Last year, I moved into a new home and found myself with a personal gardening space for the first time in my life.
I got some lofty ideas right off the bat. I wanted bright colors and lush greens, plants of varying heights and textures, flowers to attract hummingbirds and butterflies, maybe even some edible vegetation.
I invested a hefty chunk of change in this endeavor and dug right in, thinking there was no way I could go wrong. My yard got lots of sunlight; I'd chosen plant species that were well-suited to my hardiness zone; I had plenty of water, all the right tools, and fertilizer; most importantly, I thought, I had a strong nurturing instinct. What else could I need?
The answer, as it turned out, was that I needed to understand what was going on with my soil. I didn't, but the plants I'd purchased sure did, and they did not approve of the situation.
A friend with superior gardening experience recommended that I test my soil's pH level, and once I discovered that my soil was highly alkaline, I asked him if there was anything easy (and not too expensive) that I could do to lower the pH and inspire something, anything, to thrive in my yard besides invasive weeds.
"Sure!" he said easily. And to my utter astonishment, he suggested using something I already had in my home. Something I had been carelessly throwing out with the garbage daily, for months on end. Something that I would never have imagined could stimulate any kind of growth.
This suggestion ended up transforming my backyard from a wasteland into a little slice of paradise. I started using my leftover coffee as fertilizer, and I've never looked back.
Why Coffee is Good for Plants
I used to think gardening was as simple as giving nature some room to do its thing. Scatter some seeds, add a little water, let the sun bake it for a few weeks, and voila: growth! After all, plants that grow in wild, untended spaces certainly make it look that easy.
In truth, though, successful gardening is a science, as well as an art form. Every patch of soil has a pH level that will determine how easily plants will grow (or wither and die) within it. And every plant species has its own requirements for soil acidity, sun exposure, moisture levels, and nutrients. Successful gardening is all about finding and maintaining the delicate balance that meets all of your plants' needs.
Coffee is acidic, so by mixing grounds or watered down coffee into your soil, you can raise its acidity level. Some popular plants go wild for highly acidic soil. For instance, African violets, which are notoriously finicky plants, do quite well in soil that is enhanced with coffee grounds.
Coffee grounds also contain nitrogen, which is an important plant nutrient. People who grow tomatoes and roses, for example, often find great success by using coffee grounds as fertilizer. When coffee grounds decompose, they release nitrogen, working to maintain the ideal temperature for growth in the soil.
This same temperature that aids in growing desirable plants also works to stop weed growth in its tracks, preventing them from robbing your plant babies of valuable water, sun, and nutrients.
Beyond the chemical benefits, coffee grounds also help with physical matters like drainage and aeration when mixed into soil. Plants need their water, but they can be awfully picky about how much and how long they want to soak it in. Coffee grounds will help to manage these processes organically.
Brewed coffee, meanwhile, contains potassium and magnesium, both of which are essential macronutrients for plant growth. This is why some choose to add leftover coffee when they water their house plants.
How to Use Coffee in your Garden
Coffee grounds should be mixed in with soil and fertilizer, not used as the primary base for plant growth. Your plants may like some acid, but too much might make them sick or even kill them.
Determining how much to use will require you to do some research, and maybe some experimentation, learning through trial and error. Doing a quick google search on any plant species, you'll be able to find information on its acidity preferences.
Plants like blueberries, for example, love acidic soil, but for a species like lavender, too much acid can be a death sentence. Too much caffeine can also be a threat to plant growth. When in doubt, err on the side of caution, adding a small amount of coffee to your soil and waiting to see positive results before going further.
Coffee grounds also make a great addition to your compost bin. They'll heighten the acidity and nitrogen levels while also working to keep the material from drying out. They're also believed to help maintain the ideal temperature for composting processes.
It's best to use organic coffee beans when growing edible plants. It isn't necessary to break the bank on expensive brands you wouldn't normally drink--store-bought fertilizer would be preferable, in that case--but you should avoid using chemically processed or flavored beans, as they're more likely to hurt than help.
If you want to use brewed coffee in your gardening efforts, be careful not to overdo it. Some plants will appreciate its acidity more than others, and those that are more sensitive to low pH levels might do best with just a small dose of coffee, once a week or less.
Pay attention to the visible feedback your plants give you, too; if you see yellowing or browning in the leaves after starting them on a coffee regimen, this may be an indication that the acidity is too strong for them. You can either water the coffee down with tap water before pouring it over the soil or stop using it entirely. Luckily, your plants won't suffer from caffeine headaches or other withdrawal symptoms if you cut them off!
Furthermore, be sure to use cold coffee, as a hot cup of joe might actually kill living organisms in the soil that would otherwise work in your favor. You don't want to feed your plants with cream or sugar, and sugar substitutes should be avoided at all costs. Flavored coffees won't do you much good, either.
Use what's left once the pot has cooled down rather than the dregs at the bottom of your cup, and only do so if you're enjoying a regular brew without sugars or chemical additives. Otherwise, you may be in for some unpleasant surprises, like mold or infestations of unwanted pests.
Coffee, Pets, and Pests
Need one more reason to include coffee in your gardening routine? Coffee grounds can help to protect plants from destructive pests while attracting more of the critters that actually help to promote plant growth. Slugs and snails hate the flavor of coffee, and rabbits aren't big fans either. Meanwhile, earthworms, which are basically living fertilizer agents and gardening assistants who will happily work without pay, love the stuff.
Please be forewarned, though - consuming coffee grounds can be harmful and even fatal for some furry animals! If you have house pets, particularly those who like to explore the world with their curious tongues, be sure not to leave coffee grounds or coffee-soaked soil any place in your home or garden where they might be able to consume it.
If your pet does eat some soil laced with coffee, act fast and contact your vet or the nearest animal hospital right away; caffeine toxicity can cause serious damage to small animals.