Rhubarb is one of my favorite edible plants because of its delicious flavor in all sorts of foods. For those of you who do not know, you eat only the stalk of rhubarb and throw the leaves away. I'd always wondered if there was something I could be doing with those leaves instead of just throwing them away so I was very happy when I came across the idea to make a pesticide with them. Anyone who has gardened before knows how irritating it can be when insects or other pests ruin or destroy your plants. As I didn't see any other Instructables on how to make a pesticide from rhubarb I figured I'd share my method. This spray is organic (as long as your rhubarb is) and it actually kills insects instead of repelling them.
IMPORTANT: Rhubarb leaves contain high amounts of oxalic acid which is toxic if consumed. This is why it works as a pesticide and it is also why you should keep the spray away from small children and pets. You shouldn't use it on edible plants when you are going to eat the entire thing (lettuce, spinach, etc.). If you are going to use it on edible plants I'd say try to spray them before they start producing whatever part you are going to eat and wash it afterward.
Step 1: Preparing the Leaves
After you've used the stalk of the rhubarb for whatever you want, save the leaves instead of throwing them away. Cut them all into pieces about 1-inch square. After you've cut them, clean the cutting board or whatever surface you cut them on so there are no traces of the harmful acids.
Step 2: Boiling the Leaves
Measure the leaves you just cut. For every cup of leaves, boil one cup of water in a pot. Once the water is boiling, add the leaves all at once. As soon as they are in the water, turn the heat to low. Leave the pot on the stove for 25 minutes allowing the leaves to simmer.
Step 3: Finishing Up
After 25 minutes has passed, strain the leaves out of the water. I found a good way to do this was to wrap an old cloth (cheesecloth would work fine) around the top of a plastic cup. I then took a second plastic cup and put the first into it. The second cup helps to hold the cloth in place as you pour the spray into the cup. After all the leaves are collected on top of the cloth, bundle it up and squeeze it out to get all the pesticide into the cup.
The liquid you now have is concentrated and can be stored once it cools
IMPORTANT: Label the container you use with something that will tell others it is toxic
Step 4: Using It
Mix the concentrated solution with water in a ratio of 1:2 respectively. Put this in a spray bottle and it is ready to use.
As I stated earlier be sure to keep this away from small children. If you are going to use this on edible plants consider what parts are going to be eaten. If you know your pets chew on your plants make sure they cannot reach them after you spray them.
Thank you for reading my Instructable! If you want to see more of my projects subscribe to my youtube channel here.