You may have noticed a tall, thick-stemmed plant with large clusters of white flowers, rather like oversized cow parsley, while out on walks over the past few weeks. If so, it could be Giant Hogweed, a very dangerous invasive plant that has enjoyed a particularly fruitful summer which has aided its spread.
Imported to the UK from Central Asia as an ornamental plant in the 19th century, Giant Hogweed can now be found throughout the UK. When fully grown it can reach up to 5 metres in height, with thick green stems covered in purple blotches and stiff white hairs.
The sap of Giant Hogweed contains furocoumarin which removes our skin’s ability to protect itself from sunlight. If the sap gets on your skin, it can blister badly, recurring for several months and even years. If this happens, be sure to wash the area immediately and seek medical advice.
Being seed-based, control of Giant Hogweed is usually achieved with herbicide applied over three years or more, the aim being to gradually deplete the soil’s seed bank.
Not dangerous to human health but equally difficult to treat is Horsetail, an aggressive, persistent weed with a root system that can extend over 2 metres in depth. Like Japanese knotweed, new plants can regrow from any small piece of rhizome left behind in the soil. Upright, miniature fir tree-like shoots appear in early summer which grow into a dense foliage of leaves covered in a waxy coating. Horsetail can be physically excavated or treated with herbicide but we always mix ours with an adjuvant which helps break down the coating and usually controls the plant within 2 to 3 years.
We deal with all kinds of invasive plants and something they all have in common is that they’re best tackled early. So if you’re not sure what you’re dealing with, give us a call or email a photo to firstname.lastname@example.org.