Giant Hogweed treatment

[waterbuoy]

OK, I know this is an arb forum and my question is not related to trees.  However, I suspect some members may have more experience of this than most (and have not been able to find much using the search function).

 

We have a rather splendid (?) trio of Giant Higweed plants in our garden.  They have yet to flower, but are some 4' high and each has a spread of c. 6'.  I am keen to treat them before they flower.

 

In the past we have used Roundup Pro Biactive which seemed to work OK, although since tlast using it we now have a small dog.  I understand that this has now been replaced by a new version of Roundup (I think Roundup ProActive) but the original can still be obtained from suppliers.

 

My question is:  what would you recommend for treating Giant Hogweed?

 

Thanks in anticipation ........

[Peasgood]

I would paint the leaves with 50:50 Roundup and water.

Or replace water with diesel to make it stick, or mix the Roundup with cooking oil before adding to water.

All will work and the weed is more harmful to your dog than Roundup ever would be.

[Baldbloke]

Used to do about 14 miles of riverbank spot spraying Hogweed. You don’t need a mix at 50:50.
250ml for 15 litres of water is more than strong enough. So 25 cc/ml for 1.5 litres would probably be adequate for 4 plants. If the weather’s dry you don’t need a adjuvant/surfactants/stickers. It’ll be about a week before you’ll start to see leaf discolouration.

Spraying on riverbanks in the north of Scotland was best done late in April as soon as the immature plant was recognisable, but before it needed gallons of spray near watercourses.

[doobin]

6 hours ago, Peasgood said:

I would paint the leaves with 50:50 Roundup and water.

Or replace water with diesel to make it stick, or mix the Roundup with cooking oil before adding to water.

All will work and the weed is more harmful to your dog than Roundup ever would be.

Jesus mate did the gypos hijack your account?? why not add some agent orange while you're at it?

 

If you've just three single plants in a garden setting, I'd pop on a coverall and gloves (facemask if you wish) and carefully snip each stem and chuck it onto a lit bonfire. Then the roots should be fairly easy to dig out and add to the fire. Any regrowth can then be treated with spray whilst it's young and soft. Why go throwing large quantities of pesticides onto tough, mature plants when you can deal with them in ten minutes fairly permanently?

[Peasgood]

1 hour ago, doobin said:

Jesus mate did the gypos hijack your account?? why not add some agent orange while you're at it?

We used to buy Codacide in 200 litre barrels to mix with glyphosate, it almost doubles the effectiveness of the glyphosate, Codacide is nothing more than vegetable oil and was sold specifically for that purpose. All legit, all as per label. It was used more when glyphosate was expensive and vegetable oil was cheap, these days it is more econimic to just up the glyphosate rate.

Diesel is also a recognised sticking agent, I have even seen that as a label recommendation too (admittedly not with glyphosate). I very much don't advocate its use on any large scale but enough to paint three Giant Hogweed plants is hardly going to give Greta sleepless nights. 

 

I will also bet £1 that they aren't Giant Hogweed either. Probably a hogweed of some description and any of them will cause photosensitivity but Heracleum mantegazzianum are fairly uncommon.  (no disrespect to the OP intended).

[Stere]

Quote

I will also bet £1 that they aren't Giant Hogweed either. Probably a hogweed of some description and any of them will cause photosensitivity but Heracleum mantegazzianum are fairly uncommon.  (no disrespect to the OP intended).

 

Yeah often being told "we have have giant hogweed" at its always just regular Hogweed.

 

Regular hogweed  still cases me blisters  ?

 

 

For OP If just has 3 plants why not just dig up or trim down mow area?

 

 

[waterbuoy]

Thanks for all your suggestions.

 

With regard to whether or not it is Giant Hogweed - I have had three FC people all independently confirm that it is (as my sister in law declared on her one and only visit to see us we are 'long on trees and short on shops'!) together with the couple who run the local nursery.  As we spend a significant part of our year working at Environment Agency sites on river banks I suspect that I brought the seeds back in the copious amounts of mud that usually coat the underside of our vehicle after such trips.  All three plants are at the edge of our gravel driveway.

 

The reason for asking the question on the forum is that all the people gave different suggestions as to how we should deal with it and, given their respective backgrounds, I was aware that they were perhaps being more conservative than some of the agent orange type approaches suggested above!

 

On the basis of what has been suggested I will cut the plants back this evening when we have our weekly 'lockdown bonfire' and burn them.  I'll have a go at digging out the rootballs and burn them too.  If/when shoots start to re-emerge then I'll treat with roundup and see how we go.

[Mesterh]

Looks like we have some common hogweed about the place, I say that as it looks like giant hogweed but is no where as big. I assume it is still fairly nasty. Time to dig out the glysophate pro me thinks.

 

[headgroundsman]

13 hours ago, Peasgood said:

 just up the glyphosate rate.

Upping the glyphosate isn't always helpful and often wasteful. It can also be counter productive! It needs to be translocated onto the root system to work properly. If too strong it can kill off the top growth before killing the entire root system. Rarely is greater than 40:1 needed

 

[openspaceman]

17 minutes ago, headgroundsman said:

If too strong it can kill off the top growth before killing the entire root system

This is basically what a late friend , a biochemist and forest manager, told me. Too strong and it traumatises the plant and it doesn’t translocate.

 

A bit like whisky, it hits the spot quicker with water.