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Aspirin, when used in gardening is typically not recommended for direct applications to plants for disease or pest control. There really have not been any evidence or studies to show it is beneficial.

There is a " natural" ingredient in some plants such as spiraea that is salicylic acid, but aspirin is acetylsalicylic acid a slightly different chemical compound. Because there is no evidence that a spray of aspirin prevented or treated any plant diseases it is not something that is recommended.

My other concern is if your food was eaten by someone that is allergic to aspirin it could  be very dangerous.

If you're looking for ways to improve soil health or protect plants, it's best to stick with proven methods and products that are safe and effective. 

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