I’m fortunate to have several rhubarb plants in my backyard that produce stalks from mid April to September. I’ve found that most well-stocked grocery stores and farmer’s markets sell fresh rhubarb in early spring. One thing to keep in mind is that the flavor of rhubarb changes over the course of the season. Stalks picked later in the season are more tart than those earlier in the season, and the amount of sugar in recipes will need to be adjusted accordingly.