Unlike the leafy greens of many root vegetables like radishes or carrots, the leaves of rhubarb aren't edible. They have high levels of oxalic acid that can damage your kidneys and even lead to death if ingested in very high levels. That doesn't mean rhubarb leaves have to become a food waste statistic. Here are some non-edible uses for rhubarb leaves.
1. Shine pots and pans. Oxalic acid is an active ingredient in products like Bar Keepers Friend, a non-abrasive powder that cleans and shines stainless steel and other surfaces. When you boil rhubarb leaves in stainless steel pots and pans, it can help give the pots a beautiful shine. Wash them well after to remove any residual oxalic acid.
2. Repel pests from leaves of non-edible plants. The Rhubarb Compendium website has instructions for boiling leaves in water and combining the strained water with soapy water to create an organic pesticide.
3. Get crafty and use them to make stepping stones. Rhubarb leaves can grow to be very big and when used as the template for a cement casting, they make beautiful leaf-shaped stepping stones. Savor the Rhubarb has a tutorial on how to turn these leaves into garden decor.
4. Use them to create a green dye. Dye yarn and other materials using water that's been boiled with rhubarb leaves. Colour It Green explains the easy process. Do NOT use rhubarb leaves to create food dyes.
5. Compost them. The oxalic acid will break down as the leaves decompose, so it won't create a poisonous compost, according to Gardening Know How.