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 garden pea germinates, flowers, sets seed and dies within one growing season, so it must be sown afresh each year.

Parsley and Canterbury bells take how long to complete their life cycle?

Two years: parsley and Canterbury bells are biennials, spending their first year growing leaves and roots, then flowering, setting seed and dying in the second.

Grass clippings and food scraps, the 'greens' of a compost heap, are rich in what?

Green waste such as grass clippings is rich in nitrogen; 'browns' like paper and wood chips supply carbon, and a ratio of about 30:1 carbon to nitrogen composts best.

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

K stands for potassium, from its Latin name kalium; with N for nitrogen and P for phosphorus it makes up the three macronutrients printed on every fertiliser bag.

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

A pH below 7 is acidic; blueberries and rhododendrons thrive in acidic soil around pH 4.5 to 5.5, while most vegetables prefer a near-neutral 6 to 7.

In acidic, low-pH 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's 1881 book The Formation of Vegetable Mould through the Action of Worms estimated that an acre of arable land could hold about 53,000 of them.

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 trains a fruit tree flat against a wall or wires in horizontal tiers; a single-tier, free-standing version is called a step-over.

The Chinese art that parallels Japanese bonsai is called what?

Penjing, the Chinese art of miniature trees and landscapes in trays, predates and inspired Japanese bonsai; Korea's equivalent is bunjae and Vietnam's is hòn non bộ.

Which of these shrubs is a classic choice for topiary?

Box (Buxus) is the classic topiary shrub, dense and tolerant of hard clipping; yew, bay, holly and privet are the other regulars.

Kew Gardens in London, a World Heritage Site, was founded in which year?

Kew was founded in 1759, when Princess Augusta, mother of George III, began a nine-acre botanic garden on the estate; it became a World Heritage Site in 2003.

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

André Le Nôtre laid out the gardens of Versailles for Louis XIV from 1661, with the Grand Canal, parterres and fountains that define the French formal style.

About how many flower bulbs are planted each year at Keukenhof in the Netherlands?

About 7 million bulbs are hand-planted each autumn in the 32-hectare park at Lisse, which opens for roughly eight weeks each spring and is best known for its tulips.

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.

The Hanging Gardens of Babylon are unique among the Seven Wonders of the Ancient World for what reason?

Legend says Nebuchadnezzar II built them for his wife Amytis, who missed the green hills of her homeland; some scholars now place them at Nineveh.

How did the 18th-century landscape gardener Lancelot Brown earn his famous nickname?

He designed more than 170 parks, including Blenheim, and many survive today.

Gertrude Jekyll is best remembered for her garden partnership with which architect?

Edwin Lutyens designed the houses and Gertrude Jekyll the planting on some 100 projects, beginning with her own home, Munstead Wood in Surrey, which he built in 1896.

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

Burbank introduced the Shasta daisy in 1901 after years of crossing daisy species; his other successes include the Santa Rosa plum, the plumcot and a spineless cactus.

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

Alan Titchmarsh left Gardeners' World in 2002 after six years as lead presenter; Monty Don took over in 2003 and later fronted the show from his own garden, Longmeadow.

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?

The corn supports the beans, the beans fix nitrogen and the squash leaves shade out weeds and hold moisture.

Tulip mania, the famous speculative bubble, collapsed in which year?

Prices collapsed in February 1637; at the peak a single Viceroy bulb was offered for 3,000 to 4,200 guilders, when a skilled craftsman earned about 300 guilders a year.

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

All are members of the rose family, Rosaceae, which also gives us plums, peaches, raspberries, quinces and hawthorn.

The dahlia is the national flower of which country?

Mexico declared the dahlia its national flower in 1963; the Aztecs grew it 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?

Ladybirds and their larvae eat aphids, an adult taking up to 50 a day, which is why gardeners welcome them on roses and broad beans.

The 'lady' in ladybird refers to whom?

The name comes from 'Our Lady's bird', a medieval dedication to the Virgin Mary; the seven-spot's red wings were likened to her cloak and its spots to her seven joys and sorrows.

Which First Lady planted a victory garden on the White House lawn in 1943?

Eleanor Roosevelt planted a victory garden on the White House lawn in 1943 over the objections of the Department of Agriculture; Americans tended some 20 million victory gardens that year.

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

The Chelsea Flower Show has been held in the grounds of the Royal Hospital Chelsea since 1913; the RHS's Great Spring Show began at its Kensington garden in 1862.

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

The society was suggested in 1800 by John Wedgwood, son of the potter Josiah, and now runs five gardens.

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

It opened in February 2008 and passed a million samples in 2018; the Norwegian government paid the whole construction cost.

The USDA plant hardiness zones are based on what measurement?

Each zone spans 10 degrees Fahrenheit of average annual extreme minimum temperature; there are 13 zones, so a plant hardy to zone 10 can take a winter low of 30 to 40°F.

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?

Rhubarb leaves contain about 0.5 per cent oxalic acid by weight, plus anthraquinone glycosides, enough to cause kidney damage if eaten in quantity; the stalks hold far less.

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.

The world's largest wisteria, covering over an acre and weighing about 250 tons, is in which state?

The Sierra Madre Wistaria in California, planted in 1894 from a single vine, sprawls across two private gardens and was listed by Guinness as the world's largest blossoming plant.

