Aspirin, a well-known pain reliever for humans, has interesting effects on plants. Gardeners have discovered that salicylic acid in aspirin helps plants boost their immune system and promotes growth. Plants naturally produce salicylic acid, in small doses when damaged or stressed, as a defense hormone. This defense hormone helps plants by stimulating growth and boosting its immune system which increases the plant’s resistance to stress from drought, heat or cold, as well as disease. Aspirin, specifically its salicylic acid content, is a supplement to this process.
Aspirin contains salicylic acid in the form of a compound known as acetylsalicylic acid. When exposed to water, the compound acetylsalicylic acid is broken down and salicylic acid is released. This water solution can then be used as a foliar spray. The salicylic acid solution sprayed on plants activates a defense response that empowers them to fend off diseases and stress more effectively.
Make a salicylic foliar spray by dissolving three crushed non-coated aspirin into four gallons of distilled water or boiled water cooled to room temperature (due to harmful chemicals in tap water). Be careful not to increase the concentration as it can harm plants. Make sure the aspirin is well crushed as it needs to be completely dissolved to be effective.
Pour the water solution into a spray bottle and let it sit for several minutes before shaking well. The best time to spray this solution is early in the morning to prevent harming beneficial insects and pollinators when they are active. Avoid using the spray more than once a month. Too frequent a use can harm plants.
Although salicylic acid naturally occurs in plants, not all plants tolerate higher levels. Keep an eye on the plant to see how it tolerates the spray. Nightshade plants, such as tomatoes, potatoes, eggplant and peppers, do well with this foliar spray.
There are mixed reviews (some agree and some disagree) on suggestions for using this solution in different ways. Some suggestions say to soak cuttings in the aspirin solution for half an hour before planting to stimulate root growth. Other suggestions say to apply the solution to the surface of the soil above the roots after planting. A more common suggestion is to use the solution for cut flowers to extend their life.
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