I'd spent hours and hours combing the WWOOF Handbook trying to work out which was the best place to Wwoof, so to speak. In the end I chose the entry that sounded the most interesting. As I sat waiting to be picked up I was beginning to feel that maybe I should have plumped for "relaxing" rather than "interesting"; maybe I should have picked the "Tree planting English teachers" or the "Banana Plantation" rather than the "Zen Buddhist woodcarvers".

I relaxed a little when a battered burgundy van pulled up and a tall thin German with thick greying tied-back hair jumped out. Shaking my hand, he introduced himself as Armin. By the time we had arrived at "The Flying Cow" (a spectacularly elegant spacious house) and I had met the small smiling Asuka, I knew I'd made the right decision. As it turned out, and I suspect this is a common phenomenon, the interpretation of Wwoofing was a liberal one. They do have an organic mandarin orchard, but a lack of orders meant no picking was required. And so I was directed towards the garden. My traditional image of gardens owned by Zen Buddhists are the ones with a bunch of boulders, a load of gravel raked into swirling patterns and maybe the odd dollop of moss here and there. The most that would be required was a few deft swishes of a rake. I couldn't have been more wrong. Armin and Asuka's house sits atop the crest of a small valley. Behind, paths weave down through a green and gold garden to the bubbling river below. The valley climbs again on the opposite bank, now covered in lush forest that extends as far as the eye can see.

A garden this size needs a lot of tending - and this was to be my task. The soil quality alternates between a mixture of rubble and baked clay, and damp sand, which means everything needs a helping hand if it is going to grow at all. Armin explained this as he, slightly sheepishly, handed me a bag of pellets of concentrated fertiliser. So much for the Wwoofing; I was becoming a Willing Worker On a Somewhat Inorganic Garden. Some of the garden gave up the unequal struggle in this environment but other parts seemed to relish it and ran decidedly rampant. I spent a great deal of time hacking away at a "ground cover" plant that had somehow misinterpreted its mission brief and decided that this meant covering the ground and everything attached to it, including its fellow garden residents.

As I sliced away at the thick matted network of branches and roots, hidden plants burst forth, stretched in the sunlight and issued an almost audible sigh of relief. Unfortunately, during my surgery I repeatedly exposed shoals of sandflies that had been quietly snoozing in the damp warmth of the vegetation. Sandflies are one of New Zealand's less marketable indigenous wildlife icons - larger than a gnat and smaller than a mosquito, they have the same prodigious lust for blood but without the social decency to administer an anaesthetic first. As a consequence you can very clearly feel exactly when they are puncturing your skin. By the end of the day my arms were a mosaic of red blotches. The next day I drenched myself in noxious insect repellent.

Asuka and Armin make no money from their garden and only a small amount from their mandarin orchard. Their main source of income is woodcarving from a particular wood - Kauri. This tree, native to New Zealand, is now protected by law and no-one is allowed to cut one down. We visited one of the few remaining Kauri forests nearby and I could see why. Kauri are tall and fat, and they can live for well over 2,000 years (the record is around 4,000). This is because the wood is exceptionally strong and the trees are nearly perfectly straight. They stand, like stone columns, rising from the forest floor, branchless until the sudden broad canopy 30 metres overhead.

Unfortunately for the Kauri, because it is so strong and straight it is also rather useful. This has been, literally, its downfall. There is so little left that it is protected. Armin hasn't taken to sneaking into the woods at night with a chainsaw to obtain his materials - there is another source of Kauri. Over the millennia, Kauri have died and toppled to the forest floor, sinking slowly into the soggy still soil. Generations passed and Kauri piled onto Kauri. The result is that swamps and forests today sit upon huge stacks of Kauri wood embedded deep under the soil. It's still OK to mine this Kauri and this is where Armin gets his wood. It's old too and still recognisable as wood, having been perfectly preserved in a damp oxygen-free environment. Some of it is over 50,000 years old - making it probably the world's oldest wood.

This is the main reason, Armin says, why it sells. Exactly the same thing - equally as beautiful - but made out of pine, just does not sell. People want Kauri, and are prepared to pay through the nose for it - all the better for Armin and Asuka. As he stoked the house fire and threw another handful of unusable Kauri offcuts into the flames I couldn't help thinking it was a rather ignominious end to a 50,000 year journey.

Being Zen Buddhists, Armin and Asuka meditate every evening and they ask all their visitors to join them. Apparently this has frightened off people in the past, but since all that is required is to sit still for half an hour I didn't find it too difficult, being a rather sedentary creature by nature. I have to admit that I spent rather a lot of the time contemplating the forthcoming dinner, rather that say, the ineffable infinite. The Flying Cow was the only entry in the WWOOF handbook that explicitly said "vegans welcome" (one actually said "NO vegans"!) and the food that Asuka and Armin cooked was superbly delicious - Armin's salads were consistently perfect and Asuka's miso soup the best I've ever tasted. We even had Umeboshi - the spiced salty Japanese plums that I'd last had in Thailand - utterly delicious!

I left this morning - getting a lift back into Kerikeri with Armin. I'm going to miss eating the food, listening to Kiwi calls through the night and waking up to the forest panorama. But what I'll miss most of all will be the tall greying German and the short smiling Japanese woman: Armin and Asuka.