Right outside of the garden shed, let me be the first to say that yes, you can definitely use coffee grounds to boost lettuce production in the garden. However, the kind of coffee grounds you use makes all the difference. But first, in the world of Lactuca sativa L. var. capitata, one thing is for sure.
Lettuce leaves need nutrients to grow big and green. If you are planting this green plant indoors or outdoors in a raised bed, using coffee grounds can be a great way to increase yields and even protect against mites and mildew. Learn more about how to use coffee grounds to help grow lettuce, along with how much and when to use this soil additive.
What are Used Coffee Grounds?
Here is a consideration as we start this conversation. The reason why coffee grounds are a popular additive to gardens filled with lettuce plants is due to the plethora of nutrients.
According to the University of Wyoming, “Coffee grounds contain approximately 2 percent nitrogen, 0.06 percent phosphorus, and 0.6 percent potassium by volume. They also contain many micronutrients including calcium, magnesium, boron, copper, iron, and zinc.”
To be considered a fertilizer, a substrate should include nitrogen (N), phosphorus (P), and potassium (K). By supplying all of these at one time, as is the case with used coffee grounds, the material serves as a second-hand fertilizer. As a result, you are getting a free fertilizer that is made from all-natural plant material.
This is certainly safe to eat and use in your plant food, since you drink coffee made from the ground up coffee beans. In fact, coffee shops are known to give away their used coffee grounds to gardeners, so ask around if you are not actually a coffee drinker. You can help a cafe reduce its overhead for garbage and come up with a great fertilizer for your green and red lettuces.
What is the NPK Ratio for Coffee Grounds?
Coffee grounds are on par with a 20-5-5 ratio of NPK. According to Gardening Know How, “The higher the [NPK] number, the more concentrated the nutrients are in the fertilizer. For example, numbers on fertilizer listed as 20-5-5 have four times more nitrogen in it than phosphorus and potassium.
A 20-20-20 fertilizer has twice as much concentration of all three nutrients than 10-10-10.” When you purchase Miracle-Gro or one of the conventional plant foods in a powder or granulated form, it is most commonly lower at 10-10-10 or 8-15-36.
This is an economical and environmentally sustainable way to grow a garden, especially lettuce. As you grow new lettuce plants from seed or seedlings, you can use coffee grounds as a healthy soil additive. Save money on your gardening, and find a new way to get rid of used coffee that would otherwise go into the trash can.
Can I Use Flavored Coffee Grounds for Plant Food?
Another thing to consider is whether you want to use flavored coffee for your plant food. While the addition of flavorings will not change the effect of ground coffee as a plant food, there are reasons why you might not want to use this type of coffee.
Do not use flavored coffee or beans that have been treated with artificial flavorings if you are growing an organic lettuce garden. This can change the quality of the organic plant material and deem it no longer fully all-natural and/or organic.
How to Make Coffee Grounds for Lettuce Fertilizer?
However, you are going to be broke and out of caffeine if you go about using new coffee grounds to make your lettuce plants whistle a new tune. In fact, you do not want to use new coffee grounds at all. If you are thinking about grinding up some whole bean coffee, maybe even that hardcore Death Wish Coffee, for your lettuce, stop right now.
You want to drink the coffee that you brew. After all, that is what coffee is made for–and it’s super expensive. Avoid using freshly brewed coffee as a plant tea, too. You are not going to get the same effect from adding a cup of cold brew to your lettuce plants, as you would from coffee grounds.
Step-by-Step Process of Using Coffee for Plant Food
Step 1: Gather Used Coffee Grounds
Used coffee grounds are the leftover coffee ground up from a brewed pot or cup of coffee. Once you have made a cup of coffee, or a pot, keep your coffee grounds out of the garbage. If you are using a compostable paper filter for your coffee machine, leave the grounds in the filter and place it in a container to let dry out on the counter or on the windowsill.
Otherwise, take the grounds from the coffee machine or after you have brewed a French, Turkish, or Italian style moka press pot of coffee–however you choose to make your coffee. I would not suggest using K-cups for this, as the amount of coffee grounds is negligent per plastic cup. However, you can save this material over time and it will soon add up.
Step 2: Store Used Coffee Grounds
Place the coffee grounds in a clean jar. Store in the refrigerator for up to 48 hours if you are not going to use these right away, so as to avoid mold growth. They can last for a few days in the fridge, but if you want to store used coffee grounds, here’s how. Pour the grounds out on a parchment paper lined baking sheet.
