At Holistic Health Group’s farm in Middleborough, dozens of vacuum-sealed bags full of marijuana flower — worth hundreds of thousands of dollars at retail — have been sitting in a secure vault for months, stuck in limbo.

The problem? The marijuana, which was grown outdoors last season, flunked the strict laboratory tests for microbes that all legal cannabis in Massachusetts must pass before sale.

The standards are intended to protect consumers from moldy or bacteria-contaminated flower. But farmers across Massachusetts have complained that the state’s unusually tight rules are based on flimsy science, discourage outdoor growing and other sustainable practices, add to the high cost of pot, and defy the simple fact that cannabis is a plant, one adapted to grow in soil rich with microorganisms.