A vertical tasting is trying a selection of the same beer from different years. It is a great way to see how a beer changes over time. It is especially exciting when done with wild ales because the flavors imparted by souring bacteria can greatly change over periods of time.
This vertical was between a 2009 and 2010 bottle of Weyerbacher Riserva. This American Wild Ale with raspberry puree has a wonderful tangy tartness and mild levels of funk.
It is amazing the difference a year can make. The 2010 was much sharper with the flavors hitting you in distinct steps while the 2009 was much more rounded and allowed the tastes to gently flow together. The 2009 finished drier and invites the drinker to take another sip while the 2010 makes you pucker a little and prepare yourself for another taste.
It will be very interesting to see how this beer changes over the next few years.