Are Coffee Grounds Good For Tomato Plants?

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Many people have become fond of putting coffee grounds on plants as a mulch or fertilizer, claiming that the coffee grounds are an excellent tonic for their garden. 

While it is true that many plants can benefit from applying nutrient-rich coffee grounds, some plants do not benefit from the coffee grounds and can actually be harmed by adding them. For example, tomatoes do not benefit much from coffee grounds, and there are better sources of nutrients.

Coffee Grounds for Tomato PlantsPin

How Might Tomatoes Benefit From Coffee Grounds?

Coffee grounds contain all the vital nutrients plants crave, including:

  • Phosphorous
  • Magnesium
  • Potassium

In addition, coffee grounds contain some nitrogen and trace elements that plants require, such as:

  • Copper
  • Zinc
  • Calcium

Tomatoes are heavy feeders and need lots of nutrients from fertilizer. Theoretically, this should add up to an excellent fertilizer for tomato plants.

Why Don’t Tomatoes Benefit From Coffee Grounds?

Coffee grounds are made of organic material, so they must be decomposed for the nutrients to become useful to the tomato plants. 

This can be sped by ensuring that the coffee grounds are ground finely before adding them to the soil or soaking the spent coffee grounds to make a nutrient-rich liquid. 

The better practice, though, would be to put the coffee grounds into the compost bin along with the rest of the vegetable waste and allow them to decompose into humus which can be used to improve the soil. 

Any benefit derived from solid coffee grounds will be realized only slowly, and most gardeners wish to give their tomato plants a boost right away.

If you wish to feed your tomato plants quickly, use a fertilizer specially compounded for potato or tomato plants and apply it according to the directions.

If you wish to provide your tomato plants with slightly more acidic soil, coffee grounds are acidic, but they will only work to acidify the soil slowly. 

Once again, the grounds must decompose before they release any benefit to the growing tomato plant. A better approach would be to test the soil for its pH level and amend it using commercially available products.

What Can Be Used To Help Boost Tomato Plants?

Here are better materials you use to provide sources of nutrients to boost tomato plants.

Wood Ash

  • Wood ash is rich in calcium and can remedy any calcium deficiency in plants. 
  • Boil 5 ounces of ash in 2.5 gallons of water for 30 minutes, and then allow the mix to cool to room temperature. 
  • Use this mixture to water your plants. This treatment should be applied at most once every other week.

Epsom Salts

Epsom salts contain magnesium. If your soil has a magnesium deficiency, and you wish to boost the level of your tomato plants, Epsom salts dissolved in water can provide a quick fix if used sparingly. 

For tomatoes, mix two tablespoons of Epsom salt per gallon of water, and use this mixture to water your plants once a month. 

If you wish to apply the Epsom salt directly to the ground, no more than 1 cup should be applied per 100 square feet (an area of 10×10 feet) before transplanting your tomato seedlings. 

If the leaves of your tomato plants turn yellow, this may be a sign of magnesium deficiency, and you can repeat the application.


Many gardeners swear by aspirin for their tomato plants. Aspirin contains salicylic acid, which plants use for their immune system. 

While it won’t kill pests directly, salicylic acid can help improve a plant’s resistance to disease and pests and its drought tolerance. 

Some studies show that it helps improve yield in tomato plants as well. One 250 mg tablet dissolved in a gallon of water and applied when the plants are transplanted ample dose. Too much will have a negative effect, so stick to the ratio.

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