Posted: 19/07/2013 at 17:37
Isn't giant hogweed a bi- or tri-annual? If you manage to get every plant every year so none of them ever produce a seed, it should be scarce four years from now. I think the seeds have been known to wait up to seven years and then sprout again, though, so you'd have to stay vigilant, and if you have a riverbank in that meadow it'll get seeds washed up from further upriver.
Some sprayers have an optional sponge attachment that you can use to wipe weedkiller on to leaves without spraying at all, but you'll get sap on the sponge, so don't touch it afterwards!
Actual eradication plan if you are on a river:
Get an army.
Start scouts at the tops of tributaries, each equipped with a map and a pen. Each scout follows one side of a watercourse downhill, marking on the map every hogweed found.
Copy all hogweed finds onto your master map at HQ, and mark them with the date.
Send out sprayer crews to the hogweeds furthest up each watercourse. Each crew needs a spotter to make sure they don't do something stupid, a sprayer to deliver the toxin and a chopper with a really long spear to lop off flower heads. Each crew marks as far down the river as they got before they ran out of ammo or the wind came up.
Repeat spraying on suitable days until your teams get downstream of you.
Repeat the whole process next year, and the year after that, and the year after that and so on for eight years. Starting in year nine, you can start your scout teams a little further downstream, because any watercourse where no plants have been found in 8 years can be declared clear.
Once the scouts are starting downstream of you, you can declare local victory, and then find out that someone's transported seeds or contaminated soil to a site upstream of you and the b*****d things are BACK.
So, ah, which river valley are we doing first?