Hydrangeas
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40 free Hydrangeas trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Hydrangeas are some of the most recognisable shrubs in any garden, with flowerheads the size of dinner plates and colours that can shift from one summer to the next. Behind the familiar blooms is a plant with a surprisingly eventful past, carried between continents by plant hunters and woven into ceremonies, place names and local legends. This quiz gathers the fun facts people most often go looking for: what decides whether a bush blooms blue or pink, what the showy parts of the flower really are, how the different kinds climb, spread and survive, and where the plant's various names came from. It also follows hydrangeas out of the garden and into medicine, drinks, travel and a few places you would never expect to find a shrub. It is written for gardeners, flower lovers, teachers and anyone building a nature round for trivia night. Every answer comes with a short explanation, so you will leave with a handful of facts worth repeating over the garden fence.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Hydrangea flowers that turn blue or pink depending on the soil act as a natural version of what?
A pH indicator
A pH indicator in plant form: blooms come blue at a reading of about 5.5 or lower, pink at 6.5 or higher, and purple in between.
Q 02The name hydrangea comes from Greek words that liken the plant's tiny seed capsules to what?
Water vessel
Water vessel joins the Greek hydor and angeion, a grand name for seed capsules only a few millimetres across.
Q 03The big colourful 'petals' of a mophead hydrangea are not true petals at all but which flower part?
Sepals
Sepals do the showing off on large sterile florets, while the hydrangea's fertile flowers are tiny and tucked out of sight.
Q 04Every part of a hydrangea is mildly poisonous if eaten because the plant holds compounds that release which toxin?
Cyanide
Cyanide is bound up in the plant's cyanogenic glycosides, yet hydrangeas are reportedly sometimes smoked as an intoxicant despite the danger.
Q 05In Japan, a herbal tea brewed from hydrangea leaves is poured over small statues each April to mark whose birthday?
The Buddha
The Buddha is bathed in the tea every April 8, a stand-in for the nectar that nine dragons poured over him at birth in legend.
Q 06Which US state named the oakleaf hydrangea, a native shrub of southeastern woodlands, as its official state wildflower?
Alabama
Alabama chose it in 1999, honouring a shrub named for lobed leaves that turn red, bronze and purple in autumn.
Q 07Masses of summer hydrangeas earned Faial the nickname 'Blue Island' in which mid-Atlantic archipelago?
The Azores
The Azores have adopted the shrub as an unofficial emblem and plant it along roadsides, although it was introduced and has turned invasive.
Q 08Soil treatments cannot change the flower colour of hydrangeas that bloom in which colour?
White
White hydrangeas make no pigment for soil chemistry to act on, so they stay white wherever they are planted.
Q 09In Japan, hydrangeas in full bloom are the classic emblem of which stretch of the year?
The rainy season
The rainy season falls in June, when apprentice geisha may wear seasonal hair ornaments of willow or, less often, blue hydrangea.
Q 10The hydrangea 'Runaway Bride Snow White' was named Plant of the Year for 2018 at which British flower show?
Chelsea
Chelsea gave its top new-plant prize to a hybrid bred in Japan, the homeland of the familiar bigleaf garden hydrangea.
Q 11Which metal must a bigleaf hydrangea absorb from acidic soil before its pink flowers can turn blue?
Aluminium
Aluminium reaches the roots only in acidic soil; alkaline soil locks the metal away, which is why the same shrub then flowers pink.
Q 12Gardeners who want pink rather than blue hydrangea flowers often dig in which material to make acidic soil alkaline?
Lime
Lime makes the ground more alkaline and so denies the roots the metal that blues the flowers, a trick that does nothing for oakleaf hydrangeas.
Q 13Which alternative name for the mophead hydrangea doubles as the Latin form of a French woman's given name?
Hortensia
Hortensia echoes the name Hortense, but no real Hortense has been pinned down, and the Larousse dictionary suspects the Latin word for garden instead.
Q 21Cherokee healers, and settlers after them, used the root of smooth hydrangea to treat which painful complaint?
