In the past we’ve talked about what effect coffee grounds can have on plants, but we haven’t discussed whether coffee grounds can make good fertilizer for vegetable plants, especially tomato plants.
There is a lot of information out there about how to properly fertilize your tomato plants and what products to use for the best results, but will coffee grounds will improve the success of your tomato plants?
The honest answer is, maybe.
I know that’s not what a lot of people like to hear, but it’s the truth. While there hasn’t been any scientific proof that coffee grounds will improve the rate of growth or number of tomatoes your plants produce, there is some scientific data that backs up the reasoning for why people believe that coffee ground are good for tomato plants.
Tomato Plants Like Slightly Acid Soil
The main reason that this idea that coffee grounds can help to fertilize your tomato plants is that tomato plants thrive in slightly acidic soil. Used coffee grounds can help soil become slightly more acidic when they are used as fertilizer.
Now, when we say slightly more acidic, we do mean slightly.
In some cases, coffee grounds could actually be alkaline or neutral meaning they are not acidic and therefore not helping the plants, but in most cases the grounds are just acidic enough to help the soil, but not by much.
Coffee grounds contain around 2% nitrogen as well as varying amounts of phosphorus and potassium which are all very important for the growth of tomato plants. By mixing some coffee grounds into the soil below your tomato plants you’re introducing these nutrients that the plants need to thrive.
However, coffee grounds do not act like traditional fertilizer and will take some time to affect the soil enough to help the plants. In fact, it may have the opposite effect on the soil for a couple weeks before releasing enough of the nutrients in the soil to help.
This is why people claim that coffee grounds help out with tomato plants over the long run, but not necessarily during the up front growing. So, keep that in mind if you’re looking for something to help get your plants growing quickly.
Should You Use Coffee Grounds to Fertilize Tomato Plants?
Knowing the information above, there’s nothing wrong with using some of your used coffee grounds to help fertilize your tomato plants, but don’t expect some miracle growth hack to come from it. You also need to make sure that you’re not overdoing it by using too much on your plants.
Take about 1 cup of used coffee grounds spread around the base of your tomato plant and work it into the top 2-3 inches of the soil. This will help the coffee grounds break down and start to release the nutrients into the soil.
You can also use coffee grounds in a compost bin and then use that compost as fertilizer to help the plants grow. Just make sure that you keep the coffee grounds to less than 20% of the compost material as you don’t want to make the compost too acidic. This can be more harmful than good for the tomato plants.
Traditional Fertilizer vs. Coffee Grounds
If you’re looking for a fertilizer to help improve your tomato plants in the best way possible, and you’re open to using store bought fertilizer, there are options out there that are specifically designed for these types of plants and will most likely offer greater benefits than coffee grounds would.
If you would rather not use those types of fertilizers though, used coffee grounds are a great, natural, way to help create a more suitable soil for the tomato plants to thrive in.
Coffee grounds can be very useful when it comes to gardening, but it’s important to understand why plants may benefit and how to properly use them to achieve the best results possible.
FAQs
Compost for tomatoes – When mixed with leaves or sawdust, compost made with coffee grounds provide essential nutrients for tomatoes while combating fungal diseases. Incorporate compost into the soil or use as mulch around tomato plants.
How often should I put coffee grounds in my tomato plants? ›
Avoid Excessive Application: Remember to use coffee grounds in moderation. While they can be beneficial for tomato plants, applying too much at once can lead to issues with soil pH and nutrient imbalances. A thin layer of coffee grounds spread around the base of the plant is typically sufficient.
Do tomatoes like eggshells and coffee grounds? ›
The coffee grounds also have trace amounts of phosphorous and potassium. Eggshells provide calcium to the plants they are placed near. Calcium is especially valuable for tomatoes.
Which vegetables do not like coffee grounds? ›
Coffee grounds inhibit the growth of some plants, including geranium, asparagus fern, Chinese mustard and Italian ryegrass. Conversely, grounds (used as mulch and compost) improve yields of soybeans and cabbage.
