If you think that weed control is purely seasonal – reading this article will change your mind.
It’s a mistaken opinion that weed infestations are best tackled during the spring, summer, and autumn seasons, either by treatments or via complete eradication. However, it may come as a surprise that some control projects can be undertaken throughout the year, and this is especially so with excavation methods.
A lot of the common problematic weeds have plant parts underground that lie dormant in certain months of the year, invisible but not harmless. They are simply storing their energy until their next season, when light and heat encourages growth above ground. The fact that some invasive species are not always visible is a huge issue for the construction industry and developers as the unseen enemy if disturbed during contractual works will cause projects to be put on hold until the infestation is resolved. So, if you don’t know it’s there, this can be a problem!
Let’s look closer at a few of the most common offenders:
Japanese knotweed
The obvious one is Japanese knotweed, which in winter the roots – known as Rhizomes (seen above) are not only deep underground but can remain capable of supporting life for up to 20 years. If the roots are fresh, they will snap easily like a carrot. The outside is dark brown, and the inside is orange/yellow in colour.
The root system can grow to depths of two meters and extend up to 7 metres horizontally from the visible part of the plant. These roots are what allows the knotweed to spread and are part of the reason that it is so resilient. It only takes a small amount of healthy root to give rise to an entirely new plant – and cause the infestation to re-emerge.
Common Ragwort
This species is so problematic it carries its own Government Code of Practice, being poisonous to livestock (and humans) if ingested. Ragwort is a biennial and is visible all year round due to the rosette which is a result of the seed bank from year 1, flowering only within it second year of growth.
Hemlock water dropwort
A native perennial growing to over a metre high in shallow water like streams, ditches, rivers and lakes, Hemlock Water Dropwort is the most toxic plant to both humans and animals growing in Britain. It is this tuberous root that can become exposed following flooding, dredging, dry summers causing bank erosion, the tuberous roots are sweet tasting (apparently) and becomes palatable to grazing animals. For amenity managers landowners and farmers with land used for grazing at certain times of year, it is of particular concern.
Parrot’s feather
Parrot’s feather is an emergent plant, which can be seen above the surface of the water as well as below it during the growing season. In winter the plant will die back and is only found in its submerged form. Parrot’s feather is highly invasive, it forms dense infestations in water, shading out other aquatic plants, causing flooding and damage to the invertebrate communities occupying the same ecosystem. It could be considered a threat to leisure activities such as angling and boating as well as causing issues with hydro-electric power stations, which would result in an economic impact.
Equisetum
Equisetum – commonly known as Horsetail is a “living fossil” that lies dormant over winter. This species derived from huge, tree-like plants that were prominent during the Paleozoic era, 400 million years ago – this is a species that knows how to evolve and adapt! A perennial plant, meaning it returns each year, it has hollow stems and shoots that look like mushrooms when they first appear. The plant’s stems and branches are formed from silica crystals which give it the feathery appearance. Despite its delicate nature this species knows how to cause damage, not just to structural elements such as paving, but its toxicity level is extremely high, and can be fatal if ingested by equines (hence the name).
The solution:
Only experts in this field can give you the peace of mind that no hidden enemy is lurking on your land or property. When it comes to certain species, that lie underground it pays to get a professional surveyor onsite who will know what to look for, even when it seems impossible! A trained surveyor will know where these roots live and be able to spot them even by a small fragment. Once identified, removal methods will be advised to completely eradicate the problem by carefully digging up every part of the plant and removing it to a licenced landfill site, leaving the land clean and fit for purpose again. In the case of Japanese knotweed this is usually excavation, however not one solution fits all – we keep an ‘integrated weed management’ approach front of mind when it comes to choosing the best method of control.
How do we know when the land is clear? When our expert field operatives and consultants are happy that not even the tiniest of fragments is left in the ground. This is not a job for the untrained!
