Are Coffee Grounds Good or Bad For Roses?

Are you wondering if your spent coffee grounds could be useful in the garden? A hotly debated topic, sources vary on whether coffee grounds are good or bad for roses. In this article, rose enthusiast and gardening expert Danielle Sherwood examines the common advice that coffee grounds in the garden will give you bigger, better roses.

Spent coffee grounds being applied to the base of a rose bush.

Most of us count on the caffeine boost from a cup (or 3) of coffee to start our day. In fact, Americans alone drink an estimated 980 million cups a day! With all these coffee grounds laying around, wouldn’t it be great to repurpose them in your rosebeds?

Coffee grounds contain a combination of macro and micronutrients that have the potential to benefit your plants. But, don’t rush out and pour them on the soil just yet. It turns out that despite anecdotes to the contrary, this gardening “hack” is a bit more nuanced than many gardeners are aware of.

So- let’s take a closer look at the facts and myths surrounding the use of coffee grounds and their impact on your roses. Are they good, bad, or something in-between?


The Short Answer

The short answer is that spent coffee grounds can be beneficial to roses, when used the right way. They don’t replace balanced rose fertilizers. When used incorrectly, coffee grounds can have negative effects on the garden.

A Brief Overview

Close-up of unused coffee grounds pressed into rounded briquettes. Coffee grounds are dark brown, crumbly.
Coffee grounds are a popular kitchen scrap that is considered a great addition to your soil.

Why are spent grounds such a popular soil amendment? Well, if you’re like me, you’re all about a DIY approach to compost, and want to make use of excess kitchen waste.  Economical and easy-to-access, they are a tempting soil amendment.

Coffee grounds contain about 2% nitrogen, .06% phosphorus, and .06% potassium. They also contain small amounts of micronutrients like magnesium, iron, and calcium. Roses need these nutrients to grow, so it seems like they would be an excellent addition to your soil.

They are claimed to boost growth, repel pests, acidify the soil, and suppress fungal growth. Unfortunately, research doesn’t back up all of these superpowers. While they can benefit your garden, how much you use and your method of application matters.

Let’s look closer at the common statements made about using coffee grounds when growing roses, and what research tells us about their actual impact.

The Long Answer

Similar to using Epsom salt with your roses, a quick google search will give you conflicting advice if coffee grounds are safe to use with your roses. Some gardeners will say that it stunts the growth of your flowers, but others that they boost it.

Some say they’re good for worms, others say they harm them. Before your head starts to spin, here’s some sleuthing about what coffee grounds actually can and can’t do for your roses and the creatures that help them thrive.

Raising Soil Acidity

Beautiful blooming rose bush in a flower bed outdoors. The bush is young, small, has thin stems covered with complex pinnate leaves of oval dark green leaves with serrated edges. The flowers are medium size, classic rose shape, double, velvety red.
They do not contain enough nitrogen and therefore do not affect soil pH.

Roses prefer soil with a pH between 6-6.5, just slightly on the acidic side. Since coffee grounds contain nitrogen, many gardeners hope application will increase the acidity of their soil.

Unfortunately, spent they don’t contain enough nitrogen to impact soil pH. The nitrogen content of coffee is water soluble, so most of it is brewed into your cup, rather than left behind in the grounds. In fact, spent grounds have an average pH between 6.5-6.8, making them neutral.

To increase soil acidity, apply a product like elemental sulfur, which will interact with soil bacteria to transform into sulfuric acid, giving your plants a quicker boost. As with all soil amendments, this is only beneficial if your soil needs it, which can be discovered with a simple soil test.

As a Fertilizer Replacement

Close-up of a woman adding fresh compost to an overwintered rose bush in a spring garden. The bush has thick short trimmed green stems, covered with sharp thorns and young red shoots. The gardener is dressed in white gloves, blue trousers and a long-sleeved gray sweater.
Add coffee grounds to your compost to fertilize your roses.

We’ve already established that the pH of coffee grounds don’t raise soil acidity. But do the grounds provide other beneficial nutrients to our plants?

They can, but the amount and method matters. The truth is, we lack good studies on the effects of spent grounds on roses, and have to rely on anecdotal evidence and research conducted on other plants.

Studies based on broccoli, viola, sunflowers, leek, and radish revealed that the plants responded to coffee grounds with stunted growth, possibly due to caffeine content. 

Other studies indicate a negative impact to seed germination. High doses of nitrogen applied directly can burn roots. So, it’s reasonable to proceed with some caution before liberally applying.

Knowing that, how can you use them safely and effectively? If you want to use coffee grounds to increase the nutrient content of your soil, adding them to your compost where they can decompose and mix in with other organic matter is the best option. Evidence shows that keeping the amount around 20% of your compost is the ideal amount to provide an excellent source of nitrogen.

If you don’t compost, use spent grounds sparingly, and sprinkle on the soil around your roses. On top, place a mulch of wood chips, leaves, and other organic material that will help it break down.

Using as a Mulch

Top view, close-up of a gardener's hand in a black glove mulching the soil near a rose bush in the garden. There are small rakes in the hand. The bush has pale green stems covered with sharp thorns. Mulch is made up of bark.
It is not recommended to use spent grounds as mulch, as it repels moisture and reduces airflow.

Coffee grounds are composed of very fine particles that have a tendency to become compacted over time, forming a mat that repels moisture and reduces airflow.

You don’t want a hydrophobic barrier around your roses, so they are not a good choice to mulch your rose garden.

