March 18, 2024

Who are the 'Dirty Dozen'?

Wilding conifers (10 species) alters our landscape, takes up large amounts of water from the water table and prevents regeneration of native species.

Buddleia forms dense stands in wide range of habitats. In riverbeds it can alter water flow, causing silt build-up and flooding.

Woolly nightshade produces toxins that poison the soil and inhibits regeneration.

Darwin's barberry replaces shrubland and regenerating forest.

Wild ginger grows from rhizomes. Dense beds replace all other species, and are shallow rooted, so when they become heavy with rain they can slip on steep sites and streambanks, causing erosion.

English ivy is a both a ground cover and climbing vine. It smothers and kills all plants from ground level to canopy, and prevents the establishment of native plant seedlings.

Wandering willie is also a ground cover. Like ivy it smothers the ground, preventing native seedlings from establishing.

Climbing asparagus smothers forest floor and understorey to 4 m, preventing the establishment of native plant seedlings and growth of established species. It can ringbark and kill soft-barked shrubs and trees.

Old man's beard smothers and kills all plants to the highest canopy, and prevents the establishment of native plant seedlings.

Moth plant germinates inside established forest, and smothers and kills plants up into the canopy, preventing the establishment of native plant species.

Banana passionfruit (4 species) smothers canopy, preventing recruitment.

Japanese honeysuckle climbs over and smothers most plants from ground to medium canopy. It can cause canopy collapse and subsequent invasion of grasses or ground vines.

Spartina (2 species) is a grass species found in the inter-tidal zone. It traps sediment, raising the level of the ground above the high tide mark and destroying the inter-tidal zone and habitat. It can reduce large estuaries and shallow harbours to thin drains surrounded by rough pasture, resulting in an immense loss of biodiversity.

Also see the project check list at

Posted on March 18, 2024 01:54 AM by murray_dawson murray_dawson | 0 comments | Leave a comment

April 11, 2018

Dirty Dozen has done its dash

The 2016 and 2017 Dirty Dozen competitions were a great success in raising awareness of plant pests, and this iNaturalist NZ project provided an ideal way for people to join the competition through posting their observations of the 13 (baker's dozen) weed species targeted.

DOC are not currently promoting the Dirty Dozen initiative, but their War on Weeds work remains alive and well. We will keep this project running, as it may still be of interest. Here are links to some past publicity:

Posted on April 11, 2018 09:46 AM by murray_dawson murray_dawson | 0 comments | Leave a comment

May 19, 2017

There's a bounty out for the Dirty Dozen!

Are you harboring wanted fugitives?
The Dirty Dozen are running wild and could be hiding in your backyard.
Learn to recognize the Dirty Dozen common weed species and act now to control them!

Make an observation of a Dirty Dozen species before August 30th 2017 to be into win the bounty!

See the website for more details

Posted on May 19, 2017 02:42 AM by ranger_dan ranger_dan | 1 comment | Leave a comment

September 26, 2016

The Dirty Dozen competition

Although the 2016 competition has now closed, we're still on the lookout for Dirty Dozen observations.

Thanks to all who took part by uploading observations leading up to and during Conservation Week. Congratulations to those who have been randomly selected as spot prize winners.

Posted on September 26, 2016 12:01 AM by murray_dawson murray_dawson | 2 comments | Leave a comment

August 18, 2016

Dirty Dozen Competition has launched!

As part of Conservation Week 2016 (10–18 September 2016) DOC is running a Dirty Dozen Competition. Load one or more observations of Dirty Dozen weeds to this project, before the end of 18 September, to be in the draw for cool prizes. Share the competition link with your friends. It's so easy to enter!

Posted on August 18, 2016 10:59 PM by murray_dawson murray_dawson | 1 comment | Leave a comment