Turning nasty weeds into nutrient-rich compost

What is the deal with the big black bags popping up in parks and reserves in Pōneke?

A young man with blond hair and a yellow jacket holds open a large black bag as a woman wearing gloves, cap and rain jacket fills it with weeds. The pair are in a field of dry long grass and scrub. — Volunteers clearing weeds. Photo by Simon Kennett.

You may have noticed large black sacks sitting in sunny spots throughout Wellington’s green spaces. No, they are not illegal dumping or something sinister. The bags are specifically designed to break down weeds and create compost in six to 12 months!

These bags can be found in a variety of parks and reserves around Pōneke, including Mākara Peak, Skyline Reserve and Monaghan Road Reserve.

Wellington City Council Biosecurity Specialist Illona Keenan says Wellington has over 140 community groups that work in reserves and parks around Pōneke.

“These volunteers put in a lot of hard mahi, contributing to a variety of environmental causes including pulling Tradescantia and putting these soft weeds into the special bags for composting.”

Two large black bags, full with weeds, resting on grass beside flax plants on a sunny day.

Nature may not be tidy, but it is neat!

These weed bags help to reduce negative impacts. They reduce the need for herbicides and cut out the carbon emissions that would be used to transport the weeds for disposal.

The bags are also quite “satisfying to fill” according to Illona – which make sense given their enormous size of 1.8 x 2.4 metres.

“Another great benefit is in six to 12 months the weeds in this bag will transform into fantastically nutritious compost! Containing weeds like Tradescantia and transforming them into compost on-site is better for the ecosystem as the nutrients are returned to the soil where they came from,” Illona says.

Four volunteers in brightly-coloured raincoats stand in a field of long tangled dry grass and three large black bags which are filled with weeds. — Volunteers worked hard to fill the bags with Himalayan balsam before the rain got serious. Photo by Simon Kennett.

Do you have a backyard full of weeds?

If you aren’t sure how to deal with the weeds in your garden, Weedbusters has a list that tells you how you can manage them.

These bags are a fantastic option for seed-free soft weeds but they may not be the right fit for you. Once filled they are almost impossible to move and must be left in a sunny spot for six to 12 months.

The best way of disposing of your green waste is taking it to the Southern Landfill. For only $5 you can dispose of up to 85kgs of green waste which will then be used to make compost.

Disposing of large quantities roadside in rubbish collection bags is not the way to go. Council’s official yellow rubbish bags cannot contain more than 10 percent green waste. Disposing of green waste in the general landfill creates a lot of carbon emissions.

Other weed disposal options include hiring a mulcher, solarization, and at-home composting.

Weeding is a great way to get outside and do your bit for the environment. If you don’t have much backyard to tend to there are plenty of volunteer groups in Pōneke! Visit our website to see the various ways you can volunteer outdoors with Wellington City Council.

If you're keen on having your own big black bag to help combat the weeds in your garden, you can purchase them from the EcoMatters online store.