Most of us toss our used coffee grounds into the compost bin without a second thought once we’ve had our morning caffeine fix. But hold on a second! Those leftover grounds are actually a goldmine of nutrients for your garden. If you’re a fan of vibrant, bushy geraniums, you’ll be happy to know that they absolutely love a little coffee boost.
What’s actually inside those coffee grounds?
Even after brewing, coffee grounds retain a ton of trace elements and minerals that plants crave. From a gardener’s perspective, there are three big players hiding in your filter:
- Nitrogen
- Phosphorus
- Potassium
Think of nitrogen as the “growth engine”—it’s what helps your plants push out those lush new stems and leaves. Potassium is the secret to that deep, healthy green color; it keeps your foliage from looking pale or turning yellow. Finally, phosphorus is a must-have for flowering plants because it fuels bloom production. This combo makes coffee grounds a fantastic, budget-friendly fertilizer for geraniums in window boxes or garden beds.
Step one: Collect and dry your grounds
If you’re a daily coffee drinker, you’ll have a steady supply in no time. However, don’t just dump a wet filter directly onto your plants! Not only is one day’s worth usually not enough for a full feeding, but wet grounds can get moldy very quickly. It’s much better to collect and dry them before treating your geraniums to a weekly snack.
- Spread the grounds out on a large plate.
- Flatten them out so they dry faster.
- Place the plate in a warm, dry spot.
- Once they’re bone-dry, store them in an airtight container.
- Keep them in a dry place until you’re ready to garden.
How to feed your geraniums with coffee
When you’re planting or repotting your geraniums in the spring, they need a solid nutrient boost to kick off the growing season. You can mix a healthy portion of dried grounds directly into the potting soil right from the start.
During the peak growing season—which lasts all the way until the first frost—you should aim to fertilize about once a week. Just sprinkle the dried grounds around the base of the plant and gently scratch them into the soil. Alternatively, you can add grounds to your watering can (about 1 tablespoon per 2.5 gallons of water). Just be careful to water at the soil level; getting the leaves and stems too wet can make your geraniums more vulnerable to diseases and pests.
Pro Tip:
Geraniums are “heavy feeders,” meaning they have a big appetite for nutrients, especially during their blooming period. If you only produce a small amount of coffee grounds at home, make sure to supplement with another fertilizer to keep them happy and blooming all summer long!