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8:54 AM 15th July 2020

Public Asked To Help Monitor Alien Invasion

The general public is being asked to keep alert against an alien invasion that blights Nidderdale Area of Outstanding Natural Beauty.

Himalayan balsam - credit Elizabeth Bishop
Himalayan balsam - credit Elizabeth Bishop
The offending non-native plant, Himalayan balsam, has a known impact on the health of riverbanks and wildlife. A recurring problem, the invading plant is persistent thanks to its explosive seed heads, which spread very easily. The prime-time to try and control the invasive growth is July and August.

The invasive growth overshadows natural plant species, which impacts on bio-diversity and river health. It causes widespread erosion of river and canal banks leading to flooding and the suffocation of fish eggs.

Iain Mann, AONB Manager, said:
“At Nidderdale AONB, we have a dedicated team of consultants, contractors and volunteers surveying and removing the offending plant. Himalayan balsam is a very persistent plant and creeps back. The general public, walkers and landowners can help us by keeping an eye out for it and reporting it to a national database.”

The public can record the presence of Himalayan balsam on a national database by going online via PlantTracker, which can also be downloaded as an App, or via the Non-native Species Secretariat website.

Although the public are also asked to remove the plant on their own property if they can, if the seeds have already developed trying to pull the plant has no benefit and can even spread it to new locations.

Iain added:
“It’s best the removal is left to trained contractors and volunteers, as Himalayan balsam can grow on steep drops on the water’s edge, and it’s important not to trespass too on any private lands. Even if you’re unsure on identifying and removing the plant, you can still take action by reporting its location on a national database. The best thing then is to help raise awareness of what the plant looks like so more people can help identify it. The Nidderdale AONB website has a handy guide to identifying Himalayan balsam throughout the year.”

The team is working specifically on three headwater river waterbodies in Upper Nidderdale, including a reservoir designated as a Site of Special Scientific Interest, to survey and remove Himalayan balsam as part of its ‘Headwaters for Healthy Rivers’ project, funded by an EU Water Environment Grant.

Iain said:
“It may just seem like a plant but biosecurity is important to protect against the invasion and needs to be taken seriously. Flood risks and infrastructure damage of rivers can have a big financial and social impact.”

Fact Box:
About: Himalayan balsam is from the Himalayas and was introduced to the UK in 1839. It now an invasive weed of riverbanks and ditches, where it prevents native species from growing which also then impacts upon insects and other mini-beasts. It is fast-growing and spreads quickly, invading wet habitat at the expense of other, native flowers. Because the plant is an annual it puts all its energy into producing around 800 seeds which it expels up to 7m using its explosive seed pods, this can send the seeds into the river, causing further dispersal downstream.

Height: up to 2m

When to see: May to October

Our largest annual plant, it flowers from mid-June to October.

How to identify:
Himalayan balsam has large, pink flowers shaped like a bonnet; these are followed by hanging, green seed pods. The stems are a green to red early in the year, turning pink to red in summer and are easy to snap as they are hollow. The leaves have a fine serrated edge.


Himalayan balsam - credit Elizabeth Bishop
Himalayan balsam - credit Elizabeth Bishop
How to remove from your property (do not remove elsewhere without the landowner’s permission):
It is simple and easy to remove the plant by hand, pull the shallow rooted plants out completely and break the stem to prevent regrowth and seed production.

If the flowers have already made seed heads which can be the case from mid- August – extra care needs to be taken pulling up the plants so the seeds are not dispersed. Carefully place a bag over the flowers and seed heads to capture them and then remove the plant. Any seeds removed must be disposed of carefully. They cannot be put in your bin, including one for garden waste, or compost heap.

Do not transport the dead plant, just leave it in situ to help to minimise the contact between the pulled roots and the ground, as the balsam can re- sprout and grow

Take care not to take balsam seed or plant home on your boots and clothes – make sure you don’t spread it by accident.

Take care not to leave the pulled stems on footpaths which can be a slip hazard

It is advised to wear long trousers and sleeves when pulling up these plants as balsam tends to grow alongside stinging nettles and brambles.


https://nidderdaleaonb.org.uk/about-us/nidderdale-aonb-projects/headwater-for-healthy-rivers/