I was 15, and it was morning glory seed (hence the name). At 17, got into trying mushrooms and LSD. Tried the 'experimental psychedelics' around 24.
No one asked, but I am going to say it anyway....I certainly don't regret using psychedelics at such a young age, and I can't see that any harm came from it. However, I never really 'got much', nor was I mature enough to really understand those experiences until I was much older. I'd say around 21, 22 is when my psychedelic trips really started having a major impact as far as my outlook into spirituality and the world around.