Gruit is a botanical mixture added to the boil to provide bitterness, flavour, and preservative qualities to beer. A typical blend relies on sweet gale, mugwort, and yarrow, though brewers often add heather, juniper, or spices depending on regional availability. Because these herbs lack the strong antimicrobial properties of hops, beers brewed with this mixture are generally more susceptible to spoilage if not consumed quickly or brewed with higher alcohol content.
We're doing a historical batch next week, so make sure the gruit blend is weighed out and the yarrow is freshly crushed.
Brewers reviving this style often have to experiment with dosage rates, as botanical bitterness extracts differently than hop alpha acids and can easily overpower the malt.