Many gardeners swear that coffee grounds work miracles for plants, including roses. And adding some to your flowering shrubs and climbers can have a positive effect, as they are rich in nutrients like nitrogen and calcium.
But you cannot use them randomly; rose plants are delicate, and you need to know how to feed them.
Leftover coffee grounds can be very beneficial to roses when used in moderation. They feed the plants with readily available nutrients (nitrogen, phosphorus and potassium, etc.), lower soil pH, attract worms and improve soil structure. Also a natural repellent, coffee grounds are very useful in the fight against garden pests such as aphids, slugs, snails, and ants that are harmful to the roses.
While there are benefits to adding coffee grounds to your rose garden, there are a few downsides you need to be aware of… Use coffee grounds sparingly, or they can burn the roots of your roses due to the particularly high nitrogen content.
These are the basic rules, and now we can talk about all the details you need to make the best use of coffee grounds to help your roses give wonderful blooms.
Fresh and Used Coffee Grounds for Roses– a Matter of pH
Fresh and used coffee grounds have very different properties, especially when it comes to the pH, the level of acidity and alkalinity. You need to keep this clearly in mind if you love your roses.
Fresh coffee grounds are very acidic, with pH under 5. Roses cannot stand very acidic soil, and if you feed your plants with unused coffee grounds, you risk lowering pH far too much.
Plants need a pH they like because otherwise they cannot absorb nutrients in the right quantities. A rose growing in acidic soil under 5.5 will have problems growing. Leaves may yellow and blooms will be scarce and often sick.
Used coffee grounds lose the acidity and they have an almost neutral pH, between 6.5 and 6.8 (7.0 is perfectly neutral).
This acidity is fine for roses, who can tolerate soil pH between 5.5 and 7.5 but ideally the want it between 6.0 and 6.5. And if you have been growing roses, you will know that they are delicate and demanding.
So, it is safe to feed roses with used coffee grounds, but nit with fresh ones.
But this does not mean that you cannot categorically use fresh coffee grounds with roses…
Can You Feed Fresh Coffee Grounds to Roses?
Rules have exception, and feeding fresh coffee grounds to roses is possible too. In the introduction I gave you a simple, safe and general rule. If you are not an expert gardener, I would in any case advise against using unused grounds with roses.
However, if the soil is very alkaline, you may correct it with fresh coffee grounds. By very alkaline we mean considerably above what rose can stand, so well above 7.5.
However, if you feel that you need to correct the soil acidity for your roses, never scatter fresh coffee grounds near the rose itself. Keep a safe distance and allow the grounds to seep into the soil slowly. If you put them near the plant itself, they may end up burning your roses!
And again, proceed by stages and avoid large quantities of fresh coffee grounds. This is the only case when you may use fresh coffee grounds for roses – do it only if the alkalinity of the soil is actually damaging your plant, and if you are quite experienced as a gardener.
Now, what do used coffee grounds give to roses?
Benefits of Coffee Grounds for Roses
Coffee grounds contain many nutrients that plants need, including roses, such as:
In particular, coffee grounds are an excellent source of nitrogen, which is the nutrient that most plants need most, including roses.
What is more, the nutrients in coffee grounds are readily available for roses to absorb. This means that you can give your roses a quick boost of energy using coffee grounds.
With organic matter, like compost, the nutrients are released slowly and the need to be broken down by microorganisms before your rose can actually use them.
Therefore, if your rose is showing signs of nutrient deficiency, feeding it fresh coffee grounds can be a good solution.
But there are more benefits of coffee grounds for roses, let me tell you…
Utilize Coffee Grounds for Roses to Reduce Soil Contaminants
Sometimes there are contaminants in soil that can harm your roses, and coffee grounds can help. These are usually heavy metals which the plant absorbs together with the nutrients and which can cause serious damage, for example:
If you live near a polluting site, like an incinerator, a refinery, or in a heavily trafficked area, used and charred coffee grounds absorb heavy metals. This way, they will not be available to your thorny bush or climber to absorb. And do remember that roses are quite sensitive to pollution!
And you will be pleased to know that coffee grounds have even more beneficial effects! Still two to go!
Coffee Grounds Improves Soil Structure and Nurtures Soil Ecology
Coffee grounds are excellent to improve the health of your soil! And your roses will thank you for it. “How does this happen,” you may ask? Simple, coffee grounds attract earth worms!
You may known that earth worms have amazing effects on your soil, like:
If your soil is showing signs of infertility, if it is looking sterile, or even if you have heavy clay soil, or if you have just bought your property and the soil has been neglected for some time… then coffee grounds can be an excellent way to improve it!
Use Coffee Grounds as Mulch to Improve Drainage
Put simply, coffee grounds improve the drainage qualities of your soil, and roses love very well drained soil. They are actually excellent for this, because they are very fine and they can even break down clay, which sticks together quite tightly, and which is made up of very thin parts.
