Do Tomato Plants Like Coffee Grounds?
If you’re looking for a simple way to increase your tomato harvest, you may be considering adding coffee grounds to your soil. While it’s true that coffee grounds contain trace amounts of nutrients that can be beneficial for plants, the risks outweigh the benefits in this case.
In other words, you shouldn’t use coffee grounds to fertilize tomatoes. At best, they won’t provide any significant benefit to your plants. At worst, they could prevent tomato seeds from germinating or seedlings from growing properly.
Coffee grounds aren’t completely useless for gardening applications, however. You just need to know how to use them properly. And that’s exactly what we plan to cover in this guide!
Can Coffee Grounds Be Used as Fertilizer?
Many modern gardeners are concerned about sustainability and looking for ways to use things that would otherwise go to waste. Maybe you’ve heard of using crushed eggshells as a root-strengthening source of calcium. Or banana peels as a potassium booster. But what about coffee grounds?
If you’re a coffee lover, coffee grounds may be in ready supply in your household. Before you start using them as fertilizer in your tomato garden, however, here are some things to consider:
- Coffee grounds only contain trace amounts of nutrients beneficial to plants, like nitrogen, potassium, and phosphorus.
- The caffeine residue in coffee grounds could slow the growth of your plants or keep new seeds from germinating at the proper rate.
- Coffee grounds can take months to break down, so they’re not likely to deliver any short-term benefits when added directly to soil.
- Depending on the type of coffee, the grounds may be very acidic and might affect the pH of your soil in a way that doesn’t benefit your tomatoes.
To summarize, if you’re looking for a way to boost your tomato harvest, adding coffee grounds to your soil probably isn’t the best bet. If you still want to give it a try, keep reading to learn how to do it the right way.
Do Coffee Grounds Deter Pests?
Perhaps you’re not interested in using coffee grounds as fertilizer at all. In some cases, coffee grounds can be an effective deterrent for insect pests. Sprinkling a thin layer of grounds at the base of your plants could help deter slugs, snails, and ants.
But coffee grounds aren’t a universal deterrent—they may not be effective against tomato-specific pests like aphids, hornworms, and tomato fruitworms.
In this case, the potential drawbacks of using coffee grounds outweigh the benefits. Even if you succeed in keeping away a few pests, the coffee grounds themselves could weaken or even harm your tomato plants in other ways. It’s better to use tomato-safe pest deterrents.
Can You Use Coffee Grounds as Mulch?
Another way to potentially use coffee grounds is as mulch. When applied correctly, it can help reduce moisture loss and may even provide some weed suppression benefits. Again, however, the potential benefits of using coffee grounds as mulch may not outweigh the risks.
Because they’re finely ground, coffee grounds compact easily. If you apply them in a layer that’s too thick over your soil, it could prevent air and water from entering the soil. The acidic properties of the coffee grounds could also alter the soil pH and lead to other problems with plant growth.
If you’re going to use coffee grounds as mulch, it’s best to compost it first. Then, apply a thin layer to the top inch or two of soil and rake it in to make sure it’s evenly distributed.
Tips for Using Coffee Grounds with Tomato Plants
The best way to use coffee grounds in your tomato garden is to incorporate them into your compost pile. Combined with grass clippings, leaves, and vegetable scraps, coffee grounds can help you create nutrient-rich compost to use in your garden. Just keep in mind that it can take several months for these things to break down into usable compost.
Here are some tips for composting with coffee grounds:
- Place your compost bin or pile in a well-drained, shady area to keep it from staying too moist or drying out too fast.
- Alternate layers of greens (like grass clippings and food scraps) and brown (like dry leaves, wood chips, and shredded paper).
- Make sure everything you add to the compost pile is as finely chopped or shredded as possible to help it break down more quickly.
- Turn the pile every few weeks to introduce oxygen and water it periodically if it starts to get too dry (it should be just slightly damp, not soaking wet).
- Sprinkle your fresh coffee grounds in as you turn the pile so they become evenly distributed.
If you put some effort into maintaining your compost pile throughout the summer and fall, it should be ready to go in the spring. It doesn’t hurt to test your soil before adding compost, just to make sure you’re getting the right balance of nutrients. When planting season arrives, use your compost to enrich your garden soil as needed.
While compost can be a great addition to any garden, if you want to maximize your tomato harvest, it’s best to use fertilizer formulated specifically for tomatoes. Tomato plants can generally benefit from a balanced NPK fertilizer (nitrogen, phosphorus, potassium) applied several times throughout the growing season. Just avoid fertilizers that contain too much nitrogen, as this can lead to excessive leaf growth at the detriment of fruit formation.
Final Thought: Coffee Grounds Aren’t a Miracle Cure
Whether you’re looking for a low-cost fertilizer or a natural pest deterrent to use on your tomato plants, coffee grounds aren’t the solution. In certain cases they may offer mild benefits, but the potential drawbacks are significant. Your best bet is to use a product specifically designed for tomatoes rather than risk reducing (or even losing) your harvest.
Shop the Park Seed collection of tomato supplies to find everything you need to enjoy a bountiful tomato harvest each and every year.
From organic seed starter and nutrient-rich soil amendments to tomato-safe pest deterrents and fertilizers, Park Seed has it all. Shop now to get your tomato garden off to a healthy start or to make your growing season last a little bit longer.