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Control of Giant Hogweed

River Severn Custodians’ approach to controlling Giant Hogweed

General information

It is best to tackle the plants in spring when they are about knee height.  This reduces the amount of danger from sap spray.  We started out with large plants in our first year but since then we keep an eye on hot spots and tackle them as soon as they are identifiable. 


Although you will never completely eradicate the infestation if they are being reseeded from upstream, rest assured that the problem will become very manageable after a year or two and will require much less work.


By following the instructions below you should be completely safe.  None of our members has ever had an incident of sap burning in the more than 7 years we have been tackling the hogweed.


Giant hogweed causes severe burns when sap on the skin is exposed to sunlight.  The object is to never get sap on bare skin.  Do not touch the plant with bare skin- toxicity can result from any action that involves bruising, cutting or touching the foliage, stem, flower or fruit. Do not touch your exposed skin with sap covered gloves!


If controlling plants in groups of several people, keep a good distance from one another as the sap can splash three to four feet while doing control and also there is the risk of accidents with the long, sharp tools.


Wash equipment with water immediately after use. We dip our tools in the river before leaving and wash them more thoroughly when we return.


Before starting load on 30 or 50 factor sun cream on any exposed skin on the face and neck.  This prevents ultraviolet light from reaching the skin so any sap can’t be activated to burn.


We carry water and a first aid kit with us in our work area in case of exposure to sap or other mishaps.


Wear wellies, walking or work boots, socks, long trousers, long sleeved shirts buttoned to the neck, long waterproof gauntlets or gloves to cover the shirt sleeves, goggles or safety glasses and a hat (Figure 1).  Synthetic water-resistant materials are best, since cotton and linen fibres can soak up the plant sap and be penetrated by plant hairs (e.g. dishwashing gloves, rain suit or tyvek suit, and rubber boots).


Change out of work clothes and wash yourself with soap and water after doing control. Limit exposure to sunlight after control. Launder clothing that may have contacted plants.  At small sites, some people have chosen to work around giant hogweed plants after sunset to limit their exposure to sunlight.


Figure 1.  River Severn Custodians after a session.  Note the RSC high viz vests.  Some people are still wearing the long gloves we recommend.



DO NOT use a power strimmer – sap may splatter on you as stems are cut.


After experimenting with several options, the tools we have found most effective are long handled slashers for cutting any long stems and a trenching spade for digging out the roots (Figure 2).  We bought both of these, brand name Spear & Jackson, from Charlies in Newtown.


When the plants are small only the spade is needed.  Some people find it heavy and prefer something a bit smaller.  The tools must be strong, however, or they will bend and break under use.


First cut off all stems close to the base and use the spade or slasher to flick them gently away from your working area.  This exposes the base of the plant and makes them less viable if you don’t get all the root.  Using the spade, then dig down into or just beside the base and cut away any root you can get access to.


Leave all the plants in the area but away from any footpaths or play areas.  After a few hours the plants lose all toxicity and simply mulch down.  There is no need to remove them from the site, cover them or treat them in any way.


When the plants are small they might be confused with native hogweed.  After a few sessions you will get to know the difference.  In the meantime, our policy is, “if in doubt, cut it out”.  Even with this policy the native hogweeds are recolonizing the areas we work and taking over from the Giant Hogweed.


Figure 2.  The tools we have found most effective for tackling Giant Hogweed.