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

Its jaws snap when tiny trigger hairs are touched, sometimes within a tenth of a second.

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?

Rhizobium bacteria in the nodules fix nitrogen from the air into a form the plant can use; digging a legume crop in can add 40 to 200 pounds of nitrogen per acre.

New York's Central Park was designed in 1858 by Calvert Vaux and which landscape architect?

Frederick Law Olmsted and Calvert Vaux won the 1858 design competition with their Greensward Plan; the park they laid out covers 843 acres of Manhattan.

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

Frances Hodgson Burnett, also the author of Little Lord Fauntleroy, wrote The Secret Garden; it was serialised in The American Magazine from 1910 before appearing as a book in 1911.

Vita Sackville-West created the garden at Sissinghurst in Kent with her husband, who was?

Harold Nicolson, diplomat and diarist, laid out Sissinghurst's formal structure from 1930 while Vita Sackville-West did the planting; she also wrote The Observer's gardening column from 1946 to 1961.

The Flower Dome at Singapore's Gardens by the Bay holds what record?

The Flower Dome, with 1.2 hectares under glass, was recognised by Guinness World Records in 2015 as the world's largest glass greenhouse; the park beside Marina Reservoir also holds the Supertree Grove.

Many gardeners say a variety must date from before which year to count as an heirloom?

1951 is the cut-off many use because widely sold hybrid seed arrived around then; other definitions simply require a variety to be 50 or 100 years old.

'Guerrilla gardening' was first used in 1973 by Liz Christy and her Green Guerrilla group in which city?

Liz Christy's Green Guerrillas began in 1973 on the Lower East Side of New York, turning a vacant lot at Bowery and Houston into 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.

The Chelsea Physic Garden was founded in London in 1673 by which group to grow medicinal plants?

The Worshipful Society of Apothecaries founded the garden in 1673 to train apprentices in identifying medicinal plants; it is England's second-oldest botanic garden, after Oxford's of 1621.

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

Mendel bred garden peas (Pisum sativum) at the Brno monastery between 1856 and 1863, tracking seven traits including plant height, pod shape and flower colour.

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

Digoxin is extracted from the foxglove, chiefly the woolly foxglove Digitalis lanata; the plant is a biennial that sends up its tall spike in its second year, and every part is toxic.

The sweet pea, prized for its scent, is native to which Mediterranean island?

Sicily: the Franciscan monk Francesco Cupani described the sweet pea there in 1696 and sent seed to England in 1699; unlike the garden pea, its seeds are mildly toxic.

The lawn mower was invented in 1830 by Edwin Budding in which English county?

Edwin Budding patented his 19-inch cylinder mower in 1830 at Thrupp, near Stroud in Gloucestershire, as an alternative to the scythe for sports grounds and large gardens.

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 rhododendron, lali gurans (Rhododendron arboreum), which colours its hills red each spring; it is also the state flower of Washington and West Virginia.

A cold frame protects young plants with what kind of roof?

It lets sunlight in by day and traps heat at night, and is used to harden off seedlings before planting out.

In horticulture, what does the branch called pomology study?

Pomology is the study of fruit, from the Latin pomum, 'fruit'; vegetable growing is olericulture and flower growing is floriculture.

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

Vernalization is exposure to prolonged cold, typically weeks at 0 to 10°C; without a winter, or a spell in the fridge, winter wheat and many biennials will not flower.

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

Trofim Lysenko coined 'yarovizatsiya' in 1928 for his cold treatment of winter wheat; the science had been laid out in 1918 by the German physiologist Gustav Gassner.

Whose 1627 book Sylva Sylvarum contains the earliest published work on growing land plants without soil?

Francis Bacon's Sylva Sylvarum appeared in 1627, a year after his death; John Woodward followed in 1699 with water-culture experiments on spearmint.

In hydroponics, what does the abbreviation NFT stand for?

Nutrient film technique: a shallow film of nutrient solution is recirculated past bare roots in a sloping channel, so the roots get water and air at once; Allen Cooper developed it in England in the 1960s.

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

Etiolation: the stems stretch toward any light and stay pale because no chlorophyll is made, which is exactly how forced rhubarb and white asparagus are produced.

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; basil, beetroot, brassicas, onions and leeks are prone to bolting too.

Which Cornell botanist pioneered micropropagation and tissue culture in the late 1950s?

Frederick Campion Steward's 1958 carrot-cell experiments at Cornell showed a single cell could regrow a whole plant, the basis of mass-produced orchids and disease-free seed potatoes.

Which propagation technique, also called marcotting, roots a branch while still attached to the parent plant?

Air layering: the stem is girdled, wrapped in damp moss and plastic, and cut free once roots form; it is widely used on figs, magnolias, citrus and rubber plants that root poorly 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?

Auxins: the usual active ingredient is indole-3-butyric acid (IBA), a close relative of the plant's own auxin indole-3-acetic acid, and it triggers root formation at the cut.

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

Chlorosis is yellowing from too little chlorophyll; on limy soils iron is locked up, and French vine growers call that version chlorose calcaire. Magnesium and zinc shortages cause it too.

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 day and night length, documented in 1920, called?

Photoperiodism, described by Garner and Allard in 1920, is why poinsettias and chrysanthemums are given long nights under blackout cloth to flower for the holidays.

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.