composting perennial weeds

Disposing of perennial weeds presents a problem for the gardener. Nettles, couch grass and bindweed all have apparently indestructible roots that will re-infest the ground if allowed back into the soil.

Put them into the compost bins and they will flourish and not die. Instead of the crumbly soil pick-me-up that finished compost should be, composted perennial weeds will gain vigour and go back into the soil energised and insurgent.

Lawrence Hills suggested leaving perennials to completely dry out on mesh before their dessicated 'pirates hoard of robbed nutrients' could be added to the compost. I have found this method is only practicable if the volume of perennial weeds is small and the summer hot and dry. In the winter, perennial roots would not be killed using this system.

Bob Flowerdew's preferred method is to drown perennial weeds. Place perennial weeds into a bucket, fill with water and place lid on tightly. Roots and seeds will be killed by a long submersion in the dark. They may then be added to the compost. The liquid 'leachate' can be drained and stored to be used in a highly dilute form as a nitrogenous plant feed. 'Leachate' is any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed. Pictured is the unsavoury contents of a bucket of drowned weeds with the fruits of happy fungi just showing on the surface.


Garden Organic recommends bagging perennial weeds to kill them. Without light they will die and the contents of the bag can then be added to the compost. The process of decomposition can be speeded inside the individual bags if grass cuttings are added. Although requiring storage space, this method does allow the gardener blessed with lots of perennial weeds to process them fairly easily. I keep mine in an old builders' bag for ease of storage.

Instead of the acrid smell that comes from anti-social, slow smoking bonfires heaped with soggy weeds, you will now have barrows full of the best organic soil conditioner a gardener could ever want.