One of the recurring questions that coffee lovers often ask is: what to do with the spent coffee grounds?
We’ve talked before about why it’s a bad idea to put coffee grounds down the drain, but it can feel like such a waste to just throw them in the trash. One solution: garden with them. For some gardens, coffee grounds are a great addition.
But are there some plants that like coffee grounds more than others? We have the answer!
Used Coffee Grounds Are Nitrogen Rich
One of the primary nutrients that plants need to grow strong is nitrogen.
In most settings, plants get their minerals through the breakdown of organic material in the soil; this is one reason that a lot of ecologists suggest using dead leaves from fall as garden mulch.
Coffee is very rich in nitrogen, which makes up about 2% of ground coffee by volume. And most of the acid content in used coffee grounds is actually in the coffee you brew.
As a result, they are close to neutral pH, making them a good compost material or soil enrichment for your garden plants of all varieties.
Did you know that plants react to caffeine?
Research suggests that the perk-you-up chemical does the same thing for plants in small doses.
Low doses of caffeine stimulate the usual biological processes in plants, including water absorption and photosynthesis. For example, this study using sunflowers found that small doses of caffeine led to faster plant growth.
However, too much stimulation is bad for plants just like it can be bad for humans; the same study, and a few others, found that higher doses tend to stunt the growth and the seed yields of the hardy sunflower, along with broccoli and leek plants.
It’s definitely important not to use a heavy hand with your coffee grounds–or stick with decaf coffee grounds for your garden.
Another way to get around the issue is to use the coffee grounds as a compost material.
Earthworms love coffee grounds and will help break down your compost much more quickly if you include some spent coffee grounds in your compost bin. Coffee grounds also retain water, which is a big help.
Why Garden With Coffee Grounds?
As mentioned before, nitrogen is a vital mineral for plant growth and development.
It’s one of the major components of fertilizer, and it helps stimulate plants to put out lots of leaves, and it’s essential for the development of strong stems.
Coffee grounds are rich in this key mineral, and being close to pH neutral, they make a great enrichment for your dirt.
Coffee Is Abrasive
But there are other reasons for using coffee grounds in your gardening. Ground coffee is abrasive; it actually makes a fairly effective exfoliant for that reason.
This same property may help to repel slugs from your plants. Since the slugs have to slither through and over the dirt to get to each planting, a layer of coffee grounds on top of the soil is far from pleasant for them.
Used grounds may also help keep insects (other than worms that live in the soil) away from your plants, at least those that have to crawl to get to them.
Caffeine is a stimulant, but most biologists believe it evolved originally as a kind of natural pest repellent: the same chemical that peps us up can cause very big problems for many insects.
Coffee Helps Keep Weeds At Bay
Coffee grounds also seem to inhibit weed growth.
Scientists aren’t entirely sure why this is the case, but using coffee grounds as fertilizer may help to suppress weeds. And it also may deter cats from deciding that your lovely garden makes for an ideal litter box.
As with the insects and other garden pests, cats seem to avoid coffee since it’s mildly poisonous to them.
What Plants Like Coffee Grounds?
A lot of plants love coffee grounds!
Plants that tend to be acid-loving are also coffee lovers, even though used grounds tend to be only slightly acidic.
If you don’t have any acid-loving plants, you can still use your coffee grounds in the soil or in a compost bin, the friend to all gardeners.
Plant types that like coffee grounds in the soil include:
Wrapping Up: Coffee For The Garden
Using coffee grounds in your gardening efforts makes good sense: you can ensure that the coffee ground leftovers don’t go to waste while also giving your plant a pH-balanced source for nutrients they need to grow strong.
So what plants like coffee grounds? All acid needing plants like coffee, as long as you’re careful with the caffeine dosage.
Roses are especially fond of them, but the leftover coffee beans make a good soil addition for almost any plant you might give them to, as long as you’re careful.