Hops are a new plant included in the 1.2.2 update.
These require a O-Straight Support in order to plant.
To harvest Hops, you must destroy the Hops plant when it is fully grown. This drops 1-3 Hops along with 1 or possibly more Hops Sprouts, as well as the used O-Straight Support.
Their only other use so far is to craft a O-Beer Mug.