Having some potted herbs around your house is a great idea to harvest fresh and delicious leaves for your dishes. However, do you know that some herbs might also help in keeping away unwanted insects/pests from your kitchen? This is a 100% natural alternative (there is nothing more natural than a basil plant) that can be a valid replacement of commercially available insecticide.
Which indoor herbs repel unwanted insects? Herbs famous for their insects-repelling capabilities are:
- Bay leaf
- Sweet woodruff
- Lemon balm
As you can notice, you have a plethora of allies to prevent unwanted visitor to roam in your kitchen. However, is it sufficient to have one of these herbs in your kitchen table to protect the whole house? Which herbs might help you against ants, and which one against wasps? To know more, keep reading.
Does One Herb Repell One Insect? More Than That
Each herb produces a specific scent and oils that evolved to be more effective against a particular category of insects (the ones the herb was exposed the most) than others. Some of them even purify the air. However, the good news is that many herbs repel way more than insect type. Based on the experiences of several gardeners and university studies (such as the American College of Healthcare Sciences and Mississippi State University), the table below summarises which insect common herbs are able to repel:
Hence, as you can see, each herb has a different power against one or more insects. If you want to start growing herbs also to repel insects, hence the best candidates are:
These herbs indeed can repel the majority of common insects (ants, aphids, flies, and mosquitoes) that might access your home.
However, if you do not want so many different herbs (with their different needs, primarily in terms of watering), I do recommend going with mint. Indeed, among the above, is the easiest one to maintain and grow.
When I say that a potted herb is easy to maintain, I mean that it allows you some “mistakes” such as over or underwatering without being damaged too quickly. Moreover, mint is an edible herb, a great addition to countless recipes such as the portegues-style mint rice (one of my favorite using mint).
The only warning I have is to use a single container with a large surface for each single mint herb. Indeed, mint is quite invasive and might overtake (subtracting nutrients) any other herb/plant unlucky to be in the same container. Moreover, if placed close on the windowsill, it might extend its stem significantly subtracting lights to other surrounding herbs (as happened to me).
However, I did not discuss yet how these herbs repel insects. Is it sufficient just to have a few potted herbs here and there? Or perhaps you need to do something more to leverage their real repellent power?
How Should You Use Insect-Repellent Herbs?
As discussed in an authoritative academic study from the NH institute, here, the name “insect-repellent” is misleading. Indeed, those herbs do not produce any substance that actively put off insects. These herbs insects produce volatile substances (odor for us) that inhibit the insect smell. Hence, the delicious (for people) scent produced by a mint herb halts the sense of smell of mosquitos.
This will prevent the mosquito from biting you as it does not know where to bite in the first place. Indeed, its sense of smell drives it to its prey. The same applies to all other “repelled” insects.
This information is crucial for you! Indeed, you know now that if you want some effect, the odor produced by your herbs should reach the insect before entering your apartment. Indeed, once inside, an insect will not escape due to the herb (it does not repel them). It will just end up roaming around.
Tip 1: The best place to keep these repelling herbs is definitely close to the potential access that insects have to your house. So close the main entrance door and on windowsills are the best spots.
Tip 2: Some also suggest to rub the herb leaves on your skin or clothes. This will have a more powerful effect than merely having a plant sit on a pot. Indeed, by damaging the leaves, you are releasing those smelly oils that will end up covering your clothes. So, you will be free to walk around with this “aura” or protection from annoying insects. This is particularly useful against mosquitoes during hot summer days.
However, I do not recommend to rub such leaves on your skin directly, as a few gardeners suggested, as it might trigger some allergic reactions. A downside of this approach is also the short duration. Indeed, the oils are extremely volatile (it means they will evaporate very quickly), making the scent disappear in a few hours at most.
However, there is another more effective approach to use herbs’ oils. An approach totally natural that provides way better results (and can entertain you with a bit of Do It Yourself stuff). I am talking about an organic insecticide that you can produce by extracting the natural oils of your herbs. Let’ see how!
Make An Organic Insecticide With Your Herbs
An organic insecticide is way more effective and practical than rubbing the leaves on your clothes. Indeed, herb oils, through the appropriate process, can be transferred in a liquid solution that you can spray on yourself, your kids, or in the room that you want to protect. This can be done more effectively compared to rubbing a few leaves.
You can prepare an effective organic insecticide with just a few ingredients you might typically already have at home. For this recipe you need:
- 4 cups of mint leaves: as I said before is one of the most effective insect-repellent herbs;
- 8 garlic cloves: garlic, although not mentioned in the previous list (as it is not a herb), it is well-known to deter a large variety of insects (especially flying ones such as mosquitos and flies) and small animals. This is because of the sulfur-based compound it contains (for more, this interesting academic reading). You can also replace it with garlic powder with similar results accordingly to other gardeners.
- 3 cups of distilled water: this is an “inert” medium where the mint oil and active garlic ingredient are released. You can also use less water, resulting in a higher concentration of insecticide (although in lower quantity).