How much coffee grounds should I give my plants? ›
We recommend using about a teaspoon of coffee grounds per gallon of water. Let the coffee grounds and water mixture steep for a few nights, stirring occasionally, then strain the liquid through a cheesecloth. The remaining liquid can be used to water, and gently fertilize, your houseplants.
Can I just sprinkle coffee grounds on plants? ›
Are coffee grounds good for plants? Coffee grounds are an excellent compost ingredient and are fine to apply directly onto the soil around most garden plants if used with care and moderation. Coffee grounds contain nutrients that plants use for growth.
Do you put coffee grounds on plants wet or dry soil? ›
Only composted coffee grounds should be mixed into the soil, as fresh grounds will have a higher acid and caffeine content which may burn plant roots. Make sure that grounds aren't too wet to discourage possible mold.
Do cucumbers like coffee grounds? ›
What Vegetables Like Coffee Grounds? Coffee grounds as a fertilizer can be used when growing vegetable crops such as potatoes, cucumbers, peppers, carrots, radishes, and beans. Root crops need magnesium and potassium, while nitrogen is indispensable for green crops.
Why do tomatoes not like coffee grounds? ›
Caffeine Residues: Coffee grounds contain traces of caffeine, which can inhibit the growth of certain plants. While tomatoes are not particularly sensitive to caffeine, the presence of it in the soil can affect the surrounding soil ecosystem, potentially impacting other plants and microorganisms.
What is the best fertilizer for tomatoes? ›
Some growers prefer to use a high-phosphorus fertilizer, indicated by a larger middle number. You can also keep things simple with a fertilizer especially formulated for tomatoes – usually with a ratio like 3-4-6 or 4-7-10. Most importantly, don't over-fertilize.
However, there are some plants that you should avoid using coffee grounds on. Plants that prefer alkaline soil, like lavender and lilacs, can be harmed by the acidity of coffee grounds. Plants that are sensitive to caffeine, such as geraniums and some herbs, can also be affected by the presence of coffee grounds.
What bugs hate coffee grounds? ›
Repel insects and pests:Coffee grounds contain compounds that are toxic to many insects. You can use your coffee grounds to repel mosquitos, fruit flies, beetles and other pests. To use coffee grounds as an insect and pest repellent, simply set out bowls of grounds or sprinkle them around outdoor seating areas.
Can too much coffee grounds hurt plants? ›
Excess coffee grounds, if applied to the soil before composting, have multiple effects on the soil system. In addition to microorganisms tying up nitrogen temporarily, the caffeine residues in the spent coffee grounds can suppress germination and slow the growth of some plants.
How do you fertilize tomatoes with coffee grounds? ›
You also need to make sure that you're not overdoing it by using too much on your plants. Take about 1 cup of used coffee grounds spread around the base of your tomato plant and work it into the top 2-3 inches of the soil. This will help the coffee grounds break down and start to release the nutrients into the soil.
Can I use leftover coffee to water plants? ›
To use coffee as a plant fertilizer, you'll need to dilute it. It should look like weak tea. If you aim for about 1/4 coffee and 3/4 water, or even a half-and-half mix, in your solution (depending on how strongly you brew your coffee), that's about right, but you don't have to be fussy about it.
How often can you use coffee grounds as fertilizer? ›
Frequency does not matter as much as amount. You shouldn't sprinkle more than a thin layer around your plants, or else the coffee grounds can become impenetrable, preventing water from getting into the soil. If you evenly sprinkle coffee grounds around the plants once a week or so, the amount will likely be okay.
Can plants get too much coffee grounds? ›
Excess coffee grounds, if applied to the soil before composting, have multiple effects on the soil system. In addition to microorganisms tying up nitrogen temporarily, the caffeine residues in the spent coffee grounds can suppress germination and slow the growth of some plants.
How often should you give your plants coffee water? ›
A good rule of thumb is to feed and water your plants once a week with a weak coffee solution. They'll appreciate the additional nutrients, as well as the water. And while we're here, let's talk for a minute about those leftover coffee grounds as well.
