All about Giant hogweed
On this page we tell you why Giant hogweed is not to be ignored! Find out how to identify it through the seasons, and how to get rid of this invasive, toxic plant.
What is Giant hogweed?
Giant hogweed (Heracleum\ mantegazzianum) is a highly invasive plant (part of the carrot family) that grows to impressive heights. The plant is identified by its tall, purple-blotched, bristly stems, large, jagged leaves, and huge umbrella-shaped clusters of white flowers.
Giant hogweed is a biennial or perennial herbaceous plant that can grow up to 5 metres in height. Flowering does not occur until the second or third year, or longer if conditions are unfavourable, but when it does, the white flowers look like very large cow parsley, with a pale, swollen rootstock. It produces 20-50,000 viable seeds a year, which are penny sized and paper thin and germinate quickly.
Giant Hogweed is a highly toxic plant that causes severe skin burns and scarring. Its sap can react to sunlight and lead to long-term injuries – especially dangerous on sites with public access, residential gardens, or active construction zones.
Under the Wildlife and Countryside Act 1981, landowners must prevent its spread. That means if it’s on your land – it’s your legal problem to solve.
What does Giant hogweed look like?
Giant hogweed can be identified by a number of key characteristics:
- Hollow stems
- Hairs on the stems
- Stems grow to 5-10 cm diameter
- Stems have purple speckling on
- Large spiky leaves up to 1 metre across
- Flower umbrells can be 80 cm across and grow from a central stem
- Flower heads first appear as a closed pod which unfurls to reveal clusters of small cream-white flowers
- Seeds are small, paper like texture with dark stripes
Giant hogweed in spring
In the spring, giant hogweed emerges as dark green shoots with spiky, lobed leaves, sometimes reaching up to 50cm tall, and has thin stems that will develop purple blotches and stiff, white hairs as the season progresses. The plant appears as a large, rhubarb-like rosette, before growing taller and developing the characteristic large, umbrella-shaped flower heads in the summer. Its key characteristics in summer are:
- Leaves: dark green and spiky with a jagged, lobed shape, similar to a rhubarb leaf with hairy underside. Young leaves can be up to 50cm tall initially, and they grow to be very large with time.
- Stems: hollow, green, and often develop purple blotches, covered in stiff, white, bristly hairs. They can grow up to 10cm in diameter on mature plants.
Giant hogweed in summer
- Size: It is significantly larger than other similar plants like common hogweed or cow parsley.
- Flower heads: The spring buds have opened up to reveal large flower heads made up of cluster heads of creamy white flowers.
- Stems: The purple/red blotches and thick hairs on the stems are a key indicator that distinguish it from other plants like cow parsley, which has a solid green stem.
Giant hogweed in winter
In winter, giant hogweed is a dead plant, with the large, hollow stems and the remnants of the flower heads being the most visible signs, while the leaves have withered and fallen. The tall, dead stalks are often still standing and may have dried, umbrella-shaped seed heads at the top. The plant is dormant during this time, with the roots in the soil, and the above-ground growth from the previous season has died back. Its key characteristics in summer are:
- Stems: that are hollow, and have a ribbed appearance. They can remain standing through winter and may show remnants of the purple blotches from the summer months.
- Seed heads: its flower heads have turned into dried seed clusters at the top of (now) brown stalks.
- Dead leaves: The large, spiky green leaves of summer can often be seen as a rosette of grey, dead leaves at the base of the plant.
MORE IMAGES OF WHAT GIANT HOGWEED LOOKS LIKE
HOW TO GET RID OF GIANT HOGWEED
Giant hogweed can present a real problem to landowners. Due to its tenacity, hogweed is able to grow in fairly inhospitable environments such as roads, railways, derelict land and rubbish tips. From an environmental perspective, hogweed creates a dense canopy that can out-compete native species, cause stream bank erosion and generally harm biodiversity. But it can pose a risk to humans and wildlife, too. It’s extremely toxic and can cause skin blistering if people come into contact with it.
If you’ve got Giant hogweed on your land, Environment Controls can help! We offer a range of services to identify, eradicate and remove Giant hogweed infestations on your property including:
- Herbicide treatment
- Complete excavation
- Mechanical control measures
Is Giant hogweed toxic?
In a nutshell – yes! All parts of this plant are poisonous. Its sap contains chemicals called furanocoumarins that cause a severe skin reaction known as phytophotodermatitis when exposed to sunlight. This can result in painful rashes, blisters, and burns, and can lead to scars or dark spots that remain for years. In some cases it has even lead to blindness.
If you come into contact with it, immediately wash the affected area with soap and water, keep it covered, and seek medical advice.
For these reasons we recommend contacting us for professional help with treatment control or complete removal.
GET RID OF GIANT HOGWEED
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