Giant hogweed

Heracleum mantegazzianum

Overview

Photo credit: ©GBNNSS

Heracleum mantegazzianum - Giant hogweed

Widely Spread Species:

Under Article 19 of Invasive Alien Species Regulation (1143/2014) Giant hogweed has been identified as a Widely Spread Species in Northern Ireland and as such, management measures will be put in place to minimise its impacts.

Habitat:

It is found in bogs, fens, grasslands, woodland, urban, agricultural and horticultural areas, and riparian zones.

Description:

It is a tall perennial herb (3-5m) with a pale yellow root
Its stem is hollow and is green with purple patches
The flowers are white and in umbels up to 80cm across
Its leaves are large (up to 2.5m across), and are in opposite pairs with a terminal leaf. It can produce up to 50,000 seeds per year
It usually produces seeds before dying each year

Download N.I.E.A. ID guide

Origin and Distribution:

Giant hogweed is native to Asia but is now invasive in North America, continental Europe, Great Britain and Northern Ireland.

Potential/Known impacts:

This species has a high competitive advantage over native plants
It can out compete for space and resources by shading out native and desirable plants
There is also a loss in invertebrate diversity as the plants these animals depend on become scarcer
Other impacts include a significant increase in riverbank erosion
In summer time rights of way and access points for water users such as fishermen may become impassable due to high infestation rates of giant hogweed
It is also harmful to human health as it produces sap that causes severe burns that will blister in the sun and continue to effect the skin for many years after an initial burn

How did it get here:

Initially the species was brought in as an ornamental plant of parks and gardens
Its seeds can travel on the wind and in water, meaning that it can travel relatively easily in the right conditions
It may be unintentionally spread further by though contaminated soil where seeds can lie dormant for 20 years

Is it found in Ireland or Northern Ireland?:

It is present and widespread across Northern Ireland.
More distribution information can be found at NBN Atlas NI.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.

Manual Method for prevention:

Hand cutting should never be undertaken unless the operator is wearing full protective clothing to prevent skin contamination by the sap.
Infestations need to be controlled by digging out the whole plant as cutting through the stem must be done below ground level to ensure damage to the rootstock and to prevent regrowth from the base.
This is known as 'tap rooting' (see images below)
Cut the taproot approximately six inches below ground level using a spade, shovel, or anything with a large sharp edge
In areas with erosion or on steep inclines (where additional soil may be covering the plant base), plants may need to be cut up to ten inches below the soil

When cutting the root you need to separate the thick stem base bearing old leaf scars from the root below
If possible (for your safety), cut the plants before the leaves are very large
The cut part of the plants should be removed from the soil and left out to dry (safest for control person) or bagged and disposed of
Survey the site for up to 7 years after the last growth as remaining seeds may be viable and regrow

Futher Resources:

More Methods to Prevent Spread

Promote native species and biodiversity - use alternative, native plants
Know what you are buying/growing and source native Irish seed and plants
Do not swap plants and cuttings
Follow control advice and watch out for hitchhikers - inspect new imported purchases for invasive pest and pathogens
Never collect plants from the wild
Safe disposal of plant material and growing media
Report all sightings.

BE PLANT WISE!!

Download these posters and promote in your area.

Current Legislative Position (Listed on 02 August 2017)

This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.

For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk

Species Related Files:

NIEA ID Guide Heracleum mantegazzianum Giant Hogweed

Giant hogweed

Heracleum mantegazzianum

Overview

Species Related Files:

Invasive Species Northern Ireland