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Stopping Invasive Weeds Spreading

One of the key considerations for effective invasive weed management is to prevent the spread of ‘propagules’.  This is a general term to describe all parts of a plant which can re-generate to produce new plants and includes fruit/seeds, bulbs, corms, tubers, rhizomes, stolons and so on.  

In the case of some plants, even above ground parts of stems/shoots can retain the ability to grow new roots and establish in soil remote from the parent plant.  These matters have regulatory significance in that the Environmental Protection Act deems soil (and other waste) containing viable propagules of invasive non-native plant species to be Controlled waste which must be disposed of in accordance with the ‘duty of care’ set out in section 34 of the Act. 

Establishing the risk of invasive weeds spreading

Because of the wide range of propagules, for each invasive plant species it is important to establish where the risk (of spread) lies.  

For invasive plants which spread through wind dispersed seeds we can try to manage the risk by stopping flowering/seed development processes altogether.  But seeds persist in the soil too and can survive for long periods, especially if the soil is subject to disturbance and the seeds get buried.  

The so-called seed-bank can be exhausted over time with various low-impact interventions, but the risk of re-colonisation never goes away completely (new seed imports from surrounding area). But potentially, if time is available, the waste generated is zero (no need to remove soil from the location).

Giant Hogweed - in the park - PCA

What if propagules are in the soil already?

But what about situations where the propagules are largely in the soil and may survive burial or other challenges via periods of dormancy lasting decades (e.g. Japanese knotweed, Giant rhubarb)?  

Or the site is due for development and the extent of invasive weed distribution means that medium to long-term management is not a viable option?  Here the normal solution is to consider some degree of excavation of contaminated soils. This clearly creates a waste management ‘duty-of-care’.  

Various strategies can be deployed to manage such excavation projects (to control waste volumes generated) and actual waste leaving site may be reduced further by careful monitoring of the dig and/or some soil sifting/screening (this latter only if the screened soil can be re-used on site, something a qualified invasive weed specialist can advise on).

Some professional guidance on waste control

The PCA has produced a number of resources to help professionals understand the intricacies of the Waste Regulations in the specific context of invasive weed management as well as some general advice on safe site management during excavations. Check out the document below.

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Helpful Invasive Weeds Videos

Want to learn more about invasive plants?

For those interested in learning more about invasive plants & weeds, there is a variety of PCA training options for surveying professionals as well as technical/trade professionals that includes our Invasive Plant iD Course

Use the search tool below to find available timber preservaton related training courses or simply go to our training & qualifications section.  Alternatively, if you want to chat to someone, contract our training team on 01480 400 000 or contact them online.

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