118 Fun Facts About Gardening

What is a plant that completes its whole life cycle in a single growing season called?

An annual such as the sunflower germinates, flowers, sets seed and dies within one growing season, so it must be sown afresh each year.

Which culinary herb is a biennial, growing leaves in its first year and flowering in its second?

Parsley is a biennial: it makes leaves in its first year, then flowers, sets seed and dies in its second, so cooks who want the leaves usually pull it up after one season and sow again.

Dry leaves, straw and shredded cardboard, the 'browns' of a compost heap, are rich in what?

Carbon-rich browns balance the soggy greens: grass clippings piled up on their own turn into a slimy, smelly mess, so composters mix in dry leaves or cardboard.

On a fertiliser bag's N-P-K numbers, what element is K?

Potassium takes its K from the Latin name kalium; gardeners still call it potash, after the wood ashes once soaked and boiled down in iron pots to extract it.

A soil with a pH reading below 7 is described as what?

Acidic soil, with a pH below 7, suits rhododendrons, camellias and heathers; for crops that dislike it, gardeners raise the pH by spreading ground limestone, sold as garden lime.

In acidic soil, what colour do the flowers of many hydrangeas turn?

Blue: in acidic soil aluminium becomes soluble, the hydrangea takes it up and its flowers turn blue; in alkaline soil the same plant flowers pink.

Charles Darwin's last book, published in 1881, was a study of which garden helper?

The earthworm: Darwin found his worms ignored a whistle, a bassoon and shouting, so judged them deaf, yet they shot back into their burrows when their pot stood on a piano and a note was struck.

What is the horticultural practice of removing spent flowers from a plant called?

Deadheading removes faded flowers before they set seed, so the plant redirects energy into new buds and often produces a second flush of blooms.

What is the technique of training a fruit tree flat against a wall or frame called?

Espalier was developed in Europe to coax fruit from a cool climate: branches trained flat against a sunny wall share its stored heat, and the flat shape also fits a tree into a narrow space.

The Chinese art that parallels Japanese bonsai is called what?

Penjing came first: the art of potted trees and landscapes grew up in China and was carried to Japan, where Zen Buddhism shaped it into bonsai.

Which of these shrubs is a classic choice for topiary?

Box, known as boxwood in North America, is prized for topiary because its small evergreen leaves stay dense under close shearing; yew, holly and privet are other favourites.

Seeds taken from Brazil to Kew Gardens in 1876 founded Asia's plantations of which crop?

Rubber: Henry Wickham brought some 70,000 seeds out of Brazil, and though only a few thousand sprouted at Kew, their seedlings went on to Ceylon and Malaya and broke Brazil's monopoly.

Which landscape designer perfected the French formal garden style at Versailles?

André Le Nôtre made his name at Vaux-le-Vicomte; weeks after a lavish party there in 1661, Louis XIV had its owner, Fouquet, arrested and put the same team to work on Versailles.

Keukenhof, the Dutch park planted with about 7 million bulbs a year, has a name meaning what?

Kitchen garden: in the 15th century these grounds supplied game and garden produce to the kitchens of Teylingen Castle, and the spring bulb show did not open until 1950.

The village of Giverny in Normandy is famous for the garden of which painter?

Claude Monet lived at Giverny from 1883 until his death in 1926; the water-lily pond and Japanese bridge he made there became the subject of his late Nymphéas paintings.

Why are Babylon's Hanging Gardens unique among the Seven Wonders of the Ancient World?

Their location has never been established: digs at Babylon have found no trace and Babylonian texts never mention them, so some scholars place the gardens at Nineveh instead.

Which 18th-century gardener dammed a stream to make the great lake in the park at Blenheim Palace?

Capability Brown earned his nickname by telling clients their grounds had 'capability' for improvement; Blenheim, where his lake half-drowned Vanbrugh's bridge, was one of more than 170 parks.

Gertrude Jekyll planted gardens for the houses of which architect, later the planner of New Delhi?

Edwin Lutyens was just starting out when he met Jekyll, who had turned from painting to gardens as her eyesight failed; her own house, Munstead Wood, was the first of their joint projects.

