Casual Gardener: Weeding out the worst offenders

Is the use of weedkiller excusable in certain circumstances?

Giant Hogweed can grow to five metres and contains dangerous sap
Giant Hogweed can grow to five metres and contains dangerous sap

This column has long been a supporter of the assertion that ‘a weed is just a plant in the wrong place’, however, it does require some qualification.

In the eye of the beholder, any plant can be regarded as attractive, though usually it’s about context. For example, on a countryside verge, willowherb, dandelions and buttercups are all acceptable and should be tolerated, even celebrated. Yet any of the above growing in your beds and borders would likely be met with disappointment.

There’s also a hierarchy of weeds, with benign native wildflowers at the bottom and pernicious, invasive aliens at the other end of the scale. The former can easily be described as simply a plant in the wrong place whereas the latter are potentially harmful both to humans and indigenous flora.

It was an email last week from a reader of this column that got me thinking about weeds and how to deal with them. The interloper in question on this occasion was mare’s tail – also called horsetail – an invasive, deep-rooted perennial that spreads quickly to form a dense carpet of fern-like foliage, crowding out less vigorous plants.

My own garden is thankfully free of Equisetum arvense but I know how rampant it can be, emerging from tarmac in some instances and seemingly resistant to all organic controls with roots as deep as 2m (7ft), making them hard to remove by digging out.

Blooming Sakhalin Knotweed or Fallopia sachalinensis in autumn
Japanese knotweed was introduced to Ireland as an ornamental

The only solution I could reluctantly recommend was a dousing with glyphosate or some such herbicide. Either that or call ‘the professionals’, who’d likely douse it with glyphosate and charge handsomely for the pleasure.

My reservations around glyphosate (the key ingredient in commercial herbicides like Bayer’s Round-Up) are its impact on the environment and on human health. Over the past decade there’s been a steady albeit too slow decline in the use of weedkillers across Europe.

More recently government departments and local authorities in the north have copped on that they can boast a ‘win-win’ by saving money and helping biodiversity – including my own Newry, Mourne and Down Council.

While I’m vehemently opposed to using weedkillers simply for cosmetic reasons, which I surmise is around 90% of applications, I appreciate there are perhaps circumstances when their use becomes necessary.

Earlier this month, councillors in Newry, Mourne and Down reversed a previous policy of glyphosate reduction in order to combat the spread of giant hogweed and Japanese knotweed at Newry’s new city centre park around the Albert Basin.

It’s arguable whether in these circumstances a chemical solution is the most effective against these two notorious pernicious weeds, both of which were introduced to Ireland more than a century ago as ornamentals. Weedkiller in isolation is never a sustainable solution.

Giant hogweed is what it says on the tin – a giant hogweed – which has/had huge appeal as a towering, architectural plant that particularly likes a pond or riverside. The downside is the stinging-to-touch sap in its thick stalks, which would’ve once appealed to adventurous children.

Japanese knotweed, on the other hand, has no redeeming features yet is a stubbornly invasive plant.

Regrettably, there are circumstances when the use of glyphosate has to be weighed up against the spread of a what are universally recognised as ‘weeds’ - rather than just plants in the wrong place.