I am getting a what I describe as a veggitable flavor and smell about every eighth batch. What could cause these off flavors?
Most likely DMS which can come from using Pils or very pale malt and either 1) not chilling fast enough 2) boiling with the lid on or 3) not boiling long enough (or a combination of any of the above.) Another culprit of DMS is infection.
In darker colored beers I have noticed vegetal flavors/aromas coming from chlorine in the water.
I have found some hoppy beers in Belgium tasted a bit like vegetables, but in a good way. Westvleteren Blonde is the clearest example I can think of. I think excess amounts of noble hops can produce it - I think of it as a raw green bean flavor…