It is my understanding that beekeepers either
A. 'Lease' their bees out to farmers and drop them off to forage, such as is the case during apple season; The beekeepers get the honey and some cash, and the farmers get their crops pollinated. In this case there is a 'target' crop(apples) and the bees take the nectar from them because they are so abundant and there are so many of them. I am sure some wildflower nectar makes its way into the honey but its probably minuscule.
B. Let the bees forage from what naturally grows around them. This is called wildflower honey iirc.
C. Keep their bees in a field of a certain type of flower(ie clover)
One could hypothetically plant a ton of monkshood(highly poisonous) and other plants which grow naturally in the area where the hallucinogenic honey is harvested around the bees. I don't think the exact chemistry of the honey could be replicated though. It could be potentially dangerous doing so. I'd advise against it.
On another note, I've always wondered about what the effect on the honey would be if the bees were kept in a field of poppies.