The steps are straightforward to follow. You need to:
- Blend the mint leaves in a blender;
- Place the so obtained mixture in a pot with distilled water;
- Place under heat. Once it starts boiling, you should take it out from the heat and let it sit. After a half-hour or so (the solution is warm) add the garlic heads and let it sit for 5-10 hours.
Boiling the mint leaves allows transferring its oil to the water solution. However, the same does not apply to garlic (that you should not boil). Indeed, the active components in garlic are neutralized by high temperatures.
That’s why I prefer adding garlic at the end, allowing its chemical to be gently released into the water without altering them. Tip: I usually do prepare at night time so to be ready the morning after.
- Filter the solution to remove the trace of garlic and mint pieces;
- Place the solution on a vaporizer, and spray on the area, or herbs where the insects you want to get rid off typically hang around. Even if you do not see them, you can still notice the damages that might cause (like holes in the leaf).
Given that the solution will slightly smell of garlic (not much though due to the boiling process), you might want to avoid to spray it on your clothes. I would prevent contact skin, although it should not pose any risk (if you are not allergic to mint or garlic).
This type of solution is ideal to be placed on herbs or any plant. This will help get rid of nasty insects that might be lurking in the surroundings (in case you noticed holes in your leaves as discussed in this article). In such a case, you might need to apply the spray for 3 weeks (once a week), and your herb should be recovered within that time frame.
Talking with a few gardeners, I found many variants around this recipe, and you are free to experiment with them. The main idea is to let the insect-repellent chemicals in your herbs to be released in an inert medium that you can spray where needed.
For instance, many added (or replaced) mint with peppermint with great results against ants. Others, add soap to the solution (ideal if you spray plants) to increase its ability to fight aphids. Also, vinegar, a natural substance powerful against aphids and ants, is often added to the solution. Among species, cayenne pepper is definitely the most used to create an effective organic pesticide.
Do Indoor Herbs Attract Insects?
You might wonder if indoor herbs can be a source of insects. Indeed, it is true that they repel the bad guys, but at the same time are still herbs, so you might expect to attract (other) insects in general.
This is not the case. I currently have 10+ pots (in my darker and darker flat in the UK) with basil and mint and no trace of insect whatsoever so far.
If someone might experience problems with insects, this might be due to one of the following:
- Soil with “surprise”: Did you buy (here an excellent potting soil), made yourself (for more details, this article)? Or perhaps you decided to use some garden soil that, more often than not, comes with insects and pests with it. If this is the case (and you did not sterilize it), such soil might be the incubator of nasty visitors. Do not forget that also low-quality potting soil, or soil exposed to ill plants (again, if not sterilized), can carry potentially harmful insects.
- A grown herb “with hidden visitors”: perhaps, for a faster harvest, you decided to go for an already grown herb (bought at the supermarket as I explained in this article). There is nothing wrong with that. I do it all the time. However, before bringing your herb indoor, you need to check for the presence of tiny hosts.
Indeed, spider mites and aphids are extremely small and so easy to pass unnoticed with a superficial check. Hence, before buying, just look beneath the leaves. If you notice spots, just avoid buying the plant. Indeed, this can be egg laid by spider mites or the spider mites themselves (if you look closely though you should be able to see them).
- Get from the outside: another case in which you can find insects on your herbs is because they found fortunate ways they get access from the outside. As detailed in this article, aphids, for instance, can even use your pet fur as a way of free transportation. Once on your herb, if untreated, it will not be long after you also see ants.
Indeed, the sweet substance that aphids “produce” (as a waste, known as honeydew) is a nutrient-rich and delicious meal for ants that will start even farming and protecting aphids! This is the worst case for your herbs, and you might want to use the recipes discussed above to produce an organic insecticide. In this case, I will also add soap (just a teaspoon) to increase its efficacy.
Herbs Can Also Repel Small Animals?
Among animals that might have paid a visit to your house, especially if you live in the countryside, there are mice and chipmunks.h
A mouse might access your house during winter, attracted by the warm and smell of delicious food you might prepare. In this case, you need to know that your herbs can also be used to repel mice. Such herbs are sage, rosemary, peppermint, lavender, and oregano.
As stated before, you can create a solution with boiled leaves adding, if you want to increase the potency, garlic (yes, it also repel rats!). Another option is to take some leaves and place them in an open sachet placed where you do not want the mouse to go.
For instance, at the kitchen entrance or in drawers and closets. However, bear in mind that the leaves will lose their effect after a few days as they will dry out. The efficacy of such technique in deterring mice and rats has been demonstrated by rigorous academic studies.
When the rats were exposed to i.e. wintergreen oil+chilli, wintergreen oil+peppermint oil, bergamot oil, wintergreen oil+peppermint oil+bergamot oil or bergamot oil+geranium oil, we found that the numbers of visits to the testing core and the time spent in the inner zone were lower […] indicating that the rats were most likely trying to avoid the closed contact to these substances.Source: Chulalongkorn University
In case a chipmunk decides to take residence in your home (very likely in the empty spaces in your wall or beneath the floor), the best allay is peppermint. Differently from what I said for insects previously, peppermint is a true repellent for this animal as it triggers a respiratory irritation in these animals.
