A towering invasive plant capable of reaching up to 15ft is returning across parts of the UK just as gardens are being cleared for spring – raising fresh warnings ahead of its peak growth in May.
Giant hogweed is re-emerging, and so are its dangerous effects, with its rapid seasonal surge expected to accelerate in the coming weeks.
Authorities have issued fresh warnings to highlight the plant’s toxic sap, which can cause severe skin burns when exposed to sunlight, warning that the combination of warmer weather and increased garden design work makes this period one of the highest-risk times of year.
Article continues belowWhy giant hogweed is growing now
Giant hogweed survives winter underground and begins regrowth in early spring. By April, new shoots emerge from long-established root systems and seed banks in the soil.
The RHS states that "in its early growth it can be confused with other plants like cow parsley and common hogweed."
Although plants are still relatively small at this stage, growth accelerates quickly as temperatures rise, as is the case with Japanese Knotweed too. By May, giant hogweed can grow rapidly and become highly visible in affected areas, particularly in undisturbed or overgrown areas.
Where in the UK homeowners are most at risk
The highest concentration of sightings is typically linked to river valleys and lowland waterways, where seeds are carried downstream and settle along banks before spreading outward.
In the UK, higher-risk areas include:
- River corridors across southern England, the Midlands and Wales
- Waterways running through urban areas such as London, Birmingham and Manchester
- Fringe countryside where gardens back onto railway embankments or unmanaged land
Gardens most at risk are usually those with direct boundaries onto rivers, canals or overgrown public land, where seeds can easily travel in from surrounding areas.
What giant hogweed warnings are being given for May
The Department for Environment, Food & Rural Affairs (DEFRA) advises homeowners that giant hogweed should be treated with caution during its peak growth.
The guidance warns that the plant’s toxic sap can cause severe skin burns if it comes into contact with skin exposed to sunlight, particularly during garden clearance, cutting or strimming, where accidental exposure is most likely.
It also advises that suspected plants should not be handled without protection, and that larger or established growth is typically best dealt with through professional removal, as improper cutting or disturbance can increase the risk of spread and exposure. Similar care and attention is required for Japanese knotweed removal too.
As cases of giant hogweed burns re-emerge, DEFRA says it is more important than ever to remain vigilant over giant hogweed, especially as the chances of encountering these dangerous plants grow.
