YOU may be opening your front door to mischievous trick or treaters in ghoulish guises this Hallowe’en, but peep into your back garden and you could also spot some stinking, spiky and poisonous subjects.

While would-be wizards and witches may be taunting you on your doorstep, in your garden you may experience something equally sinister. Some plants can sting, burn, cut you or emit an acrid, foul-smelling odour.

Among the most prickly of plants is the hawthorn. As a thorny hedge, it will deter even the most persistent burglar. The thorns of mature plants can pierce the toughest glove and I’ve often had to pick them out of my thick gardening clogs to stop them from pricking my toes.

It features among the Metropolitan Police list of top shrubs for deterring thieves. Other prickly candidates include creeping juniper, common holly, firethorn (pyracantha), juniper and purple berberis.The Met advises people to plant hedges of such unfriendly shrubs to use nature’s own defence mechanisms and keep out burglars.

Then there are the plants which don’t smell quite as sweet as you’d like. In fact they stink. Take the titan arum (Amorphophallus titanum) and the dragon arum (Dracunculus vulgaris). Both smell like rotting corpses when in flower, to attract pollinating flies.

The titan arum, also known as the ‘corpse flower’ for obvious reasons, is nevertheless beautiful, growing to 3m tall, its gigantic crimson flower spanning 3m and is a great magnet for pollinating insects. You won’t find it in the average British garden, though, as it prefers the rainforests of Sumatra as its natural habitat, although you can admire it in the exotic sections of botanical gardens such as the Eden Project in Cornwall and at Kew.

Then there’s stinking iris, Iris foetidissima, whose leaves have a pungent scent but which comes into its own visually in autumn and winter, putting on a spectacular display when its huge seed pods burst open to reveal brilliant orange, sometimes red, seeds. They cling to the pods throughout the winter until the spring, and are ignored by birds.

Others in the bad smells league include Eucomis bicolor, the pineapple lily, and the dead horse arum (Helicodiceros muscivorus), named for obvious reasons.

While many bulbs bring heady fragrance to spring, including the sweetly scented hyacinth, others have pretty horrible odours including the imposing crown imperial (Fritillaria imperialis).No Hallowe’en would be complete without its share of witches, whose potions have been linked with some of our most common plants.

Hemlock, for instance, is highly poisonous and closely linked with witchcraft. It doesn’t look significantly different from the hedge parsley or cow parsley which grows along roads, ditches, trails, or the edges of fields.

There is beauty in all, even the most sinister of subjects. So enjoy Hallowe’en, but just remember the plants with slightly darker properties, hidden in the nooks and crannies of your garden.