Coffee grounds are used by hobby gardeners worldwiderecommended for a range of gardening problems. From fertilizing to mulching to pest control, there seems to be nothing a spoonful of used coffee grounds can't do. But can you also fertilize tomatoes with coffee grounds? We'll explain to you how to use the home remedy so that it doesn't harm your tomato plants.
How do coffee grounds help tomato plants?
Coffee grounds provide good amounts of important nutrients, all needed for healthy growth, and should further benefit tomatoes by:
- increases the nutrient content
- balances the pH value
- the ground temperature stabilizes
- increases water storage
- Reduces harmful bacteria and fungi
- germination improved
- the growth rate increases
- promotes earthworm activity
- serves as a natural and organic insecticide
- Weeds reduced
The most important nutrients that you add to the soil with coffee grounds are:
- Nitrogen
- Phosphor
- Magnesium
- copper
Since nitrogen and phosphorus are two of thethree main nutrients for plants(the other is potassium), coffee grounds are a great way to fertilize your tomato plants. While nitrogen content can vary, it is often the most valuable nutrient in coffee grounds.
There is also evidence that coffee grounds are good forEarthworms and compost wormsis, which in turn contributes to soil improvement.
Additionally, research suggests that the natural bacteria and fungi found on decomposing coffee grounds reduce harmful fungi and even prevent them from establishing themselves in the soil of tomato plants.
After all, coffee grounds can toobe used as a natural insecticide. The reason for this is the caffeine it contains. Typically, insecticides have harmful effects as they also kill beneficial worms and pollinating insects, but coffee grounds are a much safer and natural alternative. For example, there is some evidence that coffee grounds attract insects such as ants,Repels snails and slugs.
However, there is still debate about the science on this topic, as some believe that the caffeine is gone after brewing coffee and others say that there is still a lot left in the coffee grounds.
Do coffee grounds make soil acidic?
Tomatoes are an acidic food, so it's no surprise that they like slightly acidic soil. Tomato plants prefer a soil pH between 6.0 and 6.8, while a neutral pH is measured at 7.0.
Scientists disagree about whether coffee grounds make the soil acidic. In short, unused coffee grounds are acidic, but most of the acidity is lost during brewing. This means that the used coffee grounds only have a slightly acidic pH value of 6.5-6.8. However, since this pH is right in the range of what tomato plants prefer, coffee grounds prove to be a great addition to the soil.
The pH of soil treated with coffee grounds increases in the first three weeks and then slowly decreases. For this reason, it's a good idea to check the soil pH every few months.
How to use coffee grounds as tomato fertilizer
There are basically three ways to use used coffee grounds as fertilizer or soil conditioner for your tomato plants:
- You can spread it directly on the floor
- mix with mulch
- compost it first
Basically you can add the coffee grounds directly to the soil of your tomato plant. But coffee powder can easily clump when used in large quantities, blocking air and moisture from reaching the grounds. That's why it's best to mix the coffee grounds with mulch or compost them first. Leaves, bark and pine needles can be used as mulch for tomato plants.
Spread a 1.5-centimeter-thick layer of used coffee grounds around the base of your tomato plants and cover with 5 to 8 centimeters of organic mulch.
Another way to fertilize tomatoes with coffee grounds is to sprinkle 1 cup of used coffee grounds around the base of your tomato plant and work it into the top 2 to 3 inches of soil with a trowel or subtractor. This stimulates the decomposition of the coffee grounds and prevents problems with soil compaction.
If you compost the coffee grounds first, you can add them to the compost pile in the fall so they are ready to use in the spring. You should pay attention to three things:
- Coffee grounds should not make up more than 20% of the total compost.
- Allow 2-3 months for it to decompose before applying it to your garden.
- Apply the already finished compost to the soil of your tomato plants in a layer of 2 to 5 cm.
No matter which method you choose, the important thing is: Do not let the coffee grounds (or compost) come into direct contact with the tomato plant. The same goes for mulch. You should leave at least 2 centimeters of space between the coffee grounds and the bottom leaves. That's because coffee grounds and compost can cause mold, and their high nutrient content can chemically burn the plant.
How much coffee grounds should you use on your tomatoes?
While coffee grounds are great for soil and compost, they can also be overkill. You should use coffee grounds in moderation. The high levels of nitrogen and potential caffeine can unbalance the soil or compost if used in excess.
Limit the amount of coffee grounds in your compost to a maximum of 20 percent. Coffee grounds are considered green material, such as fresh grass clippings and kitchen scraps, and must be mixed with brown material, such as dried leaves. You can learn how to compost properlyread here.
For a standard compost heap measuring 90 x 90 x 90 cm, this means no more than 570 cups of used coffee grounds. As you can see, it would be quite difficult to exceed this limit.
90 x 90 x 90 cm = 0.72 cubic meters
20% of this is 0.144 cubic meters
Since 1 cubic meter = 4000 cups, that's about 570 cups of coffee grounds
You can use the coffee grounds when you plant the young plants outdoors and then 1-2 times a month. Typically, most plants prefer fertilizer in their growing season, just before they bear fruit, but any other time works well.
Be careful not to use too much coffee grounds as this will affect the frequency of use. Check your soil pH regularly.
This is how you can fertilize tomatoes with coffee grounds:
- Add the composted coffee grounds to the planting hole to improve the soil composition. It will act as a long-term fertilizer and provide nitrogen to the soil for several weeks.
- Mulch tomatoes with composted coffee grounds (or coffee grounds + mulch) throughout the summer to retain moisture in the soil, prevent weeds, and add nutrients to the soil.
- Work the coffee grounds into the ground in the fall and let them decompose directly in the ground. Experts recommend enriching the soil twice a year with organic material such as compost, manure or coffee grounds.
- For tomatoes in a pot: Mix the coffee grounds and soil in a 1:1 ratio and add the mixture to the pot so that the soil is completely covered. Always allow the coffee powder to dry out thoroughly before use to avoid mold formation.
