I've actually taught wild food foraging, as I studied Biology prior to entering catering (I know, I know) and it's a cool way to combine the two.
I cannot iterate strongly enough the mantra, if in doubt, chuck it out (ANY doubt.), even if you're slightly uncertain, reference, cross reference, cross reference again (and not just online). Also remember, even if you use a specialist online foraging forum for ID'ing, remember all you'll get with a photo is a 'best guess', and may just confirm it is what you think it is. If there's an inkling of doubt...no.
Local colleges and universities are usually pretty helpful if you do want an ID, but if you want to eat 'Food for Free' why not have a day course in your local area there are loads about.
I've been seriously foraging food for over 25 years and still apply the above to myself!!!