Way of the triffids: The arisaema may look sinister, but it has benign intentions

Anna Pavord explores a Nepalese-style garden

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The Independent Online

I rather like plants that look as though they might snatch you from your bed and eat you up. Which is why it was impossible to leave Craigieburn, near Moffat in the Borders, without one of Dawa Sherpa's special arisaemas. How he manages to keep this animal in a pot, I can't imagine. Its vast blackish leaves loom, tripartite, over fat, even blacker stems at least a metre tall. Close to the ground crouches a terrifying black pouch-like spathe, protecting the spadix almost hidden inside. If you put a finger inside this spathe, you'd come away without it. Well, that's how it seemed to me anyway.

How did this fantastic creature ever arrive in the well-mannered Borders? Craigieburn's owner, Janet Wheatcroft, told me the story. She was in Nepal, looking at meconopsis with a guide – Dawa Sherpa. The fast-flowing river beside which they were camping rose after a storm, and in trying to cross it, she got into difficulties. She would certainly have drowned, she says, if Dawa Sherpa had not put his own life at risk by rescuing her.

Later, she invited him and his family to Craigieburn. And they stayed. Which is why the garden now gives you as close a representation of the Himalayan foothills as you'll find away from the real thing. Prayer flags flutter from small hillocks. There's a fine stupa, and down to the right-hand side of the Wheatcrofts' handsome house, built close to the noisy, energetic waters of the burn, there's a rocky Sherpa garden, planted with all the things that grow around Dawa Sherpa's own village in Nepal. Including the massive arisaemas.

In this country, they are sometimes known as cobra lilies, though there is absolutely nothing lily-ish about them. They do dangerous, not pretty. I started growing them about eight years ago, tentatively at first, as I was not sure I could make them happy. They want moist, but well-drained soil, rich in humus, somewhere coolish and partly shaded. In the wild, they come from Bhutan, Nepal, Sikkim, the eastern Himalayas and western China. We've seen them sometimes when moving through Sikkim, but we're generally there in November, by which time the leaves and spadix of the arisaemas have withered away and only the bright fruit are left.

The first one I planted, Arisaema consanguineum, is now well established, more than a metre tall, with a few little babies round its feet. The solitary leaf rises on a tall, palely mottled stem and spins out in a Catherine wheel of leaflets, sometimes as many as 20. The leaflets are drawn out into long spidery tips which spill water away from the centre of the plant. The spathe, which grows out halfway up the stem, is palely striped in greenish-white and like the leaflets, ends in a long, thin tail. This species will tolerate some sun and in terms of form, is one of the most splendid of all the tribe.

Since that first arisaema, I've introduced six more, a new one each year. The tubers are quite pricey (I paid £8.50 for my first) but once you've started to understand what they want, the chances of losing them are slight. So far, the badgers, which dig down and eat all our special arums, leave the arisaemas alone. Dawa Sherpa says that the cattle in his village never touched them either.

So, the good news is that arisaemas are not as tender as their tropical looks might suggest. And though weird and witchy, they make splendid garden plants. The foliage is spectacular, standing in splendid fettle long after the strange cobra-headed inflorescences have melted away. The first mottled snouts of the plants push through the ground in late May and the last kinds stand well into July. They are sinister and fabulously seductive.

More than 80 different kinds are listed in The Plant Finder, nearly all of them species. The taller kinds look good among equally imposing ferns, such as Osmunda regalis, or Hosta 'Krossa Regal' or Thalictrum chelidonii. The smaller ones can erupt by mounds of Adiantum pedatum and the Himalayan maidenhair fern, Adiantum venustum. At the moment, I'm transfixed by this year's new arrival, Arisaema costatum, which has leaves arranged like the ace of clubs. In itself, this isn't an unusual form among arisaemas, but in this species, the colour – a brilliant emerald green – is as mesmerising as the texture of the foliage, each leaflet delicately ribbed like slubbed silk. The spathe is striped in white and brown, again, not an unusual arrangement. But from the inside, the white glows brilliantly, as if it's lit up – like a stained-glass window with the sun behind it. It is an extraordinary trick and I know of no other plant that can produce the same effect.

I get hold of tubers in spring and plant them up individually in deep pots. When the snout emerges, I plant them out. This way, I remember where they are. Set the tubers about 25cm deep in somewhere moist, rich and shady. They need to be deep because roots come from the top of the tuber, not the bottom. If it is not clear to you which is which, plant the tuber on its side. Many are happiest in soils that are the acid side of neutral. Mulch with compost or leaf mould in autumn or winter. If shade is hard to provide in your particular patch, stick to A. candidissimum, A. consanguineum and A. jacquemontii which can take more sun than the other kinds.

Arisaemas grow well in pots, provided they are big and deep enough. Species with potentially large tubers, such as A. griffithii, A speciosum, and A. tortuosum should be in pots at least 25cm across. Use a loam-based compost mixed with grit (two parts compost to one part grit) adding some well-rotted leaf mould if you have it. Water freely once the leaves start to unfold, and feed with a liquid fertiliser once a month. A dressing of crushed bark on top of the compost helps to retain moisture. Some arisaemas are frost hardy rather than fully hardy, so in really cold winters, pots will need protection.

Though deer, badgers, rabbits and mice leave arisaemas alone, slugs and snails don't. They love the juicy spears as they come through the ground in early summer. Sadly, a spathe loses its allure once it has been done over by molluscs. Be prepared.

Craigieburn, by Moffat, Dumfriesshire DG10 9LF, 01683 221250, craigieburngarden.com. Arisaemas are available from Rare Plants, PO Box 468, Wrexham LL13 9XR (rareplants.co.uk), Cotswold Garden Flowers, Sands Lane, Badsey, Evesham, Worcs WR11 7EZ (cgf.net), Hardy Exotics, Gilly Lane, Whitecross, Penzance, Cornwall TR20 8BZ (hardyexotics.co.uk), Westonbirt Plants, 17 Stanley Rd, Carshalton, Surrey SM5 4LE (westonbirtplants.co.uk), Pan-Global Plants, The Walled Garden, Frampton Ct, Frampton-on-Severn, Glos GL2 7EX (panglobalplants.com)