Choosing quality rhubarb for your crisp is important. You want nice, firm rhubarb stalks. You should not have any mushy stalks or speckled spots on your rhubarb. Be sure not to use the leaves as these are poisonous to pets and humans. Discard the leaves accordingly. Garden fresh rhubarb is best used in the spring or early summer. Typically April through June is a good rule of thumb. To preserve your harvested rhubarb, chop the stalks and store in the freezer for up to 1 year so you can enjoy it year round!