There's an article on this topic in the current Gardener's World mag.
It says (abbreviated)

"the Horticultural Trades Association has worked in close ssociation
with the National Poisons Unit at Guy's and St Thomas Hospital Trust and
tha Royal Botanic gardens kew, to produce a list of recommended retail
practice...it includes a list of 120 potentially harmful plants...based
on medical case histories involving plants that have been identified as
being a significant hazard. The plants are divided into 3 categories of
hazard.

the full list can be obtained from the HTA tel 0118 930 8940, or at
www.gardenersworld.com."


I enjoyed "Capsicum annuum,chilli pepper..eating the fruits causes
sweating and a burning sensation".

Notta lotta people know that...

Janet