Question about use of coffee grounds

I put coffee grounds in my compost pile but also add it around my tomato plants.  We drink a lot of coffee  so there is always grounds on hand. Is there such a thing as adding too much around the plants that it would have a negative effect?

The issue that comes to mind is every time you're putting grounds around the pot is that you're acidifying the soil a bit.  So if done at too high a frequency you could acidify the soil past the point that the tomatoes like it and they could suffer as a result.

Keep in mind that there are folks on here who have more years of experience gardening than I've been alive.

amcon2 wrote:I put coffee grounds in my compost pile but also add it around my tomato plants.  We drink a lot of coffee  so there is always grounds on hand. Is there such a thing as adding too much around the plants that it would have a negative effect?

Not really, I use them for mulch as well as in the compost pile.

SwampTroll wrote:The issue that comes to mind is every time you're putting grounds around the pot is that you're acidifying the soil a bit.  
Keep in mind that there are folks on here who have more years of experience gardening than I've been alive.

used coffee grounds have a relatively neutral pH of around 6.5 after coming out of the auto drip coffee maker. https://www.gardeningknowhow.com/composting/ingredients/coffee-grounds-gardening.htm <~~~ click

They've tested pH on grounds and found they have very little effect on pH. I get grounds from Starbucks frequently and I add them to my compost (thought of as a green/Nitrogen), I mix it before planting (quick Nitrogen release with a slow Phosphorus and Potassium release), sometimes make tea out of it, and I also use it as mulch for those dreaded slugs. If you YouTube "one yard revolution slug wars" he has a very interesting video on an experiment he made. I love using free sources in my garden.

Best of luck!


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Thanks for the responses.  I did not know that used grounds would have little effect on the ph. You can always learn something new here! I'm going to continue sprinkling those grounds without worry.

amcon2 wrote:I put coffee grounds in my compost pile but also add it around my tomato plants.  We drink a lot of coffee  so there is always grounds on hand. Is there such a thing as adding too much around the plants that it would have a negative effect?

Do you have roses, azaleas, gardenias, blueberries, redwoods, magnolias, rhodies, hydrangeas? They all love coffee, too. 

I have seen posts on numerous sites that coffee grounds used on the garden can inhibit seed germination, especially seeds such as lettuce.  I have never experienced this, but wonder what others have observed regarding seed germination & coffee grounds.

I lightly spread coffee grounds over the entire raised bed surfaces to deter the neighborhood cats from using them as their bathroom, and that has been very successful. A few weeks ago I planted lettuce & radish seeds among the coffee grounds, and I planted a little heavier than necessary to ensure a good germination of seeds. It appears that every seed I planted germinated, and yesterday I had to thin both the lettuce & radishes so the plants can develop.  Doesn't appear that the coffee grounds affected the germination rate at all.

Anyone done experiments with the effect of coffee grounds on seed germination?

SwampTroll wrote:Keep in mind that there are folks on here who have more years of experience gardening than I've been alive.

I'll trade ya.

Used coffee grounds are also supposedly a good natural snail/slug repellent/pesticide.

ChasingAnnie wrote:They've tested pH on grounds and found they have very little effect on pH. I get grounds from Starbucks frequently and I add them to my compost (thought of as a green/Nitrogen), I mix it before planting (quick Nitrogen release with a slow Phosphorus and Potassium release), sometimes make tea out of it

Anyone else find this ironic?

No_Such_Reality wrote:Used coffee grounds are also supposedly a good natural snail/slug repellent/pesticide.

I've found that to be not true - the slugs crawl right over the grounds to get to what they want to eat. Would be nice if they did, but they don't bother our slgus at all. Diatomaceous Earth stops them, but coffee grounds don't.

ralitaco wrote:

ChasingAnnie wrote:They've tested pH on grounds and found they have very little effect on pH. I get grounds from Starbucks frequently and I add them to my compost (thought of as a green/Nitrogen), I mix it before planting (quick Nitrogen release with a slow Phosphorus and Potassium release), sometimes make tea out of it

Anyone else find this ironic?

! Ralitaco