How do we get rid of acanthus

We have several clumps of Acanthus in our garden and would like to get rid of them. No success in trying to dig them up as there always seems to be a tiny bit left which then grows into another plant. The roots are really deep and some seem to be amongst unmovable stones. As suggested by a local gardener we tried painting onto the leaves neat Roundup mixed with a little Fairyliquid (?!) but this only seemed to kill those particular leaves and up sprang new growth. We do not know exactly which variety of Acanthus we have - only that we want it gone. We live in Cornwall. Would appreciate any suggestions.

Thanks
Suzanne

Re: How do we get rid of acanthus

Reply from Kathy C

Hi, Suzanne,
You are not alone with Acanthus taking over - I have been tackling some for about a year. If you search forums here on Shoot, you will find many more with trouble eradicating it. It is as difficult as ivy to get rid of. It will take vigilant digging/pulling out of any sprouts. You can try digging down about 30cm or so in the offending area, removing all root you see and then replacing that soil with untainted topsoil. If it were possible, the best method is to cover the ground where it is with thick black plastic sheeting and leave it there for at least 6 months. This will smother it but not a really feasible method if the offending bits are surrounded by desirable plants.
Best of luck!
Kathy C

Re: How do we get rid of acanthus

Reply from Joan Stewart

I am doing battle with some Acanthus at the moment and have had some success in the past with painting the remaining cut shoots with tree killer. You have to be very vigilant, attacking it as it comes up. I did manage to erradicate it from one part of the garden, but it took some time. Digging it up only seems to spread it further as every cut root shoots up another plant.