Landscaping: World's weirdest plantings

The Alnwick Poison Gardens in England.

Ever since I wrote about British gardener Stuart Grindle's lawn obsession a few weeks ago, I've had to stop myself mowing ours more frequently than once a week. Grindle, who's 70, mows twice a day, three times a week, to keep each blade a uniform 5mm long.

At the other end of the scale, I discovered an 80-year-old man who planted a garden in 1960 and last watered it in 1972. And yes, it's still thriving. David Latimer planted his garden in a bottle and sealed it shut 40-odd years ago as an experiment to see if it would survive.

The hardy spiderwort plant inside has grown to fill the 38-litre container by surviving entirely on recycled air, nutrients and water. The water in the bottle gets taken up by the roots, is released into the air during transpiration, condenses down into the potting mixture, where the cycle begins again. Clever.

Almost as clever is a garden so poisonous you can enter it only with a fully qualified guide. The creation of Alnwick Poison Gardens in Northumberland, England, was inspired by the legendary botanical gardens in Padua, where the Medicis plotted to bring their enemies to a mouth-frothing end.

An English duchess created this garden, dedicating it entirely to flora that is deadly and/or narcotic. The tall, black gates imprison about 100 killers including belladonna and hemlock. Wanting in part to hark back to old apothecary gardens, she shied away from healing medicinals and sought out deadly poisons.

She has also cultivated narcotic plants such as opium poppies, cannabis and tobacco, many of which can be grown only with special government permission. Some plants are so deadly they are caged, and the garden is under a 24-hour security watch. Makes my oleander and datura look like pussycats by comparison.

And scarily, Alnwick is not the only garden in the world dedicated to murderous plants. Amy Stewart, author of the book Wicked Plants: The Weed That Killed Lincoln's Mother and Other Botanical Atrocities, has a small poison garden at her home in California. Stewart's garden has more than 35 species that can wreak havoc on humankind if mishandled.

The roof garden on the Museum of Modern Art in New York (left) is designed for a birds-eye view.

Happily, not all the weird gardens of the world are poisonous. Sydney has the world's tallest vertical garden, with greenery climbing more than 160m and 15 storeys high up the One Central Park building. It may soon be overtaken by vertical gardens on the 46-floor apartment building under construction in Sri Lanka.

There's no opportunity to admire at close range the features of the new roof garden at the Museum of Modern Art in New York. Created solely as art for working Manhattanites to look down on from above, the garden isn't even accessible. And probably just as well - it's made of crushed stone, recycled glass, recycled rubber mulch, fibreglass gratings, PVC fittings and artificial plants. Not the sort of place you'd want to eat your packed lunch, anyway.

Ben Hoyle's display at the Ellerslie Flower Show.

Top 10 gardens A Google search for "the world's 10 best gardens" brings up hundreds of contenders. On one top 10 list I was delighted to find a display garden from last year's Ellerslie Flower Show. Named "A French Kiss in Akaroa", the garden by designer Ben Hoyle included a huge floating vine parterre over black water canvas. Islands of perennials were captured within the vine, and it included a pit filled with cushions where visitors could take in a perspective from below the waterline.

And if you thought it was hard to grow beautiful gardens in Invercargill, Stewart Island or the Chathams, take heart from the Arctic-Alpine Botanic Garden in Troms, Norway. It's the most northern botanical garden in the world and home to an impressive display of plants from all over the world.