Do Burning Coffee Grounds Repel Flies? A Greek Island Trick to Try Outdoors
- Astrid van Essen
- 10 minutes ago
- 7 min read
On a hot afternoon on the Greek island of Skopelos, I noticed something slightly odd appearing on the tables of a taverna: a small cup wrapped with aluminium foil, filled with dry coffee and quietly smoking. It was not there for atmosphere. It was there for the flies.
The set-up was wonderfully simple. The cup had pebbles in the bottom to give it weight, with foil forming a shallow dish over the top. Dry coffee sat on the foil and was allowed to smoulder rather than burn with a flame. At another table I spotted an even simpler version using an ashtray lined with foil.
It is exactly the sort of low-tech Mediterranean trick that makes you wonder whether it is worth trying at home. So, do burning coffee grounds really repel flies, and can you use rosemary or lavender in the same way?
The Greek taverna trick I spotted on Skopelos
When food arrives outdoors in summer, flies often arrive with it. Instead of sprays or plug-in repellents, this taverna used a tiny source of aromatic smoke close to the table. The coffee was not blazing. It was gently smouldering, creating a steady ribbon of smoke around the eating area.
What interested me most was how improvised the holder was. One version used a cup weighted with pebbles so it could not easily tip over in the breeze. The top was covered with aluminium foil to hold the coffee. Another used a heavy ashtray with foil inside. Both did the same basic job: keep a small amount of smouldering material stable and away from the table surface.
Do burning coffee grounds repel flies?
There is plenty of anecdotal support for this trick, particularly around outdoor dining, but there is not strong scientific evidence showing that burning coffee grounds are a reliable fly repellent in the same way as a tested insect-repellent product.
The most likely explanation is simpler. Flies rely heavily on scent when locating food, and many flying insects avoid areas with persistent smoke. Smouldering coffee creates both smoke and a strong roasted aroma, which may make the immediate area around a table less appealing.
That means it is best treated as a practical outdoor experiment rather than a guaranteed solution. If you are sitting outside and the flies are becoming annoying, it is inexpensive, easy to try and does not involve spraying anything around your food.
How to burn coffee grounds outdoors
The important word here is smoulder. You want a little smoke, not an open flame. The coffee also needs to be completely dry. Damp coffee grounds are difficult to light and tend to go out quickly.
Method 1: the weighted cup and pebble method
Choose a sturdy ceramic cup, metal cup or other small heat-tolerant holder that you do not mind using for this purpose.
Add a layer of small pebbles or gravel to the bottom. This gives the container weight and helps stop it tipping in a breeze.
Lay a piece of aluminium foil across the top and press it down slightly to create a shallow bowl.
Add one or two tablespoons of completely dry coffee grounds or ground coffee.
Light a small edge of the coffee. Once it catches, gently blow out any flame so the coffee continues to smoulder and produce a thin stream of smoke.
Place the holder on a stable, heat-resistant outdoor surface, away from anything flammable.
Method 2: the ashtray or heatproof dish method
This is the simplest version. Line a heavy ashtray or small heatproof dish with aluminium foil, add a shallow mound of dry coffee and light one edge. Blow out the flame and let the coffee smoulder. A heavy container is useful outdoors because it is much harder to knock over than a lightweight saucer.
Why put pebbles in the cup?
The pebbles are not part of the insect-repelling effect. Their main job is stability. A cup containing only a little coffee at the top could easily be knocked over by a hand, a gust of wind or a busy table. The stones lower the centre of gravity and make the whole set-up feel much more secure.
They may also create a little more distance between the hot foil and the base of the cup, but I would still treat the entire holder as hot and keep it on a heat-resistant surface.
Used coffee grounds or fresh ground coffee?
Both can be tried, but used coffee grounds must be dried thoroughly first. Spread them in a thin layer on a tray or plate and leave them until there is no noticeable moisture left. If they are still damp, they are far more likely to steam or go out than to smoulder.
Fresh ground coffee is naturally drier and may be easier to light, although using yesterday's coffee grounds is obviously the more economical option. Whichever you use, start with a small amount. You do not need a large pile to create smoke.
Can you use rosemary or lavender instead of coffee?
Yes, you can experiment with completely dried aromatic herbs, but I would describe these as variations on the method rather than proven substitutes for coffee. Research into insect-repelling properties often looks at essential oils or concentrated extracts. That does not automatically mean a handful of smouldering herbs will produce the same effect.
