Cape Cod is home to many hydrangeas. The landscapes in this historic and idyllic area in southern New England are adorned with some spectacular specimens. The Cape Cod Hydrangea Society is a vibrant and generous organization that educated the region about hydrangeas, what they refer to as “the Cape’s signature flower.” The Heritage Museums and Gardens in Sandwich, Massachusetts, dedicate an impressive amount of man hours and space to hydrangeas across the property, including a display garden and test garden.
Mal Condon is the curator for hydrangeas at Heritage. He has been propagating and growing hydrangeas for 45 years. It only takes a few minutes to chat with Condon to realize that he is full of hydrangea knowledge and that his love for this crop is real. With all of the ballyhoo surrounding hydrangeas, Cape Cod is sort of a mecca for a crop that has become very valuable to the green industry.
“Hydrangeas are the No. 2 shrub behind roses, and I think they’re so popular because of the gorgeous flower,” says Condon. “Different species can have flowering shrubs and a summer full of hydrangea flowers. They are plants that home gardeners can handle very well and that they enjoy a lot. I don’t see that change. ”
At Heritage, the hydrangea show garden was the top priority. At nearly 2 acres, the show garden is a joint effort by the Cape Cod Hydrangea Society and the museum. The first planting began in 2008 and continued through 2010, with relocations and expansions in 2012, 2013 and 2014. The show garden is home to eight types of hydrangea and more than 160 varieties. It is maintained almost exclusively by society.
“The show garden is mostly made up of macrophylloons, but we also have a decent amount of paniculatas and serratas,” says Condon. “We also have a lot of legacy strains that aren’t usually commercially available. I’m trying to find some of the old arborescens varieties. ”
Sales of hydrangeas are $ 106.8 million.
according to the USDA National Agricultural
Statistics service 2019 census of horticultural specialties.
An idea takes shape
The test garden was an idea by Dr. Michael Dirr, whose selection and breeding of hydrangeas helped catapult the crop’s popularity. Dirr got to the heart of the idea during the 2015 Hydrangea conference at Heritage and before the event ended, a plan was in place to move forward. Dirr, Bailey Nurseries, Star Roses & Plants, the American Hydrangea Society, and the Cape Cod Hydrangea Society have committed a total of $ 100,000 to initiate the test garden.
“I’ve helped Heritage track down scholarships and asked people like Mark Sellew at Prides Corner, Tim Wood at Spring Meadow, Greenleaf, and others to donate plants, and everyone responded positively,” said Dirr.
The mission of the test garden is to test the latest hydrangea introductions across the species spectrum and to report on the performance, says Dirr. Condon adds that the benchmark design incorporates some “old standards”.
Hydrangeas are tested for a number of criteria including winter / bud hardiness and re-blooming ability.
The North American hydrangea test garden
Les Lutz, Director of Horticulture at Heritage, designed the test garden, which includes sun and shade conditions for the hydrangeas as well as hardscapes, water features and complementary perennials, shrubs and trees.
“Les has created a beautifully landscaped garden that is rich in horticulture and incorporated into all types of plants, not just test series with ugly signage,” says Dirr. “The occasional visitor would have to sleep in the garden and not get away with new ideas.”
The test garden opened in the summer of 2016 with the aim of becoming the most comprehensive collection of the genus in the U.S., says Condon. By June 2020, 244 hydrangeas had been evaluated, including: H. arborescens (35 plants and eight varieties); H. macrophylla (136 plants and 21 varieties);
H. paniculata (67 plants and 11 varieties); and H. serrata: (three plants and 1 variety).
In the test garden, H. macrophylla is heavily emphasized as it makes up the bulk of commercial production.
“The Macs are great – they’re always sturdy and have a great texture and variety of colors,” says Condon. “We talk a lot about the macrophylls, but Paniculatas and Arborescens are bulletproof. They are my favorites and once established they are so good for us. ”
The macrophylls are assessed for their winter / bud hardiness, their ability to re-bloom, their flower density, their flower quality, their general growth and size characteristics, their sun tolerance and their pest and disease pressure.
In the test garden, a lot of emphasis is placed on the ability to bloom again, as the market strongly emphasizes this property. All stem tips are pinched in July – an action Condon calls the “Most Critical Test” – to assess the number of new inflorescences that develop through late August and into September.
The test garden is located in USDA hardiness zone 6a while the rest of cape is 7a. Soil preparation is a critical step in gardens, where the soils are an Ice Age marine composition with veins of stone, sand and clay, says Condon.
“We mix locally produced compost with our inherent glaciated soil. In worse cases, we check the latter to remove the sometimes larger debris, ”he explains.
Pruning is done in two stages in late winter and early spring.
The hydrangea test garden at Heritage was designed to inspire visitors with hardscapes, water features, and other shrubs and perennials.
Photo by Michael Dirr
“Aging sticks are first removed for regenerative pruning in March and early April. All of the living wood is left until the detail cut in May, when the fancy top log is removed, ”he says. “This seasonal approach to cutting has preserved a very high proportion of vital wood and at the same time maximized the development of the flower buds.”
Plants are not treated with insecticides or fungicides in the soil.
The Condon crew apply a controlled release fertilizer of just 3 to 4 ounces per established plant for all hydrangea species in the spring. The typical NPK formulation is 14-3-17, he says.
All plants receive surface / drip irrigation. The garden installs emitter rings around each plant and “links them together to create effective zone loops for absolute control of the volume of water applied and the frequency of use,” explains Condon. “It has become our practice to install irrigation within a few days of completing a planting project. Overall, this irrigation approach has had a very positive effect on plant vitality, growth uniformity and the reduction in leaf spots. ”
It comes down to helping breeders and breeders analyze this genus in order to select the best performer and perfect new strains, says Condon.
In 2020, H. macrophylla Summer Crush was named the best performer in the test garden.
“Summer Crush has great pigmentation, and highly pigmented flowers are all the rage these days,” says Condon.
All test plants are watered and each plant is pruned in late winter and early spring.
Photo by Michael Dirr
In 2020 the test garden grew by about 30% and is now almost 3 hectares. A group of volunteers nicknamed Diggermen put in more than 300 hours, including the irrigation work.
“It was surprising what we could do and I’m very happy with the extension,” says Condon.
In August 2020, a gentle opening took place in Heritage – with numerous security protocols.
For more: heritagemuseumsandgardens.org
Looking for the perfect H. macrophylla
Mal Condon says if growers could produce the ideal macrophylla for today’s market needs, it would be no larger than 3 feet by 3 feet at maturity, with stiff stems and short internodal spacing. It would be hardy with excellent stem / bud survival for good blush in summer and further growth blush in fall.