How to: dispose of weeds thoughtfully

An important part of supporting local biodiversity is tackling introduced and invasive plant species. Whether it's being part of a bushcare or Landcare group in a natural area or caring for privately owned land, the struggle to keep on top of weeds is seemingly endless. I often get questions about what to do with the organic matter accumulated through weeding, and there's a lot of uncertainty about what is safe and what is feasible.

Unfortunately, there are many different factors to take into account when managing weeds. These include the characteristics of the species you're tackling, and the volume of material you will be producing. Principles include disturbing the soil as little as possible, leaving as much organic matter on site as possible, and minimising the amount of follow-up work required.  

My main purpose with this post is to make it clear that, across the Kiama, Shellharbour and Wollongong LGAs, green waste bins are suitable for composting weeds, including weed seeds of all kinds, and 'problem weeds' such as Trad (Tradescantia fluminensis) or Cape Ivy (Delairea odorata) that can regrow from a small piece of stem or leaf. Seeds and 'problem weeds' are a particular challenge: they can't just be left on the ground, as they'll only produce more weeds!

This green bin contains a few weeds that will regrow if not carefully managed, including Kikuyu (Cenchrus clandestina), Buffalo Grass (Bouteloua dactyloides) and Trad (Tradescantia fluminensis). 

I checked in with local councils and with the teams managing green waste across the three LGAs, as well as reviewing relevant webpages. And I can confirm that green waste in all three LGAs is treated via hot composting in tunnel systems for between 14 and 21 days. This is sufficient to kill all weeds as well as other nasties such as E. coli. You can read more about it online, for example 

If you do have green waste that can't go in your green bin for whatever reason, and more generally to reduce the amount of organic matter taken off-site, weed management techniques from bush regeneration may come in handy: 

  • only dispose of the parts of a plant that will regrow (for many species this is just the fruit and seeds, and the roots, but on some plants can grow new roots, so you need to know which species you're dealing with);
  • hang parts of the weed that won't resprout on a branch or in a tree fork to rot down and return to the soil; 
  • compost on-site in an old drum or other receptacle, usually with its base open to the ground;
  • create a raised 'raft' of dead branches or other material on which weeds (excluding the propagules) can be placed to decompose over time.
One way of dealing with green waste is to compost it on-site. This works well if you have plenty of space, can prevent propagules (the bits that will regrow!) from spreading from the composting bin or bay, and are prepared to deal with some follow-up regrowth. Does not work for air-borne seeds. 

Bagging up propagules to take them off-site can keep down the volume of green matter you need to move, but in large areas can still result in 'three bags full' - or more - depending on the type of weeds you are tackling. This weeding group in the Wollongong LGA is lucky enough to have volunteers donating space in their green bins.

Are you composting or otherwise dealing with weeds yourself? Making weed tea in your back garden, or using bokashi bins to ferment your weeds? If so, please share your tips and tricks, here or via Growing Illawarra Natives on Facebook

No comments

Post a Comment