overall vitality of mycorrhized plants in general.
Growers have a lot of variables and worries in their work. Their growing media shouldn’t be one of them. Frederic Gagnon, Lambert Peat Moss agronomist, tells us how Lambert develops consistent mixes that the company’s customers trust.
1 | Why is consistency a prime objective for Lambert?
When you have consistency in the mix, you will make the life of the grower a lot easier. It will help a lot if you receive a mix that will drain and react the same each time. A new crop will require almost the same watering and fertilization frequency because of the drainage of the mix, air space and porosity. You have enough to adjust with the weather each year. You don’t really want to deal with the mix on top of that. You can rely on this component and concentrate your efforts to adjust the other components that change from season to season.
2 | How does Lambert keep its mixes consistent?
If you can have standard processes to prepare the field and harvest the raw product, that will help you at the second step, screening. Our screening system permits almost endless possibilities. We can achieve almost every peat grade that could be asked for by the customer and we can replicate it each time. That flexibility is very important. For the customer, it’s important to receive a mix that will have the same physical properties from batch to batch, season after season.
After you screen the peat and produce your mix, it’s important to have good quality control at the end. We apply vigorous processes to ensure that all specifications are met before allowing production to be transferred to the transportation department for delivery. In any case, if one specification is not met, production will be on hold and not allowed to leave our yard. When you let the product go, you are responsible and you have to make sure the customer receives a product in total compliance with the specification they expect.
3 | What are some examples of quality control measures Lambert has taken?
Consider the EcoPeat series of mixes, one of Lambert’s newer products. It’s made with a natural fiber from the peat bog used to produce mixes with an exceptional ratio of air porosity and water holding capacity. We took many years to test EcoPeat Mixes (EPM), so when we released them and started marketing them, we were really comfortable with that product. Now, it’s a really good seller for us. The consistency of the components is the key of that mix line. At the beginning it was not so easy to always have the same grade. We needed to make a lot of adjustments. But when you can achieve exactly the same grade from batch to batch, whether it’s -25 degrees outside or +25 degrees, you are very proud of it.
We always take the necessary time to make the adjustments and test it before putting a new product on the market. We have growers willing to do a half-acre or a couple tables in the greenhouse with a new suggestion we bring to them and trial it in “real life” conditions.
4 | How do you handle growers who have different needs?
We receive a lot of requests for fine-tuning options. It’s not always a big difference, but when you can make an adjustment to help the customer to get exactly what they’re looking for, whether it’s lower pH or a mix with no N-P-K, customers really appreciate that.
Most nursery growers for example are working with EPM-40, the High Porosity Mix. It’s perlite-free and includes Canadian sphagnum peat moss and EcoPeat. It’s ideal for large containers, perennials and nursery crops.
The same principles also apply for germination mixes. You need good seed contact between the peat moss and the seed, but you also need air space. You cannot afford to have big sticks or big chunks in the mix because they will not fill the trays correctly. But at the same time, you also do not want only fines. You have to make the adjustments to make sure you have a mix that allows good seed contact and at the same time will not clog the machinery, or clog cells in the trays. Consistency is important whether you sell a truckload or just a couple pallets because every customer is important.
Perennials are a profitable crop. And to keep those sales up, Josiah Raymer, general manager at Emerald Coast Growers, advises how make a few production adjustments to keep your perennial crops looking their best.
1 | When should I pot perennial liners to overwinter for next year?
Early fall is a great time to pot liners to start bulking up for spring sales. This works well for perennial plants such as Phlox and Astilbe and ornamental grasses such as Pennisetum and Miscanthus.
If you’re wanting early spring sales of warm-weather grasses, you’ll need to perform some well-timed bulking. Grasses such as Miscanthus, Panicum, Andropogon and Schizachyrium will respond well to bulking in summer and fall months. Put up liners in early to mid-summer, allowing enough time to finish by fall. June to July is a good window. Then, let them get a good dormancy period over the winter, which promotes good vigor coming out of dormancy.
2 | Do I plant different perennials at different times?
Be careful not to pot up day-length sensitive plants too late. The shortening days and cooler temperatures trigger dormancy. Remember, tender perennials don’t bulk and overwinter well.
One way to control crops with a strong photoperiod response is by getting them potted early enough in the summer that they will be finished by September or early October. Crops with a weaker photoperiod response, such as perennial grasses Pennisetum and Miscanthus, can be potted later in summer, as they will continue to grow for an additional four to eight weeks depending on day length and temperature.
If you have potting schedules or other constraints that force you to do all of your potting at once, changing your liner size can also help control finish times. Starting with a larger liner can shorten finish times and get your crops finished on time.
3 | Should I overwinter my plants in cold frames or outside?
Either will work. Use a perennial cloth to provide protection from frigid winter in northern climates. Farther south you may be able to get away with placing plants pot tight for protection. If you’re using cold frames, be sure to vent on warmer days, or plants may overheat.
