If you are trying to limit your exposure to toxic and synthetic chemicals in your garden and home essential oils can be valuable tools. They are well-known for their wellness virtues for humans, and can also be precious allies to protect your plants naturally and ecologically.These oils have been used for thousands of years for their medicinal and cosmetic benefits, and their power lies in the hundreds of chemical constituents they contain. Whether you are trying to chase away garden pests from your vegetable or flower garden, protecting your plants against diseases, or you simply want to improve their overall health, you can use these natural defences to your advantage, using products you can store in your medicine chest. How cool is that!
Benefits of Essential Oils in the Garden
Essential oils are the volatile liquids extracted from plants through steam distillation. Their power lies in the hundreds of chemical constituents they contain. Each oil profile has anywhere from 200 to 800 different constituents in varying amounts, hundreds of which have yet to be identified and studied by scientists. Scientists also believe that because of the complex combinations of their constituents, pests will build up a resistance more slowly to essential oil-based pesticides than their synthetic counterparts.
Research has focused on agricultural crops with results showing that essential oils effectively combat a wide range of pests and diseases of agricultural crops, and they also work in ornamental gardens, home vegetable gardens and orchards, making them a natural and ecological alternative to chemical pesticides.
Essential oils offer highly concentrated, natural solutions for organic gardening. They act as potent, Broad-spectrum Pest Repellents, Insecticides, and Fungicides, and unlike chemical pesticides that can damage beneficial insects and degrade your soil health, essential oils won’t harm your soil or pollute the environment.
The most important benefit of using essential oils is that they are safer for humans and beneficial insects. Pollinators are also less likely to suffer, but gardeners must still be careful not to spray essential oils directly onto beneficial insects like bees.
Recent studies indicate that some of the chemicals in essential oils interfere with the octopaminergic nervous system in insects, and since mammals do not share this target site, most diluted essential oil garden sprays will be non-toxic to gardeners and their fur babies.
However, it’s always best to be cautious around pets when spraying or diffusing, as some essential oils are dangerous for pets if inhaled or absorbed through the skin, and even though you are diluting your oils with water to spray your plants with, it’s still safest to keep pets away.
How do pests magically find my plants overnight?
How pests find your precious plant’s is quite magical and ‘mother nature’ at her best!
What are Pheromones and VOC’s?
When pests look for victims, they don’t just randomly choose any plant; they choose it based on specific chemical signals coming from their favourite plants. These signals are called “pheromones” which act like GPS right to your plants.
Plants don't produce true pheromones in the zoological sense, where pheromones are strictly chemicals used for communication within a single animal species. Plants produce highly complex Volatile Organic Compounds (VOCs) and hormones that act in remarkably similar ways to humans, allowing them to communicate, defend themselves, and even manipulate other members of the same species.
For example, if a branch is attacked by insects, it can send airborne signals that prompt other branches, and even neighbouring plants of the same species, to produce defensive toxins before they are even attacked. Some plants can even call for help when attacked, and when one plant is eaten by a caterpillar, it releases specific chemical distress signals that act like an alarm, attracting parasitic wasps or predatory insects that hunt the exact caterpillars damaging the plant.
Pheromones are generally odourless or have a faint, subconscious scent, often described as musky, slightly sweet, or earthy. In nature, different chemical signals have distinct traits—some smell like vanilla, while others smell like rotting flesh, and even urine or sweat in order to attract pollinators. Many flowers like orchids will mimic the exact sex pheromones of female insects to trick the male insects into attempting to mate with the flower. This ensures the plant is pollinated without having to provide any food or nectar.
Pheromones in plant life are called “semiochemicals” and these naturally occurring, organic chemical signals facilitate communication within a species and play a crucial role in various ecological interactions. Released into the environment, these chemical signals can be interpreted by other members of the same species, influencing their behaviour and physiological responses. Acting as nature's non-verbal communication, these highly specific compounds are widely utilized in sustainable agriculture as eco-friendly alternatives to traditional chemical pesticides.
For example, pheromone traps are widely used by farmers today as they are very effective in monitoring or disrupting the mating cycles of destructive insects. You can utilize these chemical concepts in your own garden or farm, as highly fragrant oils work in a similar manner, masking the smell of the crops and other plants they are protecting, confusing unwanted insects, and sending them on their way because your plants are not an easily recognizable target.
Companion Plants and Essential Oils
Both companion planting and intercropping to add biodiversity to the planting is a favourite method of organic gardeners because it offers a hands-off approach to pesticide use.
Pest are attracted to crops by their scent, so by planting many varieties of flowers, vegetables, fruits and other beneficial plants together, their pheromones are mixed, creating a cocktail of chemical scents that confuses pests.
If you combine high-intensity spacing with intercropping you will not only prevent pests from detecting their favourite snacks, you will also grow much more food in a given space.
