If you’re a coffee drinker, you might be wondering what plants benefit from coffee grounds. That pile of used grounds from your morning brew doesn’t have to go in the trash. It can be a fantastic, free resource for your garden, offering nutrients and improving soil structure for certain plants. Let’s look at how to use them correctly and which plants will thank you for the extra treat.
What Plants Benefit From Coffee Grounds
Coffee grounds are considered a “green” compost material, rich in nitrogen. They also contain smaller amounts of potassium, phosphorus, and other minerals. When used properly, they can acidify soil, attract beneficial worms, and even help suppress some fungal diseases. However, they aren’t a good fit for every plant, and misuse can cause problems.
Plants That Love Coffee Grounds
These plants thrive in the slight acidity and nitrogen boost that coffee grounds provide. They are the best candidates for direct application or inclusion in compost.
- Acid-Loving Shrubs: Azaleas, rhododendrons, and camellias adore acidic soil. Lightly worked-in coffee grounds can help maintain the low pH they need.
- Berries: Blueberries, strawberries, and raspberries perform best in acidic soil. Coffee grounds can help you achieve that condition naturally.
- Flowers: Roses, hydrangeas (for blue blooms), and marigolds. The nitrogen promotes lush foliage and blooms, and grounds may help deter slugs around marigolds.
- Vegetables: Tomatoes, carrots, and radishes appreciate the nitrogen and improved soil texture. Many leafy greens like spinach also benefit.
- Houseplants: African violets, snake plants, and philodendrons can benefit from a sparse sprinkling mixed into their potting soil.
How to Prepare and Apply Coffee Grounds
You should never just dump wet, fresh grounds in a thick layer around plants. This can create a water-resistant mat, promote mold growth, and overly acidify the soil. Follow these simple steps for success.
Step 1: Collect and Dry
Spread your used coffee grounds on a tray or baking sheet to dry. This prevents them from going moldy before you use them. Stored them in a container once completely dry.
Step 2: Choose Your Method
There are three main, safe ways to use coffee grounds in your garden:
- Add to Compost: This is the best and safest method. Mix grounds into your compost bin, balancing them with “browns” like dried leaves or cardboard. They’ll break down into a rich, balanced humus.
- Use as a Soil Amendment: Mix a thin layer (no more than half an inch) of dried grounds into the top few inches of soil before planting or around established plants. Do this sparingly, once or twice a season.
- Make a “Coffee Ground Tea”: Steep a cup of used grounds in a five-gallon bucket of water for 1-2 days. Strain and use the liquid to water your acid-loving plants for a gentle nutrient boost.
Plants to Avoid Using Coffee Grounds On
Not all plants want this acidic treat. Using grounds on these plants can hinder their growth or even harm them.
- Seedlings and very young plants, as the caffeine and acidity can stunt growth.
- Plants that prefer alkaline (sweet) soil, like lavender and clematis.
- Some clovers and geraniums may not respond well to the acidity.
Common Mistakes and How to Avoid Them
Even with good intentions, it’s easy to make a few errors. Here’s what to watch out for.
Using Too Much, Too Often
Excess coffee grounds can make soil too acidic and create a compacted barrier. Always use them in moderation. A little goes a long way in the garden, and its better to use to little than to much.
Applying Thick, Wet Layers
Wet grounds clump together, blocking air and water from reaching plant roots. Always dry them first or mix them thoroughly into the soil.
Forgetting to Balance with “Browns” in Compost
In your compost pile, coffee grounds are a “green” nitrogen-rich material. If you add to many without enough carbon-rich “browns” (like dried leaves, straw, or paper), your pile can become smelly and slimy. Aim for a rough mix of about 1 part greens to 3 parts browns.
Additional Benefits in the Garden
Beyond plant food, coffee grounds have other clever uses. They can be sprinkled lightly around plants to deter slugs and snails, who dislike crawling over the gritty texture. Some gardeners also find they repel cats from using garden beds as a litter box. Worms are attracted to coffee grounds, so adding them to a vermicompost bin or your garden soil can encourage these beneficial soil aerators.
FAQ: Your Coffee Ground Questions Answered
Can I use coffee grounds on all my plants?
No. Focus on acid-loving plants like blueberries, azaleas, and roses. Avoid using them on plants that prefer alkaline soil or on seedlings.
Are used coffee grounds better than fresh?
Yes, always use brewed grounds. They have less acidity and caffeine, making them safer for plants. Fresh, unbrewed grounds are to strong.
How often should I add coffee grounds to my garden?
For in-ground application, once or twice per growing season is sufficient. In compost, you can add them regularly as you have them, as long as you balance with browns.
Do coffee grounds fertilize plants?
They are a slow-release source of nitrogen, which is a key fertilizer nutrient. They are not a complete fertilizer but are a excellent soil amendment.
Will coffee grounds change my hydrangea’s color?
Yes, for varieties that can change color. Coffee grounds can help lower soil pH, encouraging blue blooms in bigleaf hydrangeas. For pink blooms, you need alkaline soil.
Using coffee grounds in your garden is a simple way to recycle kitchen waste and improve your soil naturally. By knowing what plants benefit from coffee grounds and following the right steps, you can give a select part of your garden a healthy, free boost. Just remember the golden rule: always use them in moderation and prepare them properly for the best results.