Which famous white-petalled garden flower was among Luther Burbank's 800-plus plant varieties?

The Shasta daisy took Burbank years of crossing four daisy species; a russet-skinned mutation of his first success, a potato, became the Idaho baking potato.

Monty Don took over as lead presenter of BBC's Gardeners' World in 2003, replacing whom?

Alan Titchmarsh left in 2002 after six years; his successor Monty Don was a self-taught gardener who had run a costume jewellery business until it folded.

In 1893 the US Supreme Court ruled that, for tariff purposes, the tomato was a what?

In Nix v. Hedden (1893) the court called the tomato a vegetable for tariff purposes because it is served with dinner rather than dessert, though botanically it is a berry.

The 'Three Sisters' planted by indigenous peoples of the Americas are maize, beans and what?

Squash completes the trio: the corn stalks give the beans a pole to climb, while the broad squash leaves shade the ground, keeping it moist and smothering weeds.

Dutch tulip mania's prized flame-striped petals were caused by what?

A virus streaked the petals and slowly sapped the bulbs' vigour, so Dutch collectors were paying their highest prices for diseased plants.

Apples, pears, strawberries, cherries and almonds all belong to the same botanical group as which flower?

The rose family, Rosaceae, shares more than looks: its seeds often carry amygdalin, which is why apple pips, cherry stones and bitter almonds can all release traces of cyanide.

The dahlia is the national flower of which country?

Mexico's national flower is a native: the Aztecs grew the dahlia long before the Spanish conquest carried it to Europe, and its tubers store inulin rather than starch.

Ladybirds are welcomed by gardeners because they eat what?

Aphids are the main prey of most garden ladybirds, and the larvae are voracious hunters too, which is why growers buy the beetles to release as living pest control.

The 'lady' in ladybird refers to whom?

The Virgin Mary: the beetle was 'Our Lady's bird', its red wing cases said to recall the red cloak she wears in early paintings and its seven spots her seven sorrows.

Which First Lady had a victory garden planted at the White House during World War II?

Eleanor Roosevelt got her plot despite protests from the Agriculture Department and from her husband, who reportedly wanted her told the yard was 'full of rocks'; millions of Americans planted their own.

The RHS's Great Spring Show is held each May in the grounds of which London institution?

The Royal Hospital Chelsea lent its grounds for a one-off international exhibition in 1912; the site worked so well that the RHS moved its Great Spring Show there the next year.

The Royal Horticultural Society, founded in 1804, has its flagship garden where?

Wisley, Surrey, began as one member's experimental garden for 'difficult' plants; after he died, Sir Thomas Hanbury bought it and gave it to the society in 1903.

The Svalbard Global Seed Vault sits on an island belonging to which country?

Norway paid the whole construction cost of the vault, which sits more than 100 metres inside a frozen mountain so the seeds stay frozen even if the cooling fails.

The USDA plant hardiness zones are based on what measurement?

Average annual extreme minimum temperature, in 10°F bands, defines the 13 zones; when the USDA redrew the map in 2023 with newer weather data, about half the country moved a half-zone warmer.

The daffodil is the national flower of which country?

The daffodil is worn in Wales on St David's Day, 1 March, alongside the older national emblem, the leek; Welsh-grown daffodil bulbs are also farmed for the Alzheimer's drug galantamine.

Rhubarb stalks are safe to eat, but the leaves are poisonous because they contain high levels of what?

Oxalic acid builds up mostly in the leaves, at about 0.5 per cent by weight; they are still safe on the compost heap, because the acid breaks down as they rot.

What does the French phrase behind the word dandelion mean?

Dandelion comes from the French dent-de-lion, 'lion's tooth', a reference to the jagged, toothed leaves; the older English folk name 'piss-a-bed' notes its diuretic effect.

Which lilac-flowered climber in Sierra Madre, California, is listed by Guinness as the world's largest blossoming plant?

A wisteria: bought for 75 cents in 1894, the Sierra Madre vine grew so big that it crushed the house it was planted beside, and it now sprawls across two back gardens.

