FAQ on Giant Hogweed

Answers to the most common Giant hogweed questions below

Giant Hogweed Questions and Answers

Below are some of the most commonly asked questions regarding Giant Hogweed. Click to reveal the answers.

Q1: What is Giant knotweed?

Q2: How is Giant hogweed controlled?

Q3: How to identify Giant hogweed?

Q4: How to remove Giant hogweed?

Q5: What is the difference between Hogweed and Giant hogweed?

Q6: Can Giant knotweed be removed?

Q7: Is Giant hogweed poisonous?

Q8: What kills Giant hogweed?

Q9: Is Giant hogweed dangerous?

Q10: Where can I report Giant hogweed?

Q11: How do I get rid of Giant knotweed?

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Q1: What is Giant knotweed?

Giant hogweed is a tall, majestic, invasive plant that is dangerous to humans. The plant, which is commonly found alongside rivers, contains toxic sap which can ultimately cause Lime disease. In severe cases, Giant hogweed can cause blindness. 
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Q2: How is  Giant hogweed controlled?

The 2 most common ways to control Giant hogweed is through the use of chemicals or excavation.

Spraying Giant hogweed with chemicals is an effective control and cost effective measure but can take several years to completely remove due to the number of seeds the plant produces.

Excavation is the quickest method to eradicate Giant hogweed, although it is a more expensive option.

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Q3: How to identify Giant hogweed?

Here are some common characteristics of Giant hogweed:

  • A dark red/purple stem with spotted leaf stalks
  • Leaf stalks are hollow and produce sturdy bristles
  • Umbrella-like white flowers held in a flat-topped cluster all facing upwards
  • Width of leaves can reach 5 feet

Q4: How do I remove Giant hogweed?

Giant hogweed removal is achieved either through the use of chemical spraying or excavation. Attempting to chop down a Giant hogweed plant will just send up a new growth and possibly expose you to toxic sap.

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Q5: what is the Difference between Hogweed and Giant hogweed?

The difference between Giant hogweed and hogweed (common hogweed) can be seen within the leaves, stems and size of the plant.

Giant hogweed usually grows to at least 4 metres tall before flowering. Common hogweed will begin flowering around 2 metres. 
Giant hogweed will contain around 50 or more flower stems on each flower umbel. Whereas common hogweed will normally have around 20 stems.

The stem of Giant hogweed is typically smooth, can reach 5 inches in diameter and usually develops purple blotches. The stem of a common hogweed plant is generally hairy and only reach a couple inches in diameter. 

Furthermore, common hogweed can grow almost anywhere but prefers riversides and roadsides. Giant hogweed, however, is almost exclusively found by a riverside only. 

A good tell-tale sign is if the stem is over 2 metres tall, then it is most likely Giant hogweed.

Q6: how is Giant knotweed removed?

Giant hogweed can be removed by spraying the plant with chemicals. Although this is a cost-effective Giant hogweed treatment plan, it can take several years to be effective, given the large number of seeds this plant produces. A more expensive option which will remove the Giant hogweed straight away is removal through excavation.

Q7: Is Giant hogweed poisonous?

No. However, the plant contains a phototoxic sap which can cause painful blisters and skin irritation. In more severe cases it can cause blindness.

Q8: What kills Giant hogweed?

Killing Giant hogweed requires several years of chemical spraying or excavation. Preventing the seeds from spreading each year is key to completely eradicating a Giant hogweed problem.

Q9: Is Giant hogweed dangerous?

Yes. Giant hogweed contains toxic components within its leaves, stems, flowers roots, and seeds. Even the slightest brush against a Giant hogweed plant can transfer the toxicity to your skin.

Q10: Where to report Giant hogweed?

You can report any sightings of Giant hogweed to SEPA (Scottish Environmental Protection Agency) whose main role is to protect and improve the environment.

Q11: How do I get rid of Giant knotweed?

A Giant hogweed treatment plan will need to be put in place. The 2 options are to either use chemical spraying over a number of years or excavate it from the ground. Chemical spraying is typically the removal option chosen for Giant hogweed as it can be more cost-effective than excavation.

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