Optional: Baking Coffee to Dry it Out
Turn on the oven to 200 degrees, and then bake the ground coffee beans for 30 minutes, shaking the tray once to shift the grinds around to avoid burning. This will dry out the ground coffee and remove any moisture that would harbor bacteria or attract mites or mold. At this point, allow the coffee to cool completely.
Store in a sealed container and use a tablespoon when adding the coffee grinds to lettuce plants in your garden.
How to Compost Coffee for Lettuce Plant Food?
Interested in composting coffee grounds to be used as plant food for lettuce? You can do this, too. However, you do not have to compost the coffee grounds in order to use them for plant food on your lettuce plants. Simply adding freshly brewed coffee grounds to the soil will do plenty of magic.
If you do compost coffee for lettuce plant food, the total process will take you about 90 days, which is three months. According to Homes and Gardens, “If you don’t have enough green material, the compost pile won’t heat up because the microorganisms don’t have enough energy to do their thing. After about three months your old coffee grounds will have been transformed into nutrient-rich compost giving your plants a much needed boost.”
This requires you to use other plant material to supplement the coffee grounds. Sitting around alone, coffee is too acidic to break down into a composted material. You need to add more fresh plant material, such as the peels from your morning banana and the leftover eggshells rinsed out after scrambling a few for breakfast.
Make sure to avoid adding meat or grease to your compost, as well as any dairy or animal products. These only attract insects and rodents that are harmful to the composting process, and will leave behind maggots and smelly things.
What is Compost Accelerator for Composting Coffee Grounds?
Instead, add lettuce and old vegetable plant material, along with newspaper strips and coffee grounds to a compost bin.
You can also add a supplement that has microorganisms to help break down the material even faster. Compost microorganisms are tiny bugs that are beneficial to soil and the composting process. These are found in compost accelerators available at home and garden supply stores.
A compost accelerator is a soil additive that looks like dirt and contains invisible organisms you cannot see. No worries about long earthworms, here! Instead you sprinkle the compost accelerator onto the compost of coffee grounds and other plant material.
Toss this together and allow the microorganisms to do their jobs. You will have viable compost matter in a month or so that is ready to add to your lettuce plants.
How to Use Coffee Grounds for a Lettuce Garden?
When you are ready to use these coffee grounds for the lettuce garden, all you need to do is sprinkle these directly on the soil. This method of feeding lettuce works in either in a container garden indoors or outdoors in a raised bed or the ground. The coffee grounds can be fresh from the coffee making vessel, or they can be dried out or made into a compost.
Either way makes little difference. Also, there is no use in regrinding these to a specific size for use in a lettuce garden. Whether these are espresso grind beans or beans ground for general brew, they will provide the same percentage of plant nutrients over time.
Use a pronged fork or spade to sift the grounds into the top layer of soil. Avoid getting coffee grounds directly on the lettuce leaves or stem. This can burn the green material due to too much acid. Instead, maintain a small amount of grounds directly in the dirt. Follow by watering the plant thoroughly once you have mixed in the coffee grounds.
Amount of Coffee Grounds to Add to Lettuce
What is the magic formula for adding coffee grounds to lettuce plants? For the best results, Ground by Ground research reports you want to use 2.5 to 10 percent coffee grounds per soil material. That is not very much at all in order to do the trick.
To figure out how much this is per plant, simply add either a quarter teaspoon or up to one teaspoon of coffee grounds to the soil around the plant. Start with the smallest amount if you are concerned about over feeding the lettuce. Give the plant a week to see if there is any change.
If not, add another quarter of a teaspoon up to one teaspoon of coffee grinds. A larger lettuce plant will benefit from up to a teaspoon, while a seedling needs no more than a quarter of one to do the job.
Nutrients in Coffee Grounds for Soil Supplementation
Now let’s get to the nitty gritty of why you want to supplement your soil with coffee grounds in the first place. The answer is to increase the nutrient factor–bottom line. When you have used coffee grounds that have already been run through the coffee pot, you can still get quite a lot of use out of these.
Avoid tossing them out and use coffee grounds in your lettuce to boost various minerals and vitamins. According to Ground to Ground research, scientists have found that coffee grounds increases these levels in lettuce plants:
- Plant chlorophyll by more than 60 percent
- B-carotene by more than 70 percent
- Lutein by 90 percent
As for growth potential, the use of coffee grounds as an all-natural fertilizer adds to the yield of lettuce plants by increasing biomass production.
When do I Add Coffee Grounds to Lettuce Plants?
Add coffee grounds to lettuce plants throughout their plant life as long as you are not using other fertilizers or plant foods. You can burn or kill the plant material with too many nutrients if you are not careful. Get a soil testing kit from the hardware store or plant supply shop to see how much NPK your lettuce plants need before adding coffee grounds.