If you have a small garden and don’t have space for all the companion plants you would love to grow, essential oils can be used instead. For example, basil is a great companion plant for tomatoes, so spraying basil essential oil onto tomato plants is very beneficial. You can even apply it as a soil drench to give the plants a dose that can be absorbed through the root system. This helps to give the tomato plant vigour and greater resistance to pests and diseases.
To Attract Pollinators
To attract pollinators naturally to your edible garden, put 10 drops of wild orange or lavender essential oil into 250ml water, agitate and spray lightly over flowers and buds. Repeat frequently.
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How to Use Essential Oils for Pest Control
When it comes to organic gardening, as with humans, prevention is better than cure, and spraying crops regularly with essential oils to prevent insect infestations and diseases is the most effective method. This will not only chase pests away, but also make your garden smell great!
Always use pure essential oils, and because they are so potent, always dilute them first.
How to dilute essential oils
One of the drawbacks of using essential oils in the garden is that the levels of terpenes and other constituents can vary greatly depending on the region where the plants are grown, genetics, climate, soil, and other seasonal factors. Therefore, maintaining consistency in the chemical profile of the oils is hard.
For example, rosemary oil extracted from plants growing in two different regions of Italy will contain varying levels of α-pinene, ranging from 11% to 36%. Another study showed that essential oils extracted from different chemotypes of garden thyme did not have the same toxicity against the bean weevil.
This is the reason why, if you look for exact recipes for the oil you wish to use in the garden you will find many different quantities of oil versus water used.
Another factor to take into account is the actual number of drops in a millilitre can vary greatly depending on the thickness of the liquid: Thicker liquids like essential oils produce larger drops, meaning it takes fewer drops to make 1mL. Different dropper bottles or droppers also have varying nozzle sizes, which changes the volume of a single drop.
In standard pharmaceutical measurements, 1 mL is equal to approximately 20 drops (meaning 1 drop is about 0.05 mL). Therefore, 10 drops are typically equal to about 0.5 mL.
This is why physicians do not rely on counting drops, as this can lead to incorrect dosing. Instead they use an oral syringe, a graduated measuring cup, or the specific dropper provided with the medicine.
Because the actual number of drops in a millilitre can vary greatly depending on the thickness of the liquid and varying nozzle sizes, which changes the volume of a single drop, I recommend starting with the lowest recommended dosage. You can always increase it later.
Always Test Sprays First:
Because the strengths of essential oils can vary, to ensure it does not cause leaf burn (phytotoxicity) it’s important to always test your spray on all the plants you wish to spray, as certain plants may be more sensitive than others. To check spray small, isolated areas of the plants first. Wait at least 24 hours to check for damage before applying it everywhere.
TIP: Tie a piece of string onto each branch you have sprayed so you will remember which plants you have tested.
Mixing your garden spray:
Because essential oils are incredibly strong, to prevent burning your plants always dilute them in water first.
For protection start with only 5-10 drops per Litre of water,
At certain times of the year various pests and diseases will be more prevalent, so for stronger protection dosages can be increased.
Generally you will find recommended dosages are between 10-20 drops per Litre of water.
The Emulsifier:
An emulsifier is essential as essential oils do not mix with water and will float to the top, potentially burning your plants. A gentle liquid dish soap, pure liquid Castile, or black soap can be used. Witch hazel, vodka, or apple cider vinegar also emulsifies oil and water.
Approximately one teaspoon of liquid emulsifier is used in one litre of water.
The Method:
In a small container, mix your essential oils with your emulsifier, then add some of the water and stir well. Warming the water helps with emulsification. Add the oil mix to the spray bottle with the rest of the warm water. Agitate well before and also regularly whilst spraying.
Applying your Oils:
Spraying in the middle of a hot, sunny day can magnify the sun and cause leaf burn, so always
apply the mixture in the cool of early morning or late afternoon. Remember to agitate the spray bottle well before use, and regularly while spraying. Ensure that you spray underneath the leaves where insects commonly hide.
During the cooler times of the day beneficial daytime pollinators are not that active. Never spray plants if you can see beneficial pollinators like bees around the plants. Even organic sprays can be abused in the garden, so as they say “everything in moderation”.
NOTE: The strength of the oils will evaporate, so reapply to plants after rain, every week for protection, or every couple of days, as needed.
Storing Essential Oil Mixes
Try to mix up only sufficient spray to use in a day, or within 24 hours of mixing. Once exposed to water and oxygen, oil-based garden sprays begin to separate, degrade, and lose their effectiveness.
If you do have any left-over, store it in a glass bottle in a cool, dark place, not in your plastic spray bottle, as essential oils break down in plastic. Agitate well before using again.
