Mike wrote:
Sign saying the plant is highly toxic and anybody touching it with bare
hands will suffer an agonising death ?

The neds will only start smoking the leaves for a 'high' and then get
their lawyers to sue you when anything/nothing happens.

If you put a notice up saying "Healthy Fresh Salad Leaves - Please Pick
Your Own" the plants will be left well alone, as (a) neds are allergic
to anything fresher than a kebab (b) as you're inviting them to touch
the plant the excitement of doing something prohibited is lost.

Owain