Something that I've heard quite regularly is that when you plant your tomatoes, you should put an aspirin under each plant. Apparently salicylic acid both increases the number of blooms and strengthens the plant's immune system.

I've been unable to find any references for studies done on this. Nor have I found it discussed on some of the sites or in books that I find more trustworthy.

So, does anyone know of any good references for this?
Does anyone have an explanation of why aspirin in particular helps tomatoes?

  • Some website references: 1, 2, 3, 4, 5, etc...
  • Sounds like it could be an old wives' tale. However I think it could be a good experiment for a school science fair project! Having judged plenty, having an original idea like this counts for a lot (and no more Vitamin C experiments, thank you!)
    – winwaed
    Jan 23, 2012 at 14:05

2 Answers 2


Salicylic acid is a phytohormone (plant hormone). It was originally extracted from willow bark. It mediates systemic acquired resistance, the reaction of a plant as a whole to a localized pathogen attack.

It's been shown to be effective when sprayed on some plants against some pathogens. There's a book on its role as a plant hormone. I'd get it from inter-library loan - it's a $200 book!

Sounds promising. We had some late blight this year that I would have tried it on to (hopefully) slow the spread.

  • Thanks Ed. The references you and @CuriousGuy provided show that as a plant hormone, Salicylic acid is important and can have an effect applied to the leaves or roots. However, it's still not clear whether it is worthwhile in actual garden situations - there seem to be no references for field trials.
    – Simon
    Feb 18, 2012 at 23:24

A few other references on Salicylic Acid treatment (in plants). If you have a local state university most of these journals should be available as walk-in. Also, if you call the librarian you can often get access with a good story.



I hope this helps.


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