They act a bit like sand; the grain stays compact and it breaks up lumps of soil that stick together.
Thinking about clay, which is a drainage nightmare for gardeners, gravel and similar solutions only have a very limited effect. Instead coarse and fine sand and coffee grounds are just perfect for the job!
You see, there are many advantages to coffee grounds for roses, as well as for other plants – not just the nutrients!
But the question is, “How can we use coffee grounds for roses safely and efficiently?” We are going to see it right now, there are a few ways, in fact.
How Much Coffee Grounds for Roses?
We said that you need to feed coffee grounds to roses in moderation. But how much is too much? Now you know that excessive nitrogen and other nutrients is dangerous for plants, and you know that coffee grounds release them promptly, you need to be careful, so…
Use about a pound of coffee grounds for each mature rose plant (450 grams). This is the dosage for a whole year.
This is a safe dosage you can rely on, but this does not mean you can feed them whenever you want… Let’s talk about it!
When and How Often Should You Feed Coffee Grounds To Your Roses?
Timing is of the essence when feeding coffee grounds to roses. There are a few rules you need to follow to be safe, and they are…
For a repeat bloomer, give them half the dosage early in spring and divide the other half for each expected further bloom.
For a late bloomer, give your rose half the dosage in early spring and half about 2 weeks before the expected bloom.
And now we have seen how much and when to feed your plants, let’s see how, because there are different methods you can use…
How to Use Coffee Grounds for Roses
There are few easy ways your roses way to feed your roses with coffee grounds, so they can can safely enjoy a good shot of joe.
Scatter Them Around Rose Bush
The simplest way to use coffee grounds to help your roses is to scatter them gently over the soil next to the rose plant. But avoid full contact with the plant itself. This method has a few advantages and some disadvantages though.
On the other hand…
And remember that roses don’t just suffer from nutrient deficiency; they can also suffer from nutrient toxicity, which is when they have too much of one or more of the minerals.
Coffee grounds are particularly rich in nitrogen, and too much of it can cause serious problems, like:
Mix Them with Sand
Sand and coffee grounds are excellent for drainage, which roses need. Mixing them will:
Always keeping the dosage in mind:
No need to dig the sand and coffee grounds mix into the soil! Actually avoid disturbing the soil at any cost! Tilling impoverishes the soil enormously, it sets back the hard work of small and micro organisms, and finally, you may even damage the surface roots of your plant!
Don’t worry the rain and worms will slowly take the mix into the soil, and this will also give a slower and safer release of nutrients.
The quantity of sand depends on how much you wish to improve your soil’s drainage.
Water Rose Plants With Leftover Coffee?
You can feed your roses with coffee grounds when you water them. This is a simple solution with some advantages:
For this reason, this system is only suitable for small quantities. Why? Let’s see how you do it, and it will become clear.
These are the main methods to feed your roses with coffee grounds, but I want to give you my advice.
Add Coffee Grounds To Your Compost Pile
Adding coffee grounds to compost is not technically feeding them to your roses but it’s related. The fact is that they get decomposed in the process of making compost. But they are very useful, and in compost they are good for roses as well as all other plants.
In fact they greatly help the quality of your compost. But you need to know one thing; in compost “coffee grounds are green”. What do we mean by this? We mean that compost has two main nutrient ingredients:
nitrogen and carbon. Because nitrogen rich matter is green, and carbon rich matter is brown, gardeners call these two “green” and “brown” respectively.
So, leaves are rich in nitrogen, but wood shavings are rich in carbon for example. But the color of coffee grounds is misleading: it is brown, but it is very rich in nitrogen, so use them to add to the nitrogen portion of your compost heap. Make sure you mix them in well, and scatter them in layers, rather than putting a big quantity all in one place.
One note: you can also use fresh coffee grounds in your compost heap.
Ok, but how about if you have many rose bushes? Where can you get all those coffee grounds?
My Favorite Method
It is mixing them with sand! Why? It has the most advantages and no real disadvantage. Some gardeners suggest mixing them with water but I actually find it messy with all the grounds that stay in the tank, and the distribution is far better with sand.
“But if I want fast nutrient release?” Well, simply water them afterwards! And we have almost come to the end, but there is still a little trick I want to show you…
Where to Get Coffee Grounds
For a single rose plant or just a few, the coffee grounds you use at home may suffice. Of course it depends on how many coffees you drink! If you need some more, you can always ask friends and neighbors: I am sure they will be willing to help you with your gardening.
But if you need a lot, you can try asking businesses that have no use for them, for example:
They will give them to you for free, so don’t worry about the cost. It’s free food for your beautiful roses!
Give Your Roses and a Cup of Coffee!
We can’t say that roses drink coffee like we do, but we could say that they like them and they can feed on them. Just follow the guidelines in this article and you will use them safely and at the right times.
So, next time you have a cup of coffee, think about feeding your roses too!
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.