Instead, sprinkle no more than half an inch of coffee grounds into the soil and cover with a layer of organic compost or wood chips. This will help preserve moisture (roses are thirsty plants), and keep the ground from becoming compacted.

Coffee Grounds and Worms

Close-up of red california earthworms in coffee grounds in a paper bag on a wooden table. The worms have long, flattened, tubular pink-red bodies. Coffee grounds are dark brown, fine, moist.
Mix spent grounds with other leftover food to feed your compost worms.

Worms love organic matter, and spent grounds are organic matter, so feeding them via the leftovers from your morning joe is a win-win, right? It’s true that coffee grounds can provide nutrients for worms, but they must be mixed with adequate levels of carbon- containing materials.

In studies of 3 different composting methods, worm mortality increased significantly when adding spent grounds. However, this effect was mitigated by mixing in lots of carbon rich material, like cardboard. Be careful when using them in confined vermicomposting bins, where they have shown to kill and harm worms.

When applied directly to the soil, small amounts are unlikely to harm or attract worms. Once broken down and in interaction with other nutrients, coffee grounds can nourish them. They’re just not a prime attractant as some claim.

Using as a Natural Pesticide

Close-up of a female hand in a yellow glove spraying a pest spray from a white bottle on a rose bush, in a sunny garden. The rose bush has thick, strong stems with thorns and small young green oval leaves with serrated edges.
Coffee ground concentrate is not capable of killing pests.

This claim has been extrapolated from studies where foliar sprays with high concentrations of caffeine were applied. The caffeine content is actually much lower, and will not kill pests.

Does it discourage pests from taking over your roses? Maybe. You can find videos of slugs crawling right over coffee grounds to get to prized food sources, but also videos of them avoiding coffee ground barriers.

While anecdotes abound, there is zero scientific evidence they repel rose pests like aphids, spider mites, and Japanese beetles. The jury is still out on this one! Give it a try this spring and let me know how it goes.

Fungal Disease Supression

Fungal disease of rose powdery mildew. Close-up of an infected rose bush with white bloom on leaves and stems. Some leaves are dry and curled.
Spent grounds have antibacterial properties that can kill soil microbes.

Here we have another resounding maybe. There is some evidence that coffee grounds have antimicrobial and antibacterial properties that might prevent fusarium wilt and Pseudomonas on tomatoes, spinach and beans.

However, soil microbes are a good thing, and we don’t want to kill off anything beneficial in our garden. We need further study on the impact of spent grounds on common fungal diseases in roses. If you like to roll the dice, conduct your own research and give it a try!

Final Thoughts

Spent coffee grounds (never fresh- they contain too much caffeine) can be a great addition to your compost bin. You can also scatter a light layer around your roses, and mulch over it with compost, wood chips, or pine straw. These are safe ways to use up all those extra grounds!

However, they are not a miracle worker in the garden, and can even be detrimental when used too liberally. Let’s hope more research on coffee grounds and roses is conducted soon, so we know we’re really helping, rather than inhibiting our plants.  As with all gardening hacks, use caution, and remember that nothing replaces a good balanced fertilizer. Good luck with your roses!

Bright pink rose growing in garden with light pink petals and streaks


15 Tips For Growing Beautiful Roses This Season

Getting started growing roses can be intimidating. Luckily, their fussy reputation is exaggerated! Armed with knowledge of their basic needs, any gardener can grow beautiful roses. In this article, gardening expert and rose enthusiast Danielle Sherwood shares 15 of her top tips for gorgeous blooming roses!

rose growth stages


Rose Growth Stages: How Fast Do Roses Grow?

Are you wondering how long it will take your rose seedling or bare-root plant to grow into a large, blooming bush? Roses grow quite quickly, but there is a lot of variability depending on variety and age at transplanting. In this article, gardening expert and rose enthusiast Danielle Sherwood walks you through the stages of a rose’s growth cycle.

Bare root roses at garden center wrapped in green plastic at the base of the rose canes.


Are Bare Root Roses Worth Buying & Planting?

Have you been tempted by the plastic-wrapped bare-root roses at your local big box store? You may be wondering if they’re as great of a bargain as they seem. In this article, rose enthusiast and gardening expert Danielle Sherwood looks at the pros and cons of buying what are known as “body bag roses” to help you decide if they’re a bargain or a bust!

miniature rose varieties


17 Miniature Rose Varieties for Compact Garden Spaces

Are you looking to make the most of a small garden or patio space? Miniature roses, with lots of colorful blooms on a compact plant, might be the solution for you. Often mistakenly discarded as annuals, miniature roses are just as hardy and long-lived as their full-size counterparts. In this article, expert gardener and rose enthusiast Danielle Sherwood shares her top miniature roses for small garden spaces.

heat tolerant roses


17 Heat Tolerant Roses That Thrive in Warm Climates

Do you need a rose that can stand up to the heat? Gardeners in hot climates know that growing roses when temperatures soar can be a challenge. Fortunately, there are some rose varieties that tolerate heat better than others. In this article, gardening expert and rose enthusiast Danielle Sherwood shares a list of roses known for looking good despite hot summer temps.

eggshells roses


Are Eggshells Good or Bad For Roses?

We all love the idea of DIY organic fertilizers, but do eggshells really work wonders in the garden? Or is this just another gardening myth you can ignore? In this article, rose enthusiast and gardening expert Danielle Sherwood examines the common advice that using eggshells results in better roses.