Hermitcraft: Knotweed Shoots

Japanese knotweed (Polygonum cuspidatum syn. Fallopia japonica) and giant knotweed (P. sachalinense syn. F. sachalinensis) are sending up their fat shoots now in the Northern Hemisphere, and thanks to their ubiquity, promiscuity, and flavour, they're well worth knowing about. The sprouts resemble fat asparagus, but have a tangy, earthy, rhubarb-like quality that's equally at home in sweet or savoury dishes.

Japanese knotweed reaches about six feet, with six- to eight-inch leaves; giant knotweed is noticeably bigger. They prefer moist, rich soil, where they form a dense monoculture; the bamboo-like dead canes persist through winter, making patches easy to locate and identify. Widely introduced outside their native Asia, both species are fiercely invasive and have become pests throughout the temperate world, prompting eradication campaigns.

In spring, brick red, fingertip-sized nubs appear at the base of the dead canes; they soon grow an inch or two and turn white, at which point they are mildly toxic. A day or two later they will spurt up to their six-inch asparagus-looking stage, doubling in diameter and turning green with red highlights, with sticky, papery collars at the joints. Then they can be simmered in water, stock, or wine with garlic and onion and run through a blender to make an outstanding vélouté (creamy soup).

When those left behind reach one to two feet, with a few small leaves, well-developed joints, and a stringy, fibrous sheath, they become too tough to be cooked as a vegetable. On the other hand they gain a lot of tartness, so the tough skin can be peeled away and the stem sliced into translucent bright green rings for use in rhubarb-like sauces, jams, and pies. Finally, when the remaining shoots turn bitter, generally at about two feet, they're toxic again; the season is closed for another year.

Knotweed is high in vitamin C and other nutrients that creatures coming out of hibernation crave. Given that its flavour is pleasantly intriguing, it would seem the only thing standing between knotweed and the mainstream is the name. I just tell fussy guests it’s “Japanese asparagus” ("Japanese rhubarb" in the case of pie or jam) and everyone’s happy.

Including the local ecosystem.

(Adapted from my book The Neighborhood Forager, Copyright 1999 Chelsea Green Publishers, White River VT.)