Likes well manured soil and is often found on the grass verges next to bridal paths. Though not growing directly on manure. The psychedelic affects are associated with the mushrooms high concentrations of Psilocybin with concentrations of 0.8-1mg per gram of dry weight.
Mushroom poisoning can be an extremely horrible way to die.
Often the individual poisoned believes that after a brief period of sickness they are better, to find 2 days later an emergency trip to the hospital is required. Eating fresh Psilocybe semilanceata in the UK is legal, if you believe you may have consumed a poisonous mushroom go to your doctor or hospital, it is better to be safe than sorry. If that is really what you are going to be up to in Autumn - take someone who knows what to look for. The Psilocybes are a large group of mushrooms, many of which are little brown mushrooms, and are harmless. Within this grouping, however, exist a few species that are known to have varying affects upon ingestion, including hallucination.