Knotweed Open Season, Week Ending 3/29/2020

You guys! It’s almost knotweed season again! Jump to Recipe

For those of you new to this blog, a brief recap: I have a love-hate relationship with Japanese knotweed (Polygonum cuspidatum, among many other scientific names). This plant is so invasive and so very destructive, it’s classified as a controlled substance in Great Britain. Its roots creep into tiny cracks and crevices in masonry and then expand, slowly destroying… well, anything it reaches.

And on the other hand, Japanese knotweed roots contain so much resveratrol, it is grown as a crop and the extract sold online (you can guess where). And the spring time shoots are ridiculously delicious and abundant. We’re looking at one of the best and worst plants in the world right here!

If you find a patch where you have (or can get) permission to forage, you are doing the local ecosystem a favor by harvesting and eating as much knotweed as you can stand.

A Japanese knotweed shoot - this one is too small to bother eating yet
A Japanese knotweed shoot – this one is too small to bother eating yet

Because winter in the mid-Atlantic failed to make an appearance this year, knotweed growth (like so many signs of spring) is several weeks ahead of where it was last year.

Knotweed has a pronounced sour flavor and works in many recipes that call for rhubarb, and it works well in both savory and sweet dishes. Note for readers who are texture-sensitive: knotweed tends to “melt” as it cooks, and while fans may call it soft, others may consider it mushy.

Harvest stalks that are 12″ or less. If they are taller, but still unbranched, you may still be able to eat them, but the lower parts, near the soil, are more likely to be tough and unpleasant. Store knotweed stalks with the cut ends in water until you are ready to use them.

Store knotweed stalks with their cut ends in water
Store knotweed stalks with their cut ends in water

Remove the leaves and tips; larger stalks may need to be peeled but I usually skip this step. NOTE: Normally I compost every shred of vegetable matter but not knotweed! I have read that even a small piece of knotweed root can regenerate into a whole new plant, so I seal the trimmed bits in a plastic bag and throw them in the garbage. It’s not worth taking any chances!

Remove leaves and tips from knotweed prior to eating
Remove leaves and tips from knotweed prior to eating

Most vegetables fare well with a simple treatment of roasting and Parmesan cheese, and knotweed is no exception. Unfortunately once cooked, knotweed loses most of its photogenic color and texture, so you’ll have to trust me on how amazing this side dish tastes!

Parmesan Roasted Knotweed
Parmesan Roasted Knotweed



  • 1/2 lb trimmed Japanese knotweed stalks
  • 1/4 cup melted butter
  • 1/4 cup shredded parmigiano reggiano
  • salt and fresh cracked pepper to taste


Preheat oven to 400 degrees F.

Cut larger knotweed stalks in half lengthwise; thinner stalks can be left whole. Place knotweed in a oven-safe pan with 1/2 cup of water. Cover and simmer on low for 4 – 5 minutes until knotweed is soft. Drain excess water.

Season knotweed with salt and pepper and drizzle with melted butter. Roast the vegetables for 10 minutes, then sprinkle evenly with parmesan cheese. Return the pan to the oven for another 5 minutes, or until the cheese is melted and lightly browned. (You could also use the broiler on high for a few minutes if preferred.)

 I will try not to inundate you with knotweed recipes, but no promises! I do believe “biological control” – aka foraging – is one of the best weapons we have against the spread of this species!

NOTE: While Japanese knotweed is generally considered safe, always, always, always sample a small bit to make sure you have no bad reactions. But even more of a concern is that Japanese knotweed infestations are usually treated with glyphosate-based herbicides (though often with limited success), and those chemicals could linger in the area. If you have any doubts at all, about herbicide use, consider finding a different patch to enjoy!

What’s your favorite way to enjoy knotweed? What other spring edibles are making an appearance your world right now?

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