Rosemary
Dry rosemary is probably the most natural alternative to try because the woody stems and needle-like leaves can smoulder well when thoroughly dried. Use a small pinch rather than a tightly packed bundle. If you grow your own, you can also read How to Grow Rosemary for Incense: Planting & Harvesting Guide for ideas on harvesting and drying it for aromatic smoke.
Lavender
Dried lavender can also be used, especially the stems and loose dried flower heads. It produces a softer floral aroma, although it can burn quickly if you use only delicate flowers. Mixing the flowers with some dry stems helps slow things down. See How to Grow Lavender for Incense: Planting & Harvesting Guide if you want to grow and dry your own supply.
Rosemary and lavender together
For a Mediterranean variation, combine a small amount of dried rosemary with a little lavender. Keep the mixture loose so air can reach it. The aim is still a slow smoulder rather than a hot flame. This version is especially pleasant for an outdoor evening table when you want something more aromatic than coffee.
Can you mix coffee with herbs?
You can. A base of dry coffee with a pinch of rosemary or lavender on top is an easy way to experiment. Coffee tends to provide a steady smoulder while the herbs add their own scent. Start with very small quantities because dried herbs can catch more quickly than coffee grounds.
I would not add essential oils to the burning mixture. Concentrated oils can behave unpredictably around heat and are unnecessary here. Stick to plain dried plant material.
Where should you place it on an outdoor table?
Place the holder near the edge of the seating area rather than directly beside a plate or underneath someone's face. If there is a light breeze, position it so the smoke drifts across the area where the flies are gathering without blowing directly at diners.
For a long table, two very small holders at opposite ends may work better than one large smoky container in the middle. The point is to create a light aromatic haze, not to turn dinner into a bonfire.
Safety first
Use this method outdoors only, in a well-ventilated area.
Use a heavy, heat-resistant holder on a stable, heat-resistant surface.
Keep it well away from dry grass, paper napkins, table decorations and other flammable materials.
Never add alcohol, lighter fluid, cooking oil or any other accelerant.
Keep children and pets away from the hot container and smoke, particularly birds, which are very sensitive to airborne irritants.
Do not leave smouldering coffee or herbs unattended.
Extinguish everything completely with water before disposing of the remains.
Is this basically a form of incense?
In a practical sense, there is some overlap. Incense works by allowing aromatic botanical material to burn or smoulder slowly enough to release scented smoke. Here, the intention is different. You are not using the smoke for fragrance, ritual or atmosphere. You are creating a small smoky zone around an outdoor table in the hope that flies find it less inviting.
If you are interested in the wider world of botanical smoke, you might also enjoy What to Do After Smoke Cleansing: 7 Simple Steps and What Is an Incense Trail? How to Make and Burn One. They explore how plant materials are used for aromatic smoke in a very different context.
A simple Greek island trick worth trying
What I liked about the Skopelos version was how ordinary it was. No specialist burner, no expensive product and no elaborate ingredients. Just a weighted cup or ashtray, a piece of foil and something dry enough to smoulder.
Will it solve every fly problem? Probably not. But for a summer lunch or evening meal outside, it is a clever little trick that is easy to test. And if coffee is not your thing, a pinch of rosemary or lavender gives the same idea a distinctly Botanical Blueprint twist.
Frequently asked questions Do Burning Coffee Grounds Repel Flies
1. Do burning coffee grounds really keep flies away?
They may help discourage flies around a small outdoor area, mainly because of the smoke and strong aroma, but the evidence is mostly anecdotal. Treat it as an outdoor trick to try rather than a guaranteed fly-control method.
2. Can I burn used coffee grounds?
Yes, but they must be completely dry first. Spread used grounds out in a thin layer and allow all moisture to evaporate before trying to light them. Damp grounds usually struggle to smoulder.
3. Can I burn rosemary to repel flies?
You can try smouldering a small amount of fully dried rosemary outdoors. Rosemary has a strong aromatic profile, but research on rosemary essential oil should not be taken as proof that burning the dried herb will reliably repel flies.
4. Does burning lavender keep flies away?
Dried lavender can be used as an aromatic variation, especially mixed with a little rosemary or dry coffee. It may make the immediate area less attractive to insects, but it should not be presented as a proven replacement for an insect repellent.
5. Is it safe to burn coffee grounds around pets?
Keep pets away from both the hot container and the smoke. Use the method outdoors with plenty of ventilation, never allow animals to investigate the holder, and avoid using smoke close to birds or any pet that is sensitive to airborne irritants.
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