Should I put that I am taking marijuana as medicine for my physical?

I believe if I were you, I'd tell them about the "prescription card" for "medical marijuana". They likely won't find any evidence of recent use, but at least you've been honest and can explain the condition under which you occasionally must use marijuana. If they found out later on, they could likely dismiss you for making a false report and signing it knowing full well that you have a prescription to buy and use medical marijuana. More and more doctors are allowing the use of medical marijuana now than ever before. I don't believe that medical marijuana usage has the stigma attached to it now that it did several years ago, as more doctors learn that it's the only pain relief that some people can get when stronger prescription drugs have negative effects on their body. I believe I'd take the chance that they'll understand the reasoning behind this. At least they would know they're possibly hiring an honest person, and that can mean a lot these days. If you do a great job working for them and show up every day, they'll think nothing of it. Good luck with getting the job!