The Venus flytrap is native to which part of the world?

The Carolinas in the US are its only native range: it grows wild on the coastal plain around Wilmington, North Carolina, where poaching the plants has been a felony since 2014.

Vermicompost is compost produced with the help of what?

Red wigglers are the usual species, and the finished product is sometimes called worm manure.

Clover, vetch and other legumes are grown as green manure because bacteria in their root nodules do what?

Fix nitrogen from the air: rhizobia bacteria in the nodules turn it into a form plants can use, so digging the crop in leaves nitrogen behind for whatever is grown next.

Central Park was designed in 1858 by Calvert Vaux and which landscape architect?

Frederick Law Olmsted had worked as a seaman, farmer and journalist before the more experienced Vaux invited him into the 1858 design contest, which their Greensward Plan won.

Who wrote the 1911 children's novel The Secret Garden?

Frances Hodgson Burnett drew on Great Maytham Hall in Kent, where she found an old walled garden overgrown and neglected, restored it and wrote in its gazebo.

Which writer created the garden at Sissinghurst in Kent with her husband, the diplomat Harold Nicolson?

Vita Sackville-West, barred as a woman from inheriting her family home, Knole, bought the run-down Sissinghurst in 1930; Nicolson laid out its hedged 'rooms' and she planted them.

Guinness named the Flower Dome at Singapore's Gardens by the Bay in 2015 as what?

Largest glass greenhouse in the world, and it works in reverse: the Flower Dome is cooled to 23–25°C so that olive trees and baobabs from dry climates can grow in tropical Singapore.

What do gardeners call old open-pollinated varieties, such as the Brandywine tomato, that predate modern hybrids?

Heirlooms are open-pollinated, so seed saved from this year's crop grows the same variety next year, which is how families have handed them down for generations.

The term 'guerrilla gardening' was first recorded in 1973 with Liz Christy's Green Guerrilla group in which city?

New York: Liz Christy's Green Guerillas lobbed 'seed bombs' over the fences of vacant lots, then cleared a rubbish-strewn corner at Bowery and Houston that became the city's first community garden.

Loam, the ideal garden soil, is a mix of clay, silt and what?

The proportions matter: mostly sand and silt with a smaller amount of clay, giving drainage and nutrient-holding at once.

Which group founded London's Chelsea Physic Garden in 1673 to grow medicinal plants?

The Worshipful Society of Apothecaries opened it as an outdoor classroom for apprentices; in 1722 Sir Hans Sloane secured its future by leasing them the land for £5 a year in perpetuity.

Gregor Mendel worked out the laws of inheritance by breeding which plant in his monastery's grounds?

Garden peas filled Mendel's monastery plot for eight years, yet the paper he published in 1866 was largely ignored until botanists rediscovered his laws in 1900, after his death.

The heart drug digoxin is extracted from which common garden flower?

Foxglove was a folk cure for dropsy until 1785, when the physician William Withering published 156 of his own cases to show which small doses eased a failing heart.

The sweet pea was first recorded in 1696 by Francesco Cupani, a monk and botanist working on which Mediterranean island?

Sicily: Cupani ran a botanic garden at Misilmeri and apparently sent seed to growers in England and Amsterdam; an old scented variety still carries his name.

Edwin Budding based which 1830 invention on a mill's cloth-trimming machine?

The lawn mower: Budding mounted the mill's bladed cylinder on wheels to cut grass, and the result was remarkably similar to the cylinder mowers of today.

In Beatrix Potter's tale, Peter Rabbit gets into trouble in whose garden?

Peter raids Mr. McGregor's garden in the 1902 tale, losing his jacket and shoes as he escapes; his father, Mrs. Rabbit warns, had been put in a pie by Mrs. McGregor.

The rhododendron is the national flower of which Himalayan country?

Nepal's national flower is the tree rhododendron, lali gurans, and the crimson of its blooms is the red of the national flag.

What do gardeners call the low, glass-lidded outdoor enclosure that shelters seedlings from frost?

A cold frame works as a miniature greenhouse: its lid lets the sun warm the soil and traps the heat overnight, so seedlings can be started before the normal growing season.

