Aspirin Enhances Plant Disease Resistance

An old Urban legend states that adding aspirin to the water in Christmas Trees will help to keep them subtle and fresh. Aspirin contains salicylic acid which is produced by many plants in response to bacterial and pathogenic attacks. Salicylic acid found in aspirin helps prevent the growth of microorganisms.

Being an acid it also works with other compounds found in aspirin to acidify the water. Unfortunately the combined acids in aspirin appear to actually have an overall negative impact on the longevity of the cut tree and may actually expedite drying and needle drop.

Aspirin when applied to a damaged plant (such as a christmas tree) will “inhibit the response to injury or to treatment ” 

A study done on tomato plants found that Aspirins salyicylic acid and related hydroxybenzoic acids when sprayed on already damaged plants actually expedites the plants demise. This is perhaps why aspirin added to Christmas tree water actually expedites the trees preordained decay. [ The wound response of tomato plants can be inhibited by aspirin and related hydroxy-benzoic acids ]

Aspirin for Tomato Plants

Some gardeners believe that aspirin dissolved in water as a foliar spray will actually help plants fight off diseases and increase yields. Soaking the seeds in aspirin water before sewing them is another method that is used.

Several studies indicate that the aspirin – tomato scenario is more than an Urban legend – it works. Adding it to the irrigation water will have little impact unless it sprayed directly on the foliage for absorption by the plant.

Aspirin water is highly effective in preventing several forms of blight. Fusarium and verticillium are the two most notable, both plant diseases will have devastating effects on tomatoes and most other garden crops as well. The diseases are much more common following heavy rains.

As per James Wong, of the BBC, plants should be dosed with a water-based aspirin solution when heavy rain is looming in order to enhance the plants resistance. Naturally a heavy rain will wash the solution away so a post storm spray is also advisable. 

A US Department of Agriculture study determined that the use of a home made aspirin spray, resulted in a nearly 50 % reduction in blight. The Salicylic acid in aspirin enhances the plants resistance against microbial as well insect attack. As per the study published in the Annals of Applied Biology – [ Priming Plant Defenses with Aspirin-like Compound ] The salicylic acid in aspirin is effective in fighting disease in the nightshade family, which also includes peppers, eggplant and potatoes.

An aspirin spray also induces resistance to tobbaco mosaic virus in susceptible plants – [ Acetylsalicylic acid (aspirin) induces resistance to tobacco mosaic virus ]


In addition to nightshade family plants the use of aspirin has also been found to enhance stress tolerance in Beans and legumes – See Acetyl salicylic acid (Aspirin) and salicylic acid induce multiple stress tolerance in bean and tomato plants


In corn/maize salicylic acid and benzoic acid also found in aspirin could provide protection against stress from low temperatures. [ Journal Maydica 2000 Vol. 45 No. 1 pp. 29-33  ] However, it was also found that under the plant’s normal growing temperatures it could actually be harmful – so it is advisable to avoid this practice during the normal growing season so far as corn is concerned.

Gorgan University of Agricultural Sciences in Iran found salicylic acid to be a potent plant hormone which increases yields substantially. Soaking the seeds prior to sewing or foliar spray of the aspirin solution led to enhanced growth, and yield as well as a higher vitamin C content of the produce.

Researchers at the University of Rhode Island, suggest adding 250 to 500mg of aspirin to around 4.5 liters of water and spraying plants several times a month. It is effective in preventing the bilghts and in halting their progress in the early stages. It will not cure full blown infestations.