Will Coffee Grounds Kill Grass?

Coffee grounds are used for all kinds of gardening tasks. They can help bring out the color in hydrangeas or provide a complete growing medium for certain types of mushrooms. Many people use spent coffee grounds to boost the acid content in their soil or as a regular source of compostable material and, later, fertilizer. But will coffee grounds kill grass when they are added directly to a lawn with no time to break down beforehand?

Will Coffee Grounds Kill Grass?

No, coffee grounds will not kill grass. Fresh coffee grounds, in small and infrequent doses, should not kill grass and used coffee grounds are even less likely to cause damage.

Spent coffee grounds have a neutral pH of about 6.8 and are a decent source of “green” compost material. They break down to provide soil and established plants with a handful of nutrients including phosphorous, potassium, copper, and magnesium. They also release a small amount of nitrogen as they break down, but not enough to be a good source of nitrogen.

What Will Coffee Grounds Do to a Lawn?

What coffee grounds will do to or for a lawn depends on one very specific factor: are these “used” coffee grounds or “fresh” coffee grounds? Used or “spent” coffee grounds, for example, could be sprinkled directly on an established lawn and allowed to break down there, providing the essential nutrients mentioned above.

Fresh coffee grounds will still provide these nutrient benefits but at a higher cost. Fresh coffee grounds are still full of caffeine. Caffeine isn’t something you want your lawn to have access to. First, caffeine can harm your lawn by tying up nitrogen and other nutrients in the soil. Caffeine can also slow down and poison earthworms and other beneficial insects.

Further, caffeine can prevent seeds from sprouting. For an established lawn, this could seem like a great thing- no more weeds. The thing is, caffeine also makes it hard for sprouts and new growth to thrive. This could mean bald patches appearing in your lawn or a slower recovering time after you mow your lawn.

Related Article: Read More About What Kills Grass

Do Fresh Coffee Grounds Kill Grass?

Plain, dry, fresh coffee grounds are unlikely to kill your lawn in small quantities. However, large quantities of fresh coffee grounds can affect your soil and leave your lawn looking under the weather over time. These negative effects are all caused by the caffeine content in the beans. Brewing coffee removes about 70 to 80% of this caffeine from the beans, making it safer to use on the lawn and in the garden.

Will Used Coffee Grounds Kill Grass?

Used coffee grounds are more beneficial to your compost pile than they will be to your lawn if sprinkled directly onto it. Used coffee grounds have about 20% of the caffeine they had when fresh. While this is still a significant portion and is enough to affect the soil or compost pile it is added to, this effect can be mitigated with water and time.

For example, the best way to use spent coffee grounds as a fertilizer for your lawn is to compost them. Coffee grounds are considered a “hot” or “green” addition to compost as they produce heat when they break down and need to be composted with “cool” or “brown” compost additions such as leaves, bark, or paper coffee filters.

Once added to a compost pile, the coffee grounds should be given the same treatment as the rest of the compost. Coffee grounds should make up no more than half of the “green” component of a compost pile to prevent the caffeine from inhibiting microbial and worm activity. Adding water to the pile at regular intervals can help reduce caffeine levels. After the coffee grounds have been composted, this compost can be safely used to fertilize any type of plant, including your lawn.

Will Spilled Coffee Kill Grass?

Spilled coffee should not kill established grass. Brewed coffee can, however, reduce the germination rate of seeds and weaken seedlings. Brewed coffee is not a good lawn amendment or addition as it is likely to inhibit growth and recovery due to its caffeine content and any potential plant nutrients are more likely to be found in coffee grounds rather than brewed coffee.

How Do You Get Coffee Or Grounds Out of a Lawn

Whether your compost bucket has tipped over at the wrong time or you happened to spill your travel mug on the way to your car, there are several simple ways to clean up and mitigate the effects coffee and coffee grounds have on your lawn.

If dry or damp coffee grounds are spilled on your lawn, the best thing you can do is vacuum or sweep them up. More than anything else, the caffeine found in coffee is the part of coffee grounds that could cause damage. With little liquid, the caffeine is unlikely to leech into your lawn.

For spilled coffee or very wet coffee grounds, the best thing to do would be to flush the area with water to help dilute the concentration of caffeine as caffeine is water-soluble.

Coffee Grounds Can Be a Potent Lawn Fertilizer

Can coffee grounds kill grass? Over time coffee grounds can be a little too good for your lawn and lead to a “burnt” or yellow appearance. With the right amount of time and care, however, you can use those same coffee grounds to help your lawn look green and lush with little additional fertilizer.