Rachel Lambert: forager, author, guide

Japanese knotweed jam recipe

Luscious spoonful of foraged Japanese knotweed

A delectably thick, fruity-flavoured jam which is gorgeous as a layer in Japanese knotweed frangipane or lathered onto toast.

If your not familiar with this as an edible wild food, I highly recommend it for flavour, health benefits and as a way to manage the spread of this invasive plant. Find out more about Japanese knotweed on these blogs; Eating Japanese knotweed and Tricks for making Japanese knotweed edible. Meanwhile, here's the recipe....

Spoonful of foraged Japanese knotweed jam

Japanese Knotweed Jam recipe

To make this recipe you'll first need to make a puree from the knotweed. This is an unembellished, unsweetened ingredient for cake, jam or savoury recipes. The leftover liquid is also perfect for making Japanese knotweed syrup.

Makes 500 g (2 ½ cups)


  • 1 kg (2 lb/10 cups) peeled knotweed, leaves, tops and papery notches removed*, 1-2 cm slices
  • 375 ml (1 ½ cups) water**

Chop the knotweed into 1-2 cm pieces and place with the water in a medium to large saucepan on a medium heat. Bring to the boil then simmer for 15 minutes or until soft and mushy. Mash the pulp a little and if you’re confident it doesn’t contain hard, fibrous parts you can use the puree as it is. If not, press through a colander or large-holed sieve into a large bowl and discard the fibrous pulp left in the colander. Place the smooth pulp in a jelly bag over a bowl and allow the liquid to drip through for an hour. Put the liquid aside for making syrup (see below) and the puree is ready to use or can be frozen until needed.

*The base of Japanese knotweed and outer layer of older stems can be quite fibrous and are best discarded. On younger stems, peel where needed, but most of the outer parts will soften well with cooking and don’t need to be removed.

**If using rhubarb, only add 125 ml (½ cup) of water. The rhubarb shouldn’t need peeling or sieving, though I find it makes 50-100 g less puree.

Luscious spoonful of foraged Japanese knotweed

Japanese knotweed jam

Now you have the puree you can make the jam - it is delectably thick, with a surprisingly fruity-flavoured which is gorgeous as a layer in Japanese knotweed frangipane or lathered onto toast.

Makes 400 g


  • 300 g (1 ½ cups) Japanese knotweed puree
  • 300 g (1 ½ cups) soft brown sugar
Making jam from Japanese knotweed - picked on a wild food course

Place both the puree and sugar in a small pan over a medium heat and bring to the boil while stirring. Allow to bubble for 15 minutes or until it reaches 95°C/200°F, checking that it doesn’t burn. I find the mixture spits a lot, so use a splatter guard or cover with a tipped lid to stop it getting everywhere. It’s ready when dark, thick and drops heavily off the spoon. Store in a sterilised jar or use for Japanese knotweed frangipane.

Luscious spoonful of foraged Japanese knotweed

2 comments on “Japanese knotweed jam recipe”

  1. I enjoy reading, imagining and looking at photos.... still not making the time to make the jams . Look so yummy

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