In horticulture, what does the branch called pomology study?

Fruit: pomology comes from the Latin pomum, 'fruit', the same root that turns up in pomegranate, literally the 'apple with many seeds'.

What is vernalization, the treatment that brings many biennials and winter cereals into flower?

Exposure to prolonged cold, a month or two near freezing for winter wheat, is the plant's proof that winter has passed, so it flowers in spring rather than in autumn.

Which Soviet agronomist coined the term, in 1928, that was later translated as 'vernalization'?

Trofim Lysenko's 'yarovizatsiya' drew wide attention and won Stalin's favour; he used that power to suppress genetics, and his critic Nikolai Vavilov died in prison in 1943.

Whose posthumous book Sylva Sylvarum reported that plants could sprout in water without soil?

Francis Bacon's book was followed in 1699 by John Woodward, who grew spearmint in several kinds of water and found it did best in the muddiest, with garden soil stirred in.

Which hydroponic method runs a thin stream of feed past bare roots?

Nutrient film technique keeps the stream so shallow, little more than a film, that the upper part of the root mat sits in air and gets the oxygen it needs.

What is the term for the pale, spindly growth of a plant raised in little or no light?

Etiolation: stems stretch towards any light and stay pale because no chlorophyll forms, an effect gardeners exploit when they force rhubarb in the dark for paler, sweeter stalks.

What do gardeners say lettuce has done when it sends up a flowering stem in hot weather?

Lettuce has bolted: it runs to flower and seed and the leaves turn bitter; spinach, onions and leeks are prone to bolting too.

Which technique raises thousands of identical plants from tiny pieces of tissue in sterile jars?

Micropropagation rests on Cornell botanist Frederick Steward's proof that cells cut from a carrot root could regrow into whole plants, the basis of modern plant tissue culture.

Which propagation technique roots a stem in damp moss while it is still attached to the parent plant?

Air layering: the stem is wounded, wrapped in damp moss and plastic, and cut free once roots have formed, a route for shrubs and trees that refuse to root from cuttings.

What does the 'F' in the seed-packet term 'F1 hybrid' stand for?

F stands for filial, so F1 is the first filial generation from crossing two inbred parents; F1 plants are uniform and vigorous, but seed saved from them gives a variable F2.

Rooting powders and gels used on cuttings are based on which class of plant hormone?

Auxin: the hormone family that makes cuttings root also kills in overdose, and synthetic auxins such as 2,4-D have been sold as weedkillers since the 1940s.

What is the yellowing of leaves, often from an iron shortage on limy soils, called?

Chlorosis is yellowing from a lack of chlorophyll; chalky soil locks iron away from the roots, which is why acid-loving plants turn yellow when grown on it.

The world's oldest horticultural society, founded in 1768, is based in which English city?

The Ancient Society of York Florists, founded in 1768, predates the Royal Horticultural Society by 36 years; its first recorded show was held in York in 1768.

What is a plant's flowering response to the length of day and night called?

Photoperiodism was uncovered by two US government scientists puzzled by a giant tobacco that grew 15 feet tall but rarely flowered in Maryland, until they shortened its days.

The hooked burrs of burdock, a garden weed, stuck to George de Mestral's dog and inspired which invention?

Velcro copies the tiny hooks that its inventor found clinging to fur and clothes after a hunting trip in the Alps. Its name blends the French words velours and crochet, velvet and hook.

Which American folk hero, a real pioneer nurseryman, planted trees across the Ohio and Indiana frontier?

Johnny Appleseed grew his trees from seed, so most bore sour apples fit only for hard cider. Writer Michael Pollan says he was really bringing the gift of alcohol to the frontier.

Which gas do plants absorb through leaf pores and build into sugars and wood?

Carbon dioxide fooled Jan Baptist van Helmont, who grew a willow for five years and decided its 74 kg gain came entirely from water. The carbon in that new wood had come from the air.

Which garden pests do gardeners trap in jars of beer sunk into the soil beside vulnerable seedlings?

