Is Japanese Knotweed Poisonous?
Is Japanese knotweed poisonous? There are many plant species in the UK that are harmful to humans and animals. Stay safe – find out more now.
Japanese knotweed and other fast-growing invasive species cause numerous problems for the native British landscape. Many of these are harmful to humans and animals, but even non-poisonous plants can be troublesome.
Is Japanese knotweed poisonous to humans?
Japanese knotweed is not poisonous to humans. In fact, it is edible. Certain parts of the weed can be cooked like rhubarb or used as a vegetable substitute. Its taste is described as being slightly sweeter than rhubarb.
It is not recommended you eat the weed raw, as some reports claim the weed can cause irritation to sensitive skin.
The risk with Japanese knotweed comes with its ability to grow from even the smallest piece of stem. Having evolved on the harsh conditions of the sides of volcanoes in Japan, its growth rate is legendary. In summer months the plant can grow up to 10cm a day, reaching a height of around 7 metres. Not only can it damage and destroy hard surfaces, such as tarmac, concrete and brick walls, the plant grows so quickly and spreads so easily, it can deprive native plants of nutrients and sunlight, causing them to die.
Touching Japanese knotweed is not advised under any circumstances, as this can contribute to the spread of the weed. If you have Japanese knotweed on your property and you allow it to spread to a neighbours land, you can face fines of up to £2,500.
Is Japanese knotweed poisonous to livestock?
Your livestock can also safely eat Japanese knotweed. Many reports indicate horses, cows, and goats will readily eat the broad leaves when available without adverse effects.
Is Japanese knotweed poisonous to dogs and cats?
Dogs and cats have different digestive systems to those of humans and standard livestock animals. Reports vary as to the effects of Japanese knotweed consumption on dogs and cats, with some owners claiming the knotweed has harmed their pet and others saying the knotweed has actually improved their health.
More research is required to validate the effects of knotweed consumption on dogs and cats. In the meantime, it is advised you do not let your pets consume the weed.
If Japanese knotweed isn’t poisonous, then why is it a problem?
Japanese knotweed is the UK’s most aggressive invasive weed. Left untreated, it will spread and spread. It is a criminal offence to allow the weed to spread from your land to a neighbouring property.
Japanese knotweed shoots can grow up to 3 metres high through your plumbing, building foundations, and driveways. It outcompetes native vegetation and can also lead to erosion, causing longterm flooding issues.
How can Japanese knotweed affect you?
Repair work for damage caused by Japanese knotweed can range into the thousands.
Your mortgage and house price can also suffer. Legally, Japanese knotweed must be disclosed to buyers and banks. Many lenders have been reluctant to approve mortgages on properties with a history of knotweed.
The Wildlife and Countryside Act prohibits planting Japanese knotweed or disposing of cuttings in an irresponsible manner that might let it grow back. (And it will grow back, from cuttings as small as 2mm.) This makes home treatment almost impossible without risk of costly fines and criminal action.
Other toxic species
Other toxic species can be harmful to humans and domestic and livestock animals. Some of these are highly dangerous.
Is giant hogweed poisonous?
Giant hogweed (Heracleum mantegazzianum) is a very dangerous plant. Also known as giant cow parsnip or cartwheel flower, giant hogweed is toxic to both humans and animals. In July 2015, two boys were hospitalised after they touched the plant at a country park in Bolton.
Skin contact can cause blistering and a reaction similar to a severe sunburn. It can scar the skin and can even cause blindness if the sap gets in your eyes. Giant hogweed is green with dark purple spots and spiky hairs. The stalks are hollow and can grow up to 5 metres tall.
Is ragwort poisonous?
Ragwort (Jacobaea vulgaris) is classified as an injurious weed under the Weeds Act of 1959. Ragwort is poisonous to livestock; horses, donkeys, and other mammals will suffer fatal liver damage if they ingest it.
Ragwort is a tough, upright plant with a red tinge on its base. It typically turns greener and branches off towards the middle of the stalk.
Is hemlock water dropwort poisonous?
Hemlock water dropwort (Oenanthe crocata) is another plant harmful to animals. It is particularly dangerous because it can resemble one of several non-toxic plants. However, the roots are very toxic if eaten, and can lead to animal death.
Hemlock water dropwort is most toxic in early spring and late winter: leaves looks similar to celery and stay green all winter. In June and July, the plant then produces small pale pink and white flowers.