4 | How do I adjust my fertility program for overwintering?
You want to cut back as you’re nearing the dormancy period. The most flexible option is liquid feeding, but you can also schedule a slow-release fertilizer that will run out as fall begins. Choose a fertilizer with lower nitrogen as you’re moving toward dormancy — remember you want to encourage a shift from lush new growth to energy storage in the roots.
As you near the end of overwintering, and before your crops come out of dormancy, it’s important to get pH and electrical conductivity (EC) readings. You may need an application of liquid feed fertilizer, or you may need to leach your pots if your EC is low or high respectively.
5 | How do I prepare my leftover pots for overwintering?
Start by removing old foliage just before winter, but after plants go dormant. The less organic matter to deal with in spring, the better, and you won’t have to work through new growth to cut back old foliage. Both perennials and ornamental grasses can overwinter next to new production.
If plants aren’t root bound, fertilize them when they break dormancy in the spring to have them ready for early sales. If they are root bound, shift material into a larger size in the fall or the spring. Base your decision to shift them in the fall or wait until spring on whether they have enough time to root out in their new pots prior to dormancy.
A preventive fungicide drench can help reduce root rot issues in areas with wet winters.
Research indicates that shrubs in mixed containers have piqued the interest of consumers. Alec Charais, marketing and communications manager at Bailey, describes how growers can create some dynamic, big-ticket products that will boost profits for both the producer and the retailer.
1 | What makes using shrubs in decorative containers appealing for the end consumer, and what should a grower know before implementing a production program that incorporates them in the mix?
When it comes to container gardening and gardening in general, people are looking for plants that are an extension of their own personal style. For some it is a more traditional look, whereas others are trending toward more modern styling. Container gardening offers that ability to customize the experience from the get-go. Growers and retailers have the opportunity to inspire consumers with ready-made containers that feature more than just typical herbaceous plants. Our own research has told us that people are open to using shrubs in containers, yet it isn’t top of mind when in store due to lack of inspiration. Finally, shrubs in containers are easier to take care of, making them more appealing from that aspect.
2 | Are there certain varieties that work best, and what should someone keep in mind when creating a combination recipe?
The beautiful thing about it is that really, anything can work. Certainly, there are some items that are more desirable than others. Flowering shrubs with a long bloom period and compact habit such as BloomStruck® or Summer Crush® from Endless Summer® Hydrangeas make for excellent candidates because they look great as monocultures or in combination with other annual and perennial color. Foliage shrubs such as Little Devil™ Ninebark and Straight Talk™ Privet are also excellent choices due to their clean lines and almost architectural look. Southern plants such as Distylium (Vintage Jade, Coppertone™, etc.) and Gardenia (Double Mint, Sweet Star®) varieties are also excellent choices thanks to their clean, glossy, evergreen foliage making them look great in both home and commercial applications.
3 | In terms of finishing time and the care involved during production, what are some key cultural considerations (pruning, PGRs, fertility, etc.) for growers?
There are a number of ways for growers to produce decorative containers that feature ornamental shrubs. For example, Hydrangea macrophylla forces extremely well for Mother’s Day sales by taking dormant finished product early spring and heating to force into flower within 8-10 weeks with very little in the way of growth regulators. This is especially true for growers in the Midwest and Northern parts of the country. In warmer climates, much of the planting can be done early in season so the plants can have an opportunity to set new roots before shipping. Some growers and retailers prefer to bring in finished product and then simply drop it into a decorative container or wrap for quick retail presentation, which is certainly fine, as well.
4 | What should retailers do to keep them looking good on the shelf? How about consumers once they get them home?
Like all retail products, the first rule is to sell the inventory so you don’t have to care for it long term. That said, their care is really no different and is likely easier than with annual combos since shrubs don’t require constant deadheading and nutrition. If the grower has incorporated a slow-release fertilizer in the media, then infrequent water-soluble nutrition is more than enough to supplement their requirements. The same would be said for the consumer once they have them home.
5 | From a pricing perspective, what about the cost/price/value equation? Are their price points to keep in mind?
This is where many growers get hung up. Due to the long-term nature of woody plant production as compared to bedding plants, liner selection is the most important influence on both quality and profitability. This allows flexibility for the grower to simply bring material in when they are ready for it, minimizing the amount of time caring for it. Some growers may opt to use potted liners or bare root if their facilities are set up for it, which can reduce their up-front costs provided they have the production capacity for this.
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.
H. arborescens ‘Mary Nell’
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).
Hydrangea arborescens can be found growing in Georgia’s Cloudland Canyon State Park and along North Carolina’s Blue Ridge Parkway.
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.
H. arborescens ‘Annabelle’ in Cape Cod.
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.
This H. arborescens with yellow foliage was an exciting find, but the cuttings didn’t root well and the seedlings turned out green.
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.
From the Mt. Cuba trials: ‘Ryan Gainey’ (left) and ‘Total Eclipse’ (right).
‘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.