Slugs that crawl in drown, yet only a few of Britain's 44-plus species eat live plants. Most feed on rotting leaves, which makes them useful recyclers in a compost heap.

Which woody grass, popular as a garden screen, includes the fastest-growing plants on Earth?

Bamboo shoots have been recorded growing 910 mm in 24 hours. Running types spread on long underground rhizomes, so gardeners have to keep them firmly in check.

Which tropical fruit, once raised at huge cost in European hothouses, was displayed at dinner parties rather than eaten?

Pineapple became a symbol of wealth because growing one in a cold climate took so much equipment and labour. A single fruit was shown off again and again until it began to rot.

Monstera deliciosa, a tropical species widely sold as a houseplant, is best known by which food-inspired nickname?

Swiss cheese plant refers to the holes that open in its mature leaves, like the eyes in Emmental. Young leaves start out whole, and botanists still debate what the gaps are for.

The glossy brown conkers that British children thread on strings for playground battles are the seeds of which tree?

Horse chestnut seeds once went to war: in the First World War, Britons, children included, gathered conkers so their starch could be fermented into acetone for cordite. They proved a poor source.

Which nocturnal mammal do British gardeners help by cutting 13 cm 'highway' holes in the base of fences?

Hedgehog highways link gardens so the animals can roam further to find food and nesting sites. By 2025 more than 130,000 volunteers had signed up as Hedgehog Champions.

The Granny Smith apple is named after Maria Ann Smith, who raised it from a chance seedling in which country?

Australia gave the world its famous green apple in 1868, when the seedling sprang up near a creek on her farm at Eastwood, now a suburb of Sydney. Smith had emigrated from Sussex some thirty years earlier.

Which pigment, a poor absorber of green light, captures the energy plants need to make food?

Chlorophyll was isolated and named in 1817 by the French chemists Caventou and Pelletier. Its name joins the Greek words for 'pale green' and 'leaf'.

Which sugary liquid do flowers produce to lure bees, which then carry it home to make honey?

Nectar is made in glands called nectaries purely as a bribe: visitors that come to drink brush against the flower and carry its pollen away. Hummingbirds, moths and even bats are paid the same way.

What do gardeners call a layer of wood chips, straw or leaf mould spread over soil to hold moisture?

Mulch also smothers weed seedlings and evens out soil temperature. Gardeners usually lay it once the ground has warmed up but still holds plenty of moisture.

Which book by biologist Rachel Carson swayed public opinion against DDT and led to a US ban on farm use?

Silent Spring took its title from a Keats poem with the line 'And no birds sing'. Chemical companies fought the 1962 book fiercely, yet it led to the creation of the US Environmental Protection Agency.

Which orange-and-black North American butterfly depends on milkweed as the host plant for its caterpillars?

Monarch caterpillars store the milkweed's heart poisons, which leave the adults toxic and foul-tasting to most birds. Loss of wild milkweed has hit their numbers, so butterfly gardeners plant it.

Which palace beside the Thames has Britain's oldest surviving hedge maze, commissioned by King William III?

Hampton Court had its maze planted in hornbeam around 1690 and later replaced with yew. Reaching the middle takes about 20 minutes, and the puzzle turns up in Jerome K. Jerome's Three Men in a Boat.

Which US president used the gardens of Monticello, his Virginia plantation, to experiment with new plant species?

Thomas Jefferson treated Monticello's beds as a testing ground for new crops, though the long kitchen garden on the slope below Mulberry Row was kept going by enslaved workers.

The Eden Project's giant biome domes were built in a reclaimed china clay pit in which English county?

Cornwall's old pit now holds one of the largest indoor rainforests in the world, under inflated plastic cells on a steel frame. A second biome recreates a Mediterranean climate.

Coir, a springy fibre used in doormats and potting mixes, comes from the outer husk of which fruit?

Coconut husk fibre has been twisted into rope since ancient times, and the word coir comes from Tamil and Malayalam words for cord. Austronesian sailors lashed their plank boats together with it.

Before New Zealand exporters renamed it for the American market, the kiwifruit was sold in English under which name?