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Methods of applying Essential Oils
Garden Spray:
Mix 10-20 drops of Essential Oil in 1 Litre of water with an emulsifier. Shake well, and regularly while spraying down the foliage of plants. Make sure you get underneath the leaves where pests like to shelter, and lightly spraying the soil around your plants will also help.
Drenching:
Some essential oils are recommended for drenching the soil around plants to keep them healthy. This allows the roots to absorb the nutrients naturally. Chamomile and Basil are good examples.
For drenching 8-10 drops of essential oil is mixed into a 5L watering can and agitated vigorously before drenching the soil. A drop or two of gentle liquid soap can be added to help it emulsify.
Cotton Ball Method:
To target specific insects in large numbers, like ant hills or rodent burrows, take some cotton balls and add a few drops of essential oils to them. Next, place the cotton ball right onto the ant hill, burrow or other insect grouping. This will cause them to relocate immediately. If that doesn’t work immediately you should repeat the process using a stronger solution.
You can also rub the oils onto any hard surfaces regularly to create a long-lasting barrier.
Deter Slugs and Snails
Bury a small glass container into the soil so its rim is perfectly level with the ground. Add 3-4 drops of pine oil into the container. The scent is highly offensive to slugs and snails, keeping them away from your prized plants. Renew the oil after heavy watering or rain.
Post-Harvest Protection
Fumigation:
Essential oils are heavily researched today for their potential in keeping stored agricultural crops pest free. Results show that they can be introduced to sealed storage containers to deter pests and affect adult development of agricultural storage insect like weevils and beetles. For smaller storage spaces the oils can be diffused in the room.
Protection:
Add a few drops of pure essential oil to porous clay pucks or sachets and place them inside sealed storage containers. The released fumes safely repel beetles and other pests without diminishing seed viability or germination rates.
Impregnating storage bags with parsley essential oil has been studied as a tool to manage and repel crop-destroying insects of stored agricultural crops, without using harmful chemical residues.
The cotton wool method and diffusing, as described above, is also effective in pantries and small storage spaces.
Is there a waiting period before harvesting?
You should not eat vegetables and fruits immediately after spraying them with essential oils. These oils are highly concentrated and consuming them without a waiting period or proper cleaning can cause digestive upset, inflammation, or irritation of the mouth and oesophagus.
Essential oils degrade in sunlight and waiting 24 hours should be sufficient. Ensure that you always wash your food well and all will be fine.
Can I use a diffuser indoors if I have pets?
Pets have highly sensitive respiratory tracts, so if you are diffusing essential oils in the home, purchase an ultrasonic water-based diffuser, as the nebulizing models spray micro-droplets of oil which can trigger respiratory distress in pets, and can cause coughing, sneezing, or asthma flare-ups. If micro-droplets land on a pet's coat and are ingested when they groom themselves, it can cause toxicity upon ingestion. Birds and cats are especially at risk.
How to diffuse safely
Ensure that your diffuser is in a place where your pet cannot knock it over and potentially expose themselves to the oils.
Diffuse in moderation, using only a few drops (3-5) of essential oil in a water-based diffuser, and run the diffuser for short periods of no more than 30 minutes. Keep- spaces well-ventilated and ensure that your pet can easily leave the room if the oils are irritating them.
Avoid certain essential oils:
Completely avoid toxic oils such as Wintergreen, Tea Tree, Eucalyptus, Cinnamon, Clove, Peppermint, Citrus, and Pine which are highly toxic to both cats and dogs, and can result in organ failure or seizures.
Non-toxic essential oils for pets
When diffusing essential oils around pets stick to options that are not toxic to pets like: Lavender, Frankincense, and Chamomile.
For dogs: Lavender, Bergamot, and Sandalwood are generally safe when used in low concentrations and if they are well-dispersed in the space. These oils have a calming effect and can help reduce stress.
Warning Signs:
If your pet shows symptoms of essential oil toxicity—such as drooling, vomiting, wobbling, or tremors, seek immediate veterinary care.
In Conclusion:
I cannot guarantee you a 100% pest-free garden, but using essential oils for pest control will allow you to have at least a 90% pest-free garden 100% organically!
When used in conjunction with other organic gardening methods, essential oils promote the obtainment of healthy, bountiful harvests without toxic residues, while respecting the environment and the garden's biodiversity.
If you’re looking to promote healthy growth in your garden, a good starting point is ensuring your plants have good soil and the nutrients they need. Plants also need to be watered correctly, as a water stressed plant is vulnerable to attack, and overwatering encourages fungal diseases. Good gardening practices, used in combination with essential oils, can help create a vibrant, thriving garden that’s naturally resistant to pests and disease.
The last bit of advice is to just give different essential oils a try. You may find that one type works better than others in different areas of your garden. With a little patience and testing in the garden, you will find something natural and non-toxic that suits both you and your plants.
I hope this article has inspired you to treat yourself and your plant family to the wonderful benefits of essential oils.