Pirri-pirri-bur (Acaena novae-zelandiae) originates from Australia and New Zealand, and most likely arrived in the Tweed catchment via seeds tangled in imported sheep’s wool. The wool was washed in the textile mills found along main rivers with populations of this plant establishing on the banks of the Tweed from the early 1900s onwards.
Pirri-pirri-bur is a short, evergreen creeping plant species which forms dense mats and grows to a height of around 2 to 15 cm. The small, shiny leaves are dark green with toothed edges arranged opposite one another. The ball-like heads are very distinctive and have many tiny white flowers in June and July. It’s probably most visible in the late summer and autumn, however, when it develops dark red, spiny seed heads.
Impacts
This species forms dense mats which smother native plants and produces hooked burs that catch onto clothing and animal fur and can easily be transported from site to site. Seeds from the burs have made their way to Lindisfarne National Nature Reserve; here this species is particularly damaging to the rare and sensitive flora there with reports of the plant impacting on ground-nesting birds.
Help us control this damaging invasive non-native plant species by sending in your sightings. If you think you’ve seen pirri-pirri-bur or need more information, please email us on info@tweedforum.org giving your name, contact number, the exact location of the plant and the date seen. Please include a photo of the plant if possible.
Pirri-pirri-bur control
This species is extremely difficult to control once established. There are a variety of methods which can be used to try and control this species, depending on the size of the site and the terrain:
1. Grazing – introducing livestock to infected areas can manage seed production.
2. Hand pulling – involves physically removing the plant by hand then disposing by incineration. Removal of the entire plant is required to ensure no regrowth the following season.
3. Seed collection – removal of the burs can limit the risk of the seeds being spread.
4. Chemical control – glyphosate control can be effective but will damage surrounding vegetation.
For a full list of tried and tested methods please visit www.pirripirriburmanagement.wordpress.com/control-methods/