Chinese gooseberry was dropped after a US client warned that the name might be causing trouble at quarantine. Jack Turner chose kiwifruit, after the nickname for New Zealanders, to appeal to Americans.

Which term describes trees such as oak and maple that shed all their leaves each autumn?

Deciduous means 'falling off at maturity', and botanists use it for petals and ripe fruit too. In autumn the hormone flow from each leaf fades, and a special layer of cells at its base cuts it loose.

Which stage of a plant's life begins when a dry seed takes in water and its coat splits open?

Germination shows itself when the first root, the radicle, pushes out, with the shoot close behind. Most seeds need enough water to be moistened but not soaked.

Mimosa pudica, nicknamed the sensitive plant, is grown as a curiosity because its leaves do what when touched?

Its leaves fold up and droop at a touch or a shake, then reopen a few minutes later. The trick is costly: each collapse burns energy and interrupts the plant's food-making.

Which New Zealand-born writer set her short story 'The Garden Party' at a wealthy family's lavish lawn gathering?

Katherine Mansfield based the luxurious setting on her childhood home in Wellington. While the Sheridans fuss over the marquee and masses of lilies, word comes that a working-class neighbour has been killed in an accident.

Which naturalist formalised the two-part Latin names, such as Quercus robur for English oak, printed on plant labels?

Carl Linnaeus, a Swedish physician, is known as the father of modern taxonomy. Before he settled on his system, even he described plants with long Latin phrases, as on his expedition to Lapland.

Which English word comes from an old Iranian term for a walled enclosure, later used for Persia's royal gardens?

Paradise began as pairidaeza and reached Greek through Xenophon, who used it for the Persian kings' hunting parks. Bible translators later borrowed the word for the garden of Eden.

The Zen temple Ryōan-ji, famed for a dry garden of rocks set in raked white gravel, is in which Japanese city?

Kyoto's most famous dry garden holds fifteen stones, arranged so that at least one always stays hidden from the viewing veranda. Monks rake the gravel around them every day.

The Boboli Gardens were laid out for the Medici family behind the Pitti Palace in which Italian city?

Florence's grandest garden was made for Eleonora di Toledo, wife of Cosimo I, and it was strictly private: nobody outside the immediate family was allowed in, and no parties are known to have been held there.

Jennie Butchart began the Butchart Gardens on Vancouver Island by planting up what kind of exhausted industrial site?

A limestone quarry had supplied her husband's cement business until it was worked out in 1909. She set about turning the hole into the Sunken Garden, a job that took until 1921.

Nathaniel Bagshaw Ward's sealed glass case, which kept plants alive on long sea journeys, was the forerunner of what?

The terrarium grew from an accident: Ward kept moth cocoons in sealed bottles and found seedlings thriving in a bit of soil inside one. His first cases were tested in 1833 on a voyage lasting months.

Which sunken boundary lets an English landscape garden keep grazing livestock out without blocking the view?

A ha-ha so astonished 18th-century visitors, wrote Horace Walpole, that ordinary people cried 'Ha! Ha!' on meeting the hidden drop. The name first appeared in print in a French gardening book of 1709.

Which head gardener at Chatsworth went on to design the Crystal Palace for the Great Exhibition of 1851?

Joseph Paxton took his cue for the glass palace from the ribbed leaf of a giant water lily he grew at Chatsworth. He also raised the Cavendish banana there, now the most eaten banana in the Western world.

Which crop did plant hunter Robert Fortune take from China to India for the British East India Company?

Tea plants were reportedly forbidden to foreign buyers, so Fortune made some of his journeys disguised as a Chinese merchant. He also brought skilled tea makers to work the company's plantations.

HMS Bounty, seized by Fletcher Christian's mutineers, was carrying which potted plants from Tahiti to the West Indies?

Breadfruit was wanted as cheap food for enslaved plantation workers, so the great cabin became a greenhouse for more than a thousand pots. After the mutiny the crew threw the plants into the sea.

Pteridomania, a Victorian craze named by novelist Charles Kingsley in 1855, was a passion for collecting which plants?

