Saturday, 11 April 2020

P is for Pirri-pirri bur

Please remember! We ask that people do not visit the Reserve particularly if you have to travel. All car parks on Holy Island are closed to visitors until government restrictions are lifted. Many residents on Holy island fall into the vulnerable category. Please adhere to these guidelines for the health and safety of yourself and others during this time.

Lindisfarne National Nature Reserve is a biodiverse hotspot for botany with nationally important plant species and even the endemic Lindisfarne Helleborine (Epipactis sancta). The Reserve is also host to a number of invasive species. Some are garden escapes that have found there way onto the Reserve through visitors or self-seeded from gardens in the area. One of the most prevalent of the invasive species is Pirri-pirri bur.

Pirri-pirri bur (Acaena novae-zelandiae) is an invasive species that is a low creeping plant that forms dense mats often crowding out native plants. It produces balls of reddish flowers which then ripen into barbed fruits with red hooks that that stick to legs and fur of passers-by enabling the spread of the plant. It is a New Zealand native that was first discovered on the Reserve in the 1930's. It is thought that the seeds of the first plants originated from sheep wool washings from the wool industry that occupied wool mills on the banks of the river Tweed. It quickly established itself within the dune system due to the plants ability to survive in the harsh conditions of the coastal areas of the Reserve. The plant can also survive trampling meaning that it became well established on the paths and desire lines. With the sticky seed heads, footfall through the dunes spread the plant readily.
Pirri-pirri burr seed heads eagerly waiting for a passer-by

On Lindisfarne National Nature Reserve a number methods of practical management of Pirri-Pirri have been undertaken over the years with much time and research being put in to come up with viable solutions. What makes the management of the plant extremely tricky is that the dune system contains many rare and specialist species so management has to be considered carefully to ensure that there is no adverse effects on other species. Currently during the summer the main paths and desire lines within the dune system are mowed and seed heads are balled up to stop the spread of the plant to other areas, not just on the Reserve, but other areas in Northumberland. Rotavating pathways where Pirri-pirri is dominant is another management technique. When done in the winter months this breaks up the leaves resulting in frost damage, killing the plant.
Balled up seed heads-this is what your feet can look like after a walk in the dunes!

Another method used is education of visitors. There are signs at every access point warning visitors of the presence of Pirri-pirri bur and encouraging people to check clothes and dogs for any burs and to remove them before leaving the Reserve.

Pirri-pirri bur is very well established within the dune system and will most likely never be completely removed as it is so entwined with other species. The good news is that since the year of its discovery it has not had outcompeted the dune plant assemblage that makes Lindisfarne National Nature Reserve so special and with current management techniques we can minimise the spread to wider sites.

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