Talk about multitasking: Rhubarb (Rheum x cultorum, Rheum rhaponticum, Rheum rhabarbarum) grows as a vegetable, lends a tropical touch to an ornamental garden and supplies the delightful tang in strawberry-rhubarb pie. Gardeners in search of organic insect control can add one more credential to rhubarb's resume. The oxalic acid that makes its ruffled, rounded red-stemmed leaves toxic to people and pets also kills plant-infesting bugs like aphids when processed into pesticide spray.
Things You'll Need
- Clean, sharp knife (optional)
- Household bleach (optional)
- Chopping board
- 1-quart anodized aluminum, stainless steel or ceramic saucepan
- Fine-meshed strainer
- 2-quart bowl
- Large spoon
- 1-teaspoon measuring spoon
- Measuring cup
- Liquid dish soap
- Spray bottle with blank label
- Container with lid (optional)
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Place harvested rhubarb leaves on a cutting board and chop them coarsely with a sharp knife. Clean the board and knife thoroughly when finished so oxalic acid from the leaves doesn't contaminate other food.
Pour 4 cups of water into a ceramic, anodized aluminum or stainless steel saucepan. (Oxalic acid from the cooking damages other metals.) Add the chopped leaves, set the pan on the stove top and bring the water to a boil.
Let the uncovered pan continue boiling for 30 minutes, adding water as necessary to replace what evaporates. Take it off the stove and set it to cool where kids or pets won't reach it.
Strain the cooled liquid into a 2-quart bowl. Using a fine-mesh strainer, press down on the leaves with a large spoon to release all their insecticidal compounds.
Dissolve 2 teaspoons of liquid dish soap in 1 cup of cold water. Add the solution to the strained liquid, blend thoroughly and funnel the mixture into a plastic spray bottle. Label the bottle with its contents and mark it as poison. If any of the mixture is left, store it in a sealed, labeled plastic container away from kids or pets.