Rhubarb leaves can be used to make an effective organic insecticide for any of the leaf eating insects (cabbage caterpillars, aphids, peach and cherry slug etc).
Recipe 1
Basically you boil up a few pounds of rhubarb leaves in a few pints of water for about 15 or 20 minutes,
allow to cool,
then strain the liquid into a suitable container.
Dissolve some soap flakes in this liquid and use it to spray against aphids.
So, next time you pick some rhubarb stems to eat, you can put the leaves to good use rather than just composting them (which isn’t in itself such a bad use, I guess). http://ow.ly/i/GF8m