The imposter invading the Water of Leith's banks
Invasive plants and their long-term risks to our beloved river
Edinburgh has burst into bloom; grey streets and dull empty parks are all but forgotten as we stroll through verdant tree-lined avenues in what seems like an endless spell of sunny weather.
The city’s waterways are busy with walkers, runners and cyclists enjoying the bursting green flora, the peace and tranquility and, now and then, the pungent scent of fresh wild garlic.
But appearances, as Aesop told us, can be deceiving. Is that white-flowered plant that may be lacking a few blooms really wild garlic? Or is it something more sinister? And how much can it really matter?
The truth is that, over the past decades, our beloved wild garlic has been usurped by a cunning imposter, posing as the real deal. To the untrained nose, this imposter smells just like wild garlic- but its narrow leaves and lack of petals give it away as the invasive “few flowered leek.”
Although relatively rare up until the 1960s, few flowered leek has spread so quickly across the UK that in 1981 it was added to the list of invasive species which are illegal to spread in the wild. This problem plant now affects large parts of the UK, but was first spotted very nearby. According to the Royal Botanical Society of Scotland, the first sighting of the enemy plant in the wild was made outside Edinburgh in 1863.
What’s the big problem?
Okay, so there’s a new garlicy plant in town- what’s the problem with that? Can’t the garlic and leek live harmoniously, side by side? While it seems a harmful triviality, invasive non-native species can have a significant negative impact on our ecosystems, particularly the Water of Leith.
This issue is that few flowered leek isn’t interested in being friends - this is really more of an invasion and occupation than a diplomatic visit. Out-competing not only wild garlic, but all other plants on the Water of Leith’s banks, this plant creates a monoculture- entire swathes of ground which would normally host a variety of plants is now covered in a dense mat of few flowered leek.
And as climate change scientist Sir David King warns us: “Invasive species are nature’s silent invaders, sneaking into new territories and wreaking havoc on the native flora and fauna. We must act swiftly and decisively to prevent further damage.”
Few flowered leek is not alone. Other non-native invasive species are swarming the river’s banks too. Himalayan balsam’s ability to spread seeds up to four metres away from the original plant has let it proliferate all over the Water of Leith, Corstorphine Hill, and beyond. That’s before you think about Giant Hogweed, Japanese Knotweed or Snowberry.
Besides upsetting the natural ecosystem of plants, animals and insects along the Water of Leith, invasive species can have dangerous impacts on the river itself. When these plants which dominate the riverbank finish flowering and die back for the rest of the year, they leave the riverbanks exposed. This exposed soil is washed into the river during rain, increasing the water level and therefore increasing the risk of flooding.
Edinburgh Council is already spending £750,000 each year on flood prevention - most of which is along the Water of Leith - as climate change will bring more and heavier rainfall to Edinburgh. The river itself is an outlet for excess water when the city’s drainage system overflows. This is why it is so vital to stop invasive plants on the riverbanks from making the flooding problem even worse.
Fancy picking some flowers?
There are ongoing efforts to route the invaders and return Edinburgh’s plant populations to their natural diversity.
In its most recent annual report, The Water of Leith Conservation Trust detailed some of the huge efforts it is making. Volunteers spent the bigger part of 8000 hours performing a whole range of tasks along the waterway and its banks, and included in that marathon effort were 62 different projects to detect and deal with invasive plants.
The Trust, alongside Edinburgh Council’s Grounds Maintenance teams deal with the nastier, tougher invaders. But Himalayan balsam and few flowered leek can be taken on by even the smallest of warriors. The Trust has had huge success working with school groups to pull up Himalayan balsam, for example. Thanks to the plant’s lack of bristles and thorns, a horde of hyperactive children can safely and constructively channel their desire to tear things apart. In fact, as the name suggests, Himalayan Balsam is actually very kind to the skin. Stick it in a blender and you’ve got a free hand lotion!
And what about Few Flower Leek? Considering it was originally brought here to be grown commercially, it makes sense to just eat the thing. All parts of the plant are healthy to eat (provided they are washed well and consider picking in spots away from paths and roads to gather them). Few flowered leek is still farmed as a vegetable and spice in its native Iran, and studies show it is rich in iron, manganese and antioxidants. Also, when chopped up and mixed with butter it can make a luminous green garlic bread, which is both delicious and comical. Be careful to know what you are looking for, however - few flowered leek has a similar appearance to a number of poisonous plants too.
So if you’ve run out of warm-weather activities and you’re not sure where to turn this weekend, perhaps a slightly destructive stroll along the Water of Leith is in order – or more advisedly if you’re unsure whether you’ll be pulling up the right thing, the Water of Leith Conservation Trust has some excellent volunteer events.
But let’s also remember that, while invasive plant species and exposed ground can contribute to river flooding, the much bigger culprit is human litter. Wet wipes that are flushed down toilets, plastic bottles tossed onto the path, wrappers which blow out of bins in the wind - these all end up clogging up the Water of Leith. So, if you’ are going to enjoy the Water of Leith this weekend, or to pull out a few invasive plants, make sure you don’t leave it messier than you found it.
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