You can place peppermint leaves in the feeding/storing food area (chipmunks have the tendency to accumulate food in specific spots). Also, you should look for wall areas and floor that may serve as an access point, or even worse, a nesting. However, the scent of peppermint tends to fade after a few days. Hence, it is better to rely on a DIY repellent (as the one discussed before, but using peppermint) for longer and better results.
Nevertheless, I have to be honest about the matter. The above remedies, given the significantly larger size of mice and chipmunks, compared to insects, lead to a lower degree of success. Indeed, if a mouse finds warmth and food in your house, herbs will keep him away, but very likely it will not be enough to leave your place.
A more practical solution, always based entirely or almost, on herbs, is to use a pesticide that you can find in the market! Why? Keep reading to know more.
DIY Or Buy an Insecticide?
Now you know how to produce an organic insecticide just using your herbs and a handful of natural ingredients you probably already have in your kitchen. So, why not everyone does produce its own insecticide and still rely on the “market” version? Well, let’s analyze the factors that might drive your decision to opt for homemade options or market ones. For this purpose, I used:
- Time: how long does it take to have “access” (or effort) to the insecticide or;
- Costs: the higher the cost, the less incentive to buy it;
- Effectiveness: more effective is in removing the pests, the better;
- Rapidity: the longer it takes to have effects, the less appealing for you might be;
- Safety: I am referring to the possibility of eating your herbs after treating them with insecticide. Of course, growing edible to not be able to eat them nullify the whole purpose of growing edible herbs;
- Environmental friendly: this is something that you might look at if you want to reduce your impact and carbon footprint
|Factor||DIY Organic Insecticide||Bought Insecticide|
|Time||10 hours (although only half an hour to prepare it)||Just a click on Amazon (instant)|
|Cost||Almost zero||Around $10 for a litre|
|Against||1 or a few insects||Up to 100 different insects and small rodents|
|Safety||Safe||Depends on the application|
|Environmental friendly||Yes||Generally no (chemical process + plastic packaging)|
Hence, as you can see from the above table, there is not a clear winner in all categories. Therefore, what you should go for really depends on your purpose and ideals.
For instance, if you have an herb that you want to save at all costs as in an advanced state of pests infestation, I would not go for a DIY insecticide. Indeed, such an option might take 1-2 weeks to start producing some noticeable effects. At that time, your herbs might be already gone. On the other hand, a commercially available insecticide acts way quicker. This is due to 2 different reasons depending on the type of insecticide:
- Organic: these kinds of commercially available insecticides, are just a DIY version on “steroids”. This means that they still based entirely on natural ingredients (herbs oils and inerts medium) as in your DIY.
However, the concentration is way higher, something that would be challenging for you to achieve due to the number of leaves required. Moreover, they use different herb oils and some extra ingredients (like garlic), increasing their potency against a large variety of insects.
- Not-Organic: these insecticides use chemicals, often manufactured in a laboratory, that mimic the natural ones but with stronger effects than their organic counterparts. Indeed, such insecticides use compounds synthesized (here the name) in laboratory scientifically designed to harm specific vital functions of some pests (respiration, for instance). Like their organic counterparts, many are the type of insects (and even animals) that one insecticide only can damage.
Tip: in case of necessity, you can use first a synthetic insecticide to get rid of the large bunch of pests and then continue the treatment with an organic version (either bought or DIY).
If you are particular environmentally-friendly and want to minimize your carbon footprint, then the organic DIY version is the way to go. Indeed, the industrial production of an insecticide (both synthetic or organic), their plastic (highly durable) packaging, and transport to the retailers, contribute to the emission of carbon dioxide in the atmosphere.
Moreover, on the safety side, it should not be forgotten that some synthetic insecticide should not be used in edible herbs. So be careful when buying one, check the label suitable for edible herbs as well. On the other hand, a DIY organic insecticide, done just with water, garlic, and mint, for instance, is totally safe to be applied to your herbs.
Herbs Against Bed Bugs
Bed bugs have not been analyzed before in this article as I found them a different category. Indeed, differently from ants and spiders are way less common (hopefully) in our daily life. Although, reading the NPMA bed bug survey highlighted that 20% of Americans have had (or still have) a bed bugs infestation. So the reason I am talking about it!
Such insects, typically brown (or translucent at their early stage of development) grow up to 7mm (although are generally smaller) and feed mainly on mammals’ blood and hair (human included). Even though bed bugs do not transmit diseases, they can cause minor skin irritations when they bite for feeding purposes. These small insects can be found not only on beds but also on couches and even on a bed-lamp.
The most effective against them are peppermint and lavender oil.
What herbs do spider hate? Among herb those that spiders avoid are peppermint, basil, mint, lemon balm, and lavender.
What herbs do slugs not eat? Many are the herbs that slugs and snails usually avoid, although not repelled. Among the most common there are chives, borage, chervil, lavender, lemon balm, mint