Rhubarb is an intriguing plant, with edible red stalks and a poison in every large, green leaf. The stems are traditionally used as an ingredient in desserts, but have an even wider range of cooking uses. The leaves, however, kill. The poison in the leaves is oxalic acid, which will stop the human heart if ingested.
However, the leaves can also be used to make a natural pesticide that breaks down quickly and disposes of many unwelcome bugs without inhibiting the presence of beneficial bees. Below are two ways to use rhubarb leaves to protect your garden from insects.
Step 1 - Boil
Place the rhubarb leaves in the pot and cover them with water. Boil the water and leaves for 20 to 30 minutes. Then remove the pot from the heat and let the contents cool.
Step 2 - Strain
Strain the resulting liquid into a spray bottle. Dispose of the boiled leaves.
Step 3 - Add Soap
Add the dish detergent and mix the liquid well. When choosing a soap to add to your rhubarb pesticide spray, avoid harsh detergents and soaps with a long list of chemicals. The chemicals will damage your plants and contaminate your garden soil.
There are garden soaps and biodegradable soaps available that will protect your plants from insects without causing further harm. Also, using a spray of just soap and water can be a useful pesticide.
Step 4 - Use
Spray the resulting liquid on your plants to kill aphids and other disruptive insects. Do not use rhubarb spray on food-bearing plants. The poison will break down quickly, but there is still a risk that the sprayed food will have oxalic acid on them.
The rhubarb spray will rot, so use it quickly or freeze the mixture to store it. If you store it, be sure to accurately label it as poison.
Rhubarb Leaf Protectors for Seedlings
Save rhubarb leaves when harvesting your rhubarb. Slit the rhubarb leaf along the fleshy central vein to create an opening. Place the opening in the leaf around the young seedling you wish to protect. The leaf will provide shade to the soil, retain moisture, and provide nutrients while decomposing.
These functions are in addition to the work the oxalic acid will do repelling insects.
The leaf should decompose in three to four weeks. By that time, your seedling will be strong enough to survive on its own. If further insect-repelling is needed, use the rhubarb spray described above. However, while the rhubarb leaf protector can be used on food-bearing plants, the spray cannot.