If you like plants and are a coffee drinker and haven’t yet connected these two interests, it’s time to learn how you can use coffee grounds in the garden to benefit your soil.
Coffee Grounds as a Soil Conditioner
Coffee grounds break down into a soil-enriching substance to improve the soil’s structure. Some of the ways soil can improve after the addition of coffee grounds to the garden include:
- Improved soil drainage.
- Improved soil texture.
- Increased minerals such as calcium and magnesium.
Coffee Grounds as Plant Fertilizer
Coffee grounds can provide essential nutrients that plants need to thrive. They have at least a little of each of the nutrients provided by chemical fertilizers: nitrogen, potassium and phosphorus.
Coffee grounds won’t release these nutrients instantly. Instead, the nutrients become available as the grounds break down, making them like a supplemental time-release fertilizer.
Applying Coffee Grounds in the Garden
Use biodegradable materials, such as spent coffee grounds, to improve the soil in landscape beds and vegetable or flower beds. Coffee grounds have special characteristics that make them more suitable in some situations than others.
For example, coffee grounds tend to have high nitrogen levels. But they also have low phosphorus and potassium levels compared to a typical fertilizer. Fertilizers that are relatively high in nitrogen tend to encourage bushy leafy growth at the expense of flowers and fruit.
If you need flower or fruit production from plants, apply a small amount of coffee grounds. Instead, use the coffee grounds as an extra boost for plants that need to get big and bushy.
Applying Coffee Grounds to Indoor Plants
Houseplants have a much smaller amount of soil to draw from than outdoor gardens. And some indoor plants, such as tropical plants or young plants, may be very sensitive to changes in their routine. So when introducing a new substance to the soil (such as coffee grounds), start out slowly to avoid any negative impacts.
Coffee Grounds for Acid-loving Plants
The acidity level of coffee grounds can vary based on details like how you prepare your coffee, but grounds tend to be acidic in general. Choose plants that love acidic soil when dispensing your grounds. Here is a list of common acid-loving plants for your edibles garden or landscape:
- Fruits such as cranberries, elderberries, blueberries and gooseberries.
- Vegetables like sweet corn, peppers, potatoes, radishes and turnips.
- Herbs such as thyme, rosemary and oregano.
- Ornamental shrubs such as azaleas, hydrangeas, rhododendrons and camellias.
- Trees such as willows, oaks and magnolias.
Use a soil pH test kit to check the acidity or alkalinity of your soil. This can help ensure you’re keeping the soil pH within the preferred range for each plant.
You can also rinse your coffee grounds before using them to make them less acidic. Or combine them with a more alkaline soil amendment such as wood ash to balance the pH before using.
Tips for how to use coffee grounds in a safe and beneficial manner.
1. Use Coffee Grounds as a Soil Conditioner
Start out by using a small amount of coffee grounds as a supplemental soil amendment or soil conditioner for your plants. This could mean mixing a small amount in with your houseplant mix when you repot a plant, for example. Or you can sprinkle a few grounds on the soil’s surface and then cover them with mulch.
Even for an acid-loving plant, don’t add more than one-quarter coffee grounds to a soil mix. And when starting out, use an even smaller amount.
2. Don’t use too many coffee grounds on each plant
Use caution when applying coffee grounds. Overdoing it could be detrimental, especially for plants that don’t love acidic soil or caffeine. If you’re not sure how your plant will react, err on the side of caution.
3. Use coffee grounds in compost
After applying coffee grounds to all your acid-loving plants, you can compost the rest of your grounds. Some gardeners consider this the ideal way to use grounds in your garden.
Because of their nitrogen content, coffee grounds count as “green” material and need to be balanced with “brown” material (like paper or straw). Use the resulting compost as a soil amendment.
These basics can help you use coffee grounds as a source of nutrients and soil conditioner. Remember to start slow, and if your plants are sensitive, compost your coffee grounds before applying. If you’re new to composting check out our Compost Tips for Beginners to get you off to a good start.