Kidney stones
Kidney stones and bladder stones were the target, and hydrangea root is still listed in herbal references as a possible diuretic.
Q 22The hydrangea sphinx, whose larvae feed on wild hydrangea in eastern North American wetlands, is which kind of insect?
A moth
A moth of the sphinx family Sphingidae, it also raises its young on buttonbush, another shrub of damp ground.
Q 23Hydrangea febrifuga, one of the fifty fundamental herbs of Chinese medicine, was long used against which disease?
Malaria
Malaria is fought by its alkaloid febrifugine, and a synthetic cousin of that compound is now used in veterinary medicine.
Q 14A French naturalist tried to name the hydrangea after Nicole-Reine Lepaute, who helped predict the return of what?
Halley's Comet
Halley's Comet arrived in March 1759, one month before the date she and two colleagues had computed; an asteroid and a lunar crater now bear her name.
Q 15Naturalist Philipp Franz von Siebold named a hydrangea after his partner Taki while posted to which Japanese port city?
Nagasaki
Nagasaki, where he served at the Dutch trading post of Dejima, now counts the hydrangea as its official city flower.
Q 16Gramado and Canela lie in a tourist district called the Region of the Hydrangeas in which South American country?
Brazil
Brazil promotes the district to draw visitors to the hills of Rio Grande do Sul, where some locals still speak a German dialect.
Q 17HMS Hydrangea, launched in 1940, was one of the Royal Navy's flower-named convoy escorts built as which type of warship?
Corvette
Corvette was a title the Royal Navy revived for these U-boat hunters, whose design was borrowed from a whale-catcher.
Q 18Wild bigleaf hydrangeas carry flat flowerheads of tiny central flowers ringed by showy ones, a form known as what?
Lacecap
Lacecap is the natural form; breeders later packed the whole head with showy florets to create the ball-shaped kinds that dominate gardens.
Q 19Climbing hydrangea scales tree trunks, rock faces and shady house walls by gripping with which structures?
Aerial rootlets
Aerial rootlets sprout along its stems, though they grip less firmly than those of some wall-climbers, so gardeners often add ties.
Q 20Which nickname did smooth hydrangea earn because its stem bark peels away in several thin layers of different colours?
Sevenbark
Sevenbark it is; the shrub grows wild across the eastern United States and spreads by creeping stems to form colonies.
Q 24Amacha, a Japanese drink brewed from fermented hydrangea leaves, has a name that translates into English as what?
Sweet tea
Sweet tea earns the name from phyllodulcin, a compound in the leaves that is hundreds of times sweeter than table sugar.
Q 25Meigetsu-in, a Zen temple nicknamed the Temple of Hydrangeas for its June display, stands in which Japanese city?
Kamakura
Kamakura doubles up: its Hase-dera temple is also famous for a Hydrangea Path that blooms in June and July.
Q 26Ajisai, the Japanese word for hydrangea, is also the name of which mirror-covered object launched by Japan in 1986?
A satellite
A satellite shaped like a hollow sphere, it carries 318 mirrors that flash sunlight back to Earth so surveyors can fix positions precisely.
Q 27The hydrangea family also includes which fragrant garden shrub, known to botanists as Philadelphus?
Mock orange
Mock orange is a cousin of the hydrangeas, named because its blossom looks like that of citrus trees and smells of orange flowers and jasmine.
Q 28Botanists place the hydrangea family in the order Cornales alongside which better-known group of flowering trees?
Dogwoods
Dogwoods give the order its name through their genus Cornus, and the tupelo trees of American swamps belong to it too.
Q 29Most wild hydrangeas grow in East Asia, yet botanists first described the genus from plants in which American colony?
Virginia
Virginia supplied the first described plants of a genus that runs to roughly a hundred species and ranges across Asia and the Americas.
Q 30Bigleaf hydrangeas pruned hard in spring often fail to bloom that summer because their flower buds sit on which stems?
Last year's growth
Last year's growth carries the buds, which gardeners call blooming on old wood; reblooming varieties flower again later on new shoots.