Hydrangea Gardens of the World
http://www.hortensias-hydrangea.com is the website for The Shamrock Collection, the largest collection of hydrangeas in the world. It is located at Varengeville-sur-Mer, near Dieppe, Upper Normandy, France. The 5-acre hydrangea gardens contain 1,400 species, sub-species and cultivars of hydrangeas.
http://www.esveld.nl is possibly the second largest hydrangea collection in the world with approximately 400 taxa. PlantenTuin Esveld is a combination of a large nursery and a display garden on a 1-hectare site in Boskoop, Holland.
https://www.tripadvisor.ca/Attraction_Review-g946495-d1386218-Reviews-Mimurotoji_Temple-Uji_Kyoto_Prefecture_Kinki.html is a TripAdvisor website but has the best photos I can find for this excellent hydrangea garden in Japan. The Mimurotoji Temple, Uji-city, Japan, claims to have 10,000 hydrangea plants.
http://norfolkbotanicalgarden.org/ is the website of the Norfolk Botanical Garden, Virginia, USA. This 155-acre botanical garden has the largest collection of hydrangeas in North America comprising 200 cultivars from 20 species. Designated an official North American Collection by the North American Plant Collection Consortium (NAPCC).
https://heritagemuseumsandgardens.org/gardens/northamericanhydrangeagarden/ Heritage Museums and Gardens is fast becoming a major hydrangea garden in collaboration with the Cape Cod Hydrangea Society. Begun in 2010, by 2017 the collection has grown to 8 species and 164 cultivars. There are ambitious plans for new hybrid varieties of hydrangeas to be planted, grown and studied by professional experts from across the USA. Les Lutz is Director of Horticulture and Facilities management, Mal Condon is Curator of Hydrangeas.
Heritage Museums and Gardens, Cape Cod
http://hydrangeaderby.co.uk/ is the website for Britain’s largest collection of hydrangeas comprising 490 taxa from 14 species, grown on a half-hectare site in the East Midlands. Hydrangea Derby is now holder of the UK’s National Collection of Hydrangea paniculata species with 71 cultivars.
http://www.holehirdgardens.org.uk/ is the website for a former national collection of hydrangeas in the Lake District of England. When I was there in 2007, their collection comprised 400+ varieties from 14 species.
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