Ferns spread from the garden into pottery, glass and textiles, appearing on everything from christening presents to gravestones. Collectors reached the wetter west and north of Britain on the new railways.

The castor oil plant, widely grown as an ornamental, has mottled bean-like seeds that contain which potent toxin?

Ricin is so potent that four to eight chewed seeds are considered a lethal dose for an adult. Swallowed whole, though, the seeds may pass through the gut without releasing it.

Which vine, shown at the 1876 Centennial Exposition in Philadelphia, was later sold to US farmers to stop soil erosion?

Kudzu was pushed hard in the Dust Bowl years: the Soil Conservation Service grew seventy million seedlings and paid $8 an acre to anyone who would sow it. It now smothers and kills trees by blocking their light.

Which invasive garden plant has led several British lenders to refuse mortgages when it is found on or near a property?

Japanese knotweed has roots that exploit cracks in concrete, asphalt and brick. Researchers call the property damage partly a perceived risk, yet the fear alone has moved house valuations.

What do gardeners call gradually acclimatising seedlings raised under cover to outdoor conditions before planting out?

Hardening off guards against transplant shock, the stress and damage a sheltered plant suffers when it is moved into the open too abruptly.

George Ballas of Houston invented which garden power tool after watching the spinning brushes of an automatic car wash?

String trimmer number one was a tin can laced with fishing line, tried out on an edge trimmer. Ballas called it the Weed Eater because it chewed up the grass and weeds around trees.

Which Roman emperor, wrote Pliny the Elder, was never without cucumbers, which were grown for him in beds on wheels?

Tiberius had the beds rolled out into full sun, and in winter they were drawn back under frames glazed with translucent mirror-stone. The arrangement is counted as an early ancestor of the greenhouse.

Founded in 1545, the world's oldest academic botanical garden still on its original site is in which Italian city?

Padua still grows a dwarf palm planted in 1585, known as Goethe's palm because the poet wrote about it. Pisa's garden was founded a year earlier but has moved twice, so it loses the title.

Which oily compound in poison ivy and poison oak causes an itchy allergic rash in most people who touch it?

Urushiol takes its name from urushi, the Japanese word for the lacquer tree. The same sap that blisters skin hardens into the glossy finish on traditional East Asian lacquerware.

Which composting method ferments food scraps, even cooked leftovers and meat, with inoculated bran in an airtight bin?

Bokashi pickles waste in acid instead of rotting it, much as silage is made, so the closed bin gives off no smell. Once buried, the preserve is eaten by soil life within a few weeks.

What name is given to the partnership in which soil fungi feed minerals to plant roots in exchange for sugars?

Mycorrhiza is the rule rather than the exception: most plant species form one, though the cabbage family cannot. The fungus brings in water, phosphorus and zinc from the surrounding soil.

The lightweight white granules of perlite found in potting mixes are made by heating what until it puffs up?

Volcanic glass with water locked inside is the raw material, usually formed when obsidian hydrates. Strong heat expands it enormously, and the trapped bubbles make the result brilliant white.

Which traditional woodland practice cuts hazel or willow down to a living stump so it regrows as a crop of poles?

Coppicing leaves living stumps called stools, and some are 5.5 metres across, thought to have been cut and recut for centuries. Oak can be worked on a fifty-year cycle for poles or firewood.

The coco de mer palm, which bears the largest seed in the plant kingdom, grows wild only in which island nation?

Seychelles is its only home, on the islands of Praslin and Curieuse. The fruit takes six to seven years to mature and can weigh 45 kg, the heaviest borne by any palm.

Dutch elm disease, a fungus that kills elm trees, is carried from tree to tree mainly by which insects?

Bark beetles spread the spores, and the 'Dutch' honours the scientists, not the source: Christine Buisman and Marie Beatrice Schol-Schwarz identified the disease in the Netherlands from 1921.

Pyrethrum, a natural insecticide long used by gardeners, is made from the dried flower heads of which plant?

Chrysanthemum species from Dalmatia and the Caucasus supply the insect-killing pyrethrins, which is why one is called the Dalmatian chrysanthemum. Some botanists now file both plants under Tanacetum.