How to Control and Kill Giant Hogweed

Giant Hogweed

How to Control and Kill Giant Hogweed

Hazardous plants like poison ivy and poison oak are synonymous with skin irritation and allergic reactions, but there’s one weed out there that makes them look mild. Giant Hogweed presents a whole new level of skin reaction, which can lead to third degree burns. The sap of the plant triggers a chemical reaction on your skin called photodermatitis. This means that your skin becomes extremely sensitive to the sun’s UV rays, making you highly vulnerable to severe burns after only a few minutes outdoors. The resulting lesions and blisters usually start to go away after a few days, but it’s possible for that patch of skin to suffer photosensitivity for years afterwards, and to have problems with correct production of melanin, the substance which pigments our skin. Contact with your eyes can cause temporary or even permanent blindness, making this a seriously dangerous weed.

Giant Hogweed, native to the Caucasus, was brought to the Britain and U.S. in the 19th century and has flourished at the expense of native plants. For the benefit of your local ecosystem and the safety of your community, it’s important to manage the growth of the weed. There are a number of ways to kill Giant Hogweed, but it’s by no means an easy or quick process. Proper management requires several techniques used over the periods of the plant’s growth cycle, as well as regular checks for regrowth.

Always try to manage your hogweed plants before they have flowered, and catch them as small as possible. Giant hogweed has its name for a reason – it can grow up to 10 feet tall, not exactly a manageable size for one individual. Let’s have a look at the recommended procedures:


If your Giant Hogweed is still small and doesn’t yet have seeds, you can mow over it. This won’t kill the plant immediately, but repeated mowing will starve and weaken the roots. This can cause the plant to wither and either gradually die or allow you more easily dig up the roots at a later date. If you are going to mow the plant, it’s essential to do so on a regular basis, because a single mow can actually encourage new root growth. Under no circumstances mow a plant with seeds. This will simply disperse the seeds and allow the weed to spread further. Mowing can also spray sap onto you, your mower or the ground, so use extreme caution to avoid contact.


Getting directly to the ‘root’ of the problem works literally in this case. Digging out the roots is the most effective natural method for killing Giant Hogweed. Cut plants down and then dig out the roots. Cut the taproot (central, dominant root) around 6 inches below ground level and remove as much as you can. This will discourage growth, but won’t kill the plant until you remove almost the entire root. If growth continues, repeat the process every 1-2 weeks until you get enough out for the plant to die. If you don’t mind using a herbicide, you can apply some to the part of the cut root that remains in the ground , to stop it from growing next season.

Seed Disposal

If you have trimmed or dug out a plant which has seeded, place the flowers and seeds in a clear plastic bag and leave them in the sun for two weeks. UV exposure will render the seeds insert and make them safe to throw away without any worry about them geminating later.


Farmers or homesteaders may be able to let their livestock take care of the problem for them. Cows and pigs are immune to the damaging effect of Giant Hogweed sap, so they can eat and trample the weed. This won’t kill it, but can manage growth reasonably well. Be careful around animals that have come into contact with the plant, as sap can rub onto your skin from your animals’ hides.


If your weeds have grown too big or haven’t responded to non-chemical treatment, you can use herbicide to kill them. Giant Hogweed is susceptible to chemicals like glyphosate and triclopyr. Apply yourself, or call a qualified professional to do it for you. These herbicides will kill the plant, but won’t prevent seed germination, so you may need more than one application. In fact, applications may have to be done for several years in a row, depending on the severity of the infestation. If possible, cut of the top off the plant, remove the seeds and dispose of them as directed above.

Once your plant seems to be gone, monitor the area over the seasons for new growth. If no new shoots spear, plant the area with a native replacement plant to ‘crowd out’ possible further infestations.

Always wear protective gear and keep your skin covered when handling Giant Hogweed – safety first at all times!