Vegetables that are to be frozen must first be blanched (scalded) if the greatest possible amounts of color, flavor, texture, and nutritive value are to be retained. Of the vegetables that have been tested, rhubarb is the only one that is satisfactory when it is not blanched before being frozen. Precooking beets and winter squash makes them easier to handle than if they are blanched. Tomatoes are simmered before the juice is extracted.

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Vegetables that are to be frozen must first be blanched (scalded) if the greatest possible amounts of color, flavor, texture, and nutritive value are to be retained. Of the vegetables that have been tested, rhubarb is the only one that is satisfactory when it is not blanched before being frozen. Precooking beets and winter squash makes them easier to handle than if they are blanched. Tomatoes are simmered before the juice is extracted.

http://www.extension.uiuc.edu/...

Don't cook or blanch your rhubarb before freezing. Cut in one inch pieces, spread evenly on a baking sheet - freeze! A few hours later remove frozen pieces from baking sheet and put in freezer bags. This method prevents it from clumping together. This works for strawberries too! If you're making a rhubarb pie, place frozen pieces in a pie shell, sweeten to taste, and bake as usual. The rhubarb cooks nicely, but doesn't turn mushy and wet the crust!...

Don't cook or blanch your rhubarb before freezing. Cut in one inch pieces, spread evenly on a baking sheet - freeze! A few hours later remove frozen pieces from baking sheet and put in freezer bags. This method prevents it from clumping together. This works for strawberries too! If you're making a rhubarb pie, place frozen pieces in a pie shell, sweeten to taste, and bake as usual. The rhubarb cooks nicely, but doesn't turn mushy and wet the crust!