Well, we had an expensive trip to the vet yesterday. I am aware of which plants in the garden are poisonous and have always been careful, and Dylan so far had never been one for eating the vegetation. I was moving some snowdrops, and put them on a table in the back garden while I went round the front. Then OH came round to say he saw the boy eating one. Cue phone call to the vet and a trip for an injection to make him sick. Home with some liquid charcoal to add to his food (ugh, thick black viscous liquid, 40ml is a lot of stuff to add to a meal - fortunately he still ate his food). No ill effects thank goodness, except the bank account is £80 lighter.
When my dogs have swallowed something bad in the past I have used washing soda to make them vomit, but the vet didn't seem impressed with this, and as it was poison rather than some inanimate object I thought it best to be on the safe side.
Lesson learned