Invasive Non-native Species week (postponed)

INNS or Invasive Non-native Species are in normal times what we on the NNRs spend, probably more time dealing with, than any other problem. This week May 18th-24th was supposed to be INNS week but due to an unforeseen virus outbreak, had to be postponed. However we thought it was worthwhile to mark the occasion by writing about one of the better known species.

While most of there are a greater variety of INNS at Loch Lomond NNR., Flanders Moss is not immune Rhododendron, Yellow Azalea, Labrador Tea, Sitka Spruce, Lodgepole Pine and Western Hemlock.

Blawhorn Moss is fairly free of INNS; just the occasional Sitka Spruce.

The list of INNS at Loch Lomond is huge. The Reserve is at the end of the Endrick and Blane catchments where it meets Loch Lomond. Anything and everything ends up on the Reserve.

In no particular order the following INNS


Few Flowered Leek Allium paradoxum

American Skunk Cabbage Lysichition amercanus

Giant Hogweed Heracleum mantegazzianum

Himalayan Balsam Impatiens glandulifera

Bamboo Salsa palamata

Rhododendron Rhododendron ponticum

Japanese Knotweed Fallopia japonica

Himalayan Knotweed Polygonum polystachyum

Flowering Rush Butomus umbellatus

Pick a back Plant Tolmea menszii

Monkey Flower Mimulus guttatus

New Zealand Pygmy-weed Crassula helmsii

Canadian Pondweed Elodea canadensis

Nuttalls Pondweed Elodea nuttallii

And that’s just the flora, we also have fauna

American Mink Neovison vison

Fallow Deer Dama dama

Canada Geese Branta Canadensis

And others that haven’t arrived or we haven’t found yet.

Not all of these we control, some e.g. American Mink are managed solely by the landowners and Canada Geese aren’t managed at all. The two pond weeds Canadian and Nuttalls aren’t managed either, mostly because there isn’t any practical way of going about it. Fully aquatic species are the most difficult to deal with as they operate in an environment that’s way outside the comfort zone of the average human.

Giant Hogweed


Giant Hogweed

One of the best known and spectacular of the INNS is Giant Hogweed, native to the Caucasus.  It was introduced to Britain in the 1820 and it’s the biggest by far of the umbellifers growing up to 5 metres in height.

It can form dense forests and each plant has the capacity to produce 40,000+ seeds. Giant Hogweed is one of the high priority INNS at Loch Lomond NNR.


Giant Hogweed Distribution (BSBI Plant atlas)

As well as swamping all over vegetation GH has quite literally a sting. The sap of Giant Hogweed causes phytophotodermatitis in humans, resulting in blisters, long-lasting scars, and if it comes in contact with eyes, blindness


Giant Hogweed forest With Himalayan Balsam understory

About the only plant that isn’t swamped by Giant Hogweed, is another INNS on at the top of our hit list; Himalayan Balsam.

The Giant Hogweed just makes it nearly impossible to get at the Himalayan Balsam, without wearing uncomfortable amounts of PPE.

At the Reserve, we worked out fairly early on that one of the most effective ways of dealing with Giant Hogweed is grazing with livestock,  especially sheep (although cattle will also eat the plant). Although the sap is full of nasties, it doesn’t affect sheep or cows. One of the reasons for introducing Giant Hogweed in the first place was as a fodder plant but it fell out of favour with dairy cattle, because it gave the milk (and subsequent butter and cheese) a bitter taste.


Sheep grazing Giant Hogweed

The method is and remains very effective, but there are parts of the NNR that are inaccessible to livestock, and for these areas a different approach is required.

In late May/early June; before the plant reaches full size, the technique is to cut the stem about 10 centimetres below the surface, using a long handled spade, to reduce the risk of coming into contact with the plant.

Timing is everything. The trick is to catch the plant just before it flowers/seeds. Although Giant Hogweed is a perennial once the plant seeds it dies back. So clobbering it in a flowering year finishes the plant permanently

It’s unusual and agreeable to find a method which is easy and effective when dealing with INNS. The combination of livestock grazing and “spading” has reduced the giant Hogweed population on the reserve to zero, without any recourse to chemical treatments.

As with all INNS. The key to controlling them, is a detailed understanding of the life cycle and ecology of the target species. In other words “know thine INNS”.


Extract from 2019 Loch Lomond NNR INNS Report

However there are large forests of Giant Hogweed less than one kilometre up river of the NNR. So constant monitoring is required to keep the total at zero, or thereabouts.

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