How much suspension of disbelief did Shakespeare require of his audience when he chose the plot strategem of the herb that induced a death-like trance in Juliet?

Some herbs do, of course, have powerful medicinal effects; the mandrake, pictured here, is a powerful narcotic, and its imagined similarity to the human form meant that many magical properties were attributed to it.

Both conventional medicine and the less official (but possibly more effective) medicine practiced by the housewife employed herbal remedies.