Off-Flavor of the Week: Grassy

A beer that smells or tastes like the lawn you just mowed is likely to disappoint.

Dave Carpenter Nov 7, 2014 - 4 min read

Off-Flavor of the Week: Grassy Primary Image

Everyone loves a good lawnmower beer from time to time. So named for the refreshing, thirst-quenching properties that make them so welcoming after mowing the lawn, lawnmower beers are usually light in color and alcohol and best served cold. Cream ale, Pilsner, Kölsch, Helles, and, yes, even American lager can be just the thing on a hot summer’s day.

However, a beer that smells or tastes like the lawn you just mowed is likely to disappoint. The Beer Judge Certification Program (BJCP) describes grassy beer as having the aroma or flavor of fresh-cut grass or green leaves.

Some amount of grassiness is to be expected from certain hop varieties. Fuggle, Mosaic, Tradition, and Boadicea hops, among others, can lend grassy notes, especially when employed as late-kettle or dry hops. I once drank a commercial beer that was dry hopped with Fuggle and served from a firkin, and all I could think of was wet hay.

If the hops variety isn’t the culprit, then the issue may come down to ingredient storage. Both malt and hops can take on musty, moldy, and grassy notes if they’re improperly stored or simply stored too long. A certain musty character is even appropriate in Bières de Garde, though it is said that this is more related to storage of the final beer than to its constituent ingredients.

Grassy notes can also crop up when lots of hops material makes it into your beer. All of that hops matter that sits at the bottom of your kettle after the boil should be separated from the wort before or during transfer into the fermentor. Using a high alpha acid hops for bittering lets you get away with less hops material to achieve the same bitterness you would otherwise obtain from large amounts of a lower alpha acid variety.

Finally, dry hops can lend a vegetal, grassy flavor if they’re left in contact with beer for too long. Generally, a week of dry hopping is sufficient, although up to fourteen days is usually fine, too. Avoid dry hopping for more than two weeks, though, to keep the grass low.

In summary, you generally don’t want your lawnmower beer to smell or taste like an actual lawn. If you’re struggling with grassy aromas and flavors, give the following suggestions a try:

  • Use the freshest malts and hops you can find, and make sure they’ve been properly stored.
    Switch hops varieties.
  • Use small quantities of high alpha acid hops for bittering rather than large amounts of low alpha hops.
  • Don’t allow boiled hops in the fermentor. Separate them from your chilled wort as it leaves the boil kettle.
  • Reduce the amount of contact time between dry hops and your beer.