Good Weed, Bad Weed?

Words can be very powerful and conjure-up strong emotive reactions. If we describe something as ‘weedy’ it’s usually a negative term suggesting something defective or weak etc, but nothing could be further from the truth as far as actual weeds are concerned! Most weeds (lets assume a working definition as ‘wrong plant in the wrong place at the wrong time’) are part of our natural flora and can compete very effectively for light/water and produce lots of flowers (nectar)/seeds to ensure their survival.

Even the ideal gardens include weeds!

Gardeners are being encouraged more-and-more to embrace these humble itinerants and create wild places or to forego mowing the lawn for a month (Plantlife campaign) to maximise opportunities for invertebrates and all the birds and animals that depend on them for their own welfare. Attitudes are changing to what the ‘ideal garden’ looks like and it includes weeds! Outside the garden, weeds are not weeds at all; they are ‘ecosystem service providers’!

So, what about non-native invasive weeds?

Should we re-visit our attitudes and responses to the presence of these foreign colonisers? This is certainly something worth discussing and our view is that the ‘right response’ to plants listed under the Wildlife and Countryside Act Section 14/Schedule 9, is dependent on a careful assessment of site-specific factors. Put simply, the Act requires that non-native and ‘invasive’ plants should never be planted and, if already present, need to be controlled to prevent further spread to ‘the wild’.

Risk assessment factors for invasive weed experts

What does this mean if we find Cotoneaster (C. horizontalis) growing in an urban planting scheme? It may be the only plant in the area and a nesting site for sparrows in summer/feeding ground for blackbirds in the winter. Himalayan Balsam is often viewed as being a ‘good’ source of nectar for insects/pollinators and is late flowering (when other native species have already started dying back) but does that mean we should leave it alone and accept it’s increasing dominance of riparian habitats (to the detriment of native species)? The answers to these questions are never simply ‘yes’ or ‘no’…

Every invasive species should be considered a threat

Each and every invasive species should be considered on a site-by-site basis as more or less of a threat to the local ecosystem (or more-or-less likely to cause a nuisance in a neighbours’ garden!) and there are a number (up to a dozen or so) of risk assessment factors that can help guide invasive weed experts (who understand the features/characteristics of each plant) towards a recommendation for their client. The PCA are developing a tool to make this process as objective as possible and give the sector a consistent approach.

A flexible, analytical approach wins the day

How does this affect our approach to Japanese knotweed or Giant hogweed (the species for which advice is most commonly sought)? In both cases there are strong ‘risk factors’ that almost always lead to a recommendation for treatment or removal e.g. structural impacts or health hazards. Add to that the fact that both are exceedingly difficult to ‘control’ (i.e. prevent spreading to the wild) and may fall under other legislation (‘nuisance’) and you soon realise that our multi-factorial approach doesn’t necessarily change the status quo in respect of typical response scenarios for these particular species. But as we broaden our horizons to encompass all 39 invasive weeds which fall under the ‘Act’, the PCA believes a flexible, analytical approach will produce outcomes that are compliant with the law but also ‘best for the client and the wider environment.

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