Routinely pouring leftover coffee on your plants or dumping coffee grounds on them is not a good idea.
However, using leftover coffee once a week and coffee grounds sparingly is beneficial.
That applies to both houseplants and outdoor plants.
The Spruce / Danielle Holstein
If you regularly add coffee or coffee grounds to your plants, keep a close eye on them.
However, there is a difference between plants that prefer slightly acidic soil and.plants that need very acidic soil.
For example,rosesandbeansgrow best in slightly acidic to neutral soil whereasblueberriesneed highly acidic soil to grow.
The Spruce / Danielle Holstein
Coffee grounds contain about 2 percent nitrogen, which is rather low but still benefits plant growth.
Adding large amounts of coffee grounds to the soil as a fertilizer is not recommended.
They work great as a soil enhancer around acid-loving plants and add nutrients to compost piles.
The Spruce / Danielle Holstein
Another way to use liquid coffee is to add it to a dry compost pile to increase moisture.
Only use black, unflavored coffee on your plants.
No, adding coffee grounds directly to the tomato plants is not recommended.
Yes, excess coffee or coffee ground is detrimental to plant growth.
Used Appropriately, Coffee Grounds Improve Soil and Kill Slugs.
Grounds in the Garden.Texas A&M University AgriLife Extension.
