WORLD FOOD – Kai pen, An Edible Weed

29 Apr 2002

Laos is not a country in which things tend to happen loudly. It’s a land-locked nation of five million where moments are inhabited and flow, with muted grace, like the Mekong River that forms its eastern border with Thailand. But there are exceptions, and certain foodstuffs are often the ones which endure. What goes on the table comes and goes with the seasons. And one thing people do tend to hoard is kai pen, which grows wild near the old royal capital of Luang Prabang. Nary a Lao will make a trip to the North and not return with several bags of this delicacy.

Kai pen is a weed with a cult following, an artisan transition from raw to edible, and a very short window of appearance – at most several weeks of the year. The uninitiated might not notice, but weather-attuned locals know the season: a transitional wedge, at most two fortnights, somewhere between the cool/dry weather of January and the dead/hot rays of April. Nights are still cool, though the daytime air warns of the coming oppression, and the soil retains just enough vitality to give green life. It is at this time that kai pen sprouts like little tufts of baby hair between heat-exposed rocks on the banks of the Nam Khan and Mekong, the rivers which meet under the steps of Wat Xeng Thong, where Luang Prabang begins .

The upriver villagers who harvest kai pen do so with speed and excitement. So much so that, watch as I may, it is normal to be served kai pen at dinner before realizing it has begun to grow yards away. In its edible form, kai pen is a dark mossy color, wafer thin (and crisp) and lightly fried. It is broken into shards that range in size from playing card to small book. Like all great local foods, kai pen speaks of place and person. Here that means hinting at muggy sweetness, earth and smoke, and a vegetal goodness. The very same reasons that diners will mow through basket upon basket without knowing.

On one side of the kai pen is a sun-dried mosaic of sesame seeds, garlic, and tomatoes. Rather than trumpet their own flavor, these dried components play a supporting role with unconscious elegance. It’s a very Lao way of being. Most commonly kai pen is dipped in a special chili sauce called jaew bong; it is sour-pungent-spicy when made from lime, chilis, garlic, plus the baroque flavoring of dried buffalo skin, a Shan ethnic group specialty (the Shan, a Tai-speaking people, make up the majority of the inhabitants of the area). Though kai pen is often served to ward off hunger while waiting for a main meal, I can’t help but use it in the place of sticky rice to scoop up the warm salads and bitter stews of the Luang Prabang region. Beerlao, light and spritzy, is the normal chaser. When taken with kai pen in alternate mouthfuls, it tends to ward of heat and disappear. Often too quickly.

So how does one make a weed a sought-after taste? On a cool morning this past March I took a long, thin wooden boat up the Mekong to observe for myself. Getting out at Baan Phanom, one of the famed kai pen villages, I saw no weeds sprouting between rocks. As it turns out, the few weeks of wild growth were already over and it had all been gathered. What remained was the process of drying, brushing, seasoning, and preparing. All over the steeply angled banks, near roped-off patches of herbs, army-like rows of woven bamboo mats were covered with sheets of drying kai pen. They stood upon broom-like legs and seemed as if they had walked of the set of Fantasia, dancing in the hot breeze.

Heading up into the village I passed stacks of bamboo mats. I didn’t have to go far – past four playing children, over a few roosters, left of a small temple – to find two young women perched on blue plastic stools hard at work. Surrounding them was a red bowl of fermented water, a basket of the washed and gathered weed – a stunning shade of psychedelic green and sheer as flax – and unused bamboo mats. Paper thin half-moons of tomato, crushed garlic cloves, and white sesame seeds waited in smaller cups as seasoning. Blunt knifes were on hand for reinforcement.

First a bamboo mat would be propped up. A green bunch of kai pen would be turned onto the mat like pastry and, with a wetted brush, patted to sheet-thinness as it morphed from its Technicolor shade to pine to mossy green-black. Once the kai pen was shaped, evenly, into a thin rectangle upon the mat, the moisture would be swatted out with the brush until dripping out the porous bamboo base. After a moment of observation, seasoning would begin. Tomato slices, juicy-sweet, would be thrown on from a foot above. Then garlic scattered like fertilizer. Finally a shower of sesame to fill in the edges. The final product, all abstract shapes and dancing lines, looked uncannily like a Kandinsky composition, when propped up in the sun to dry with dozens of others. For kai pen lovers, though, such work does come fairly cheap, I personally bought two bags to take back down river.

Rob McKeown writes about food, travel, and culture for Food&Wine, Saveur, East, the Boston Globe, Gayot’s/Gault-Millau, and many other publications around the world.

Photo: sunset on the Mekong river (

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