Infinitely useful, neem oil for plants is a great solution for a number of problems. Providing a safe, chemical free way to treat everything from fungal problems to infestations, this is a safe solution that won’t harm plants or animals or even wildlife. If you want to start reaping the benefits of using neem oil for plants in your garden, this article will explain everything that you need to know.
Using neem oil for plants has many benefits such as providing a safe but effective way to treat infestations.
What is Neem Oil?
Before explaining how and why you should use neem oil for plants I will first take a few minutes to explain exactly what this useful substance is. Simply put neem oil is made by pressing the seeds of the neem tree. A versatile substance, it can be used for plants, medicines and in the cosmetic industry.
The neem tree, Azadirachta indica, is a stately broadleaf evergreen, indigenous to the South Asian subcontinent. A member of the mahogany family, mature specimens can reach over 90 ft tall.
Why is Neem oil for Plants so Beneficial?
Azadirachtin is present as an active component in neem oil. This chemical compound is the main reason why it is so beneficial for plants. Azadirachtin reduces the levels of insects feeding on foliage. A reliable insect repellent azadirachtin can also interfere with insect hormones, deterring egg laying and interfering with the growth and development of young insects.
In addition to Azadirachtin, neem oil also contains Omega 3, 6, and 9 fatty acids. It has a half life of 3 to 22 days in soil but only 45 minutes to 4 days in water.
The flowers of the Azadirachta indica. As the flowers fade, seeds emerge. These can be pressed to produce neem oil.
What are the Benefits of Neem Oil for Plants in my Garden?
Technically classed as a miticide, neem oil is useful in treating a number of insect infestations while leaving beneficial insects such as lady beetles and bees unharmed.
Once made into a foliar spray, I will explain how shortly, and applied to the leaves of a plant it kills any pest that eats the foliage. Beneficial insects and pollinators do not eat the leaves, meaning that they are unharmed by the solution.
Using neem oil for plants is a great way to treat infestations of a number of common garden pests, including:
- Japanese beetles,
- Moth larvae,
- Spider mites,
Like insecticidal soap, this is an effective treatment which is safe to use on a range of different garden flowers, fruits, vegetables, shrubs and even trees. For example, fruiting specimens such as tomatoes and peppers, flowers such as roses and nasturtiums and even trees such as Colorado blue spruce trees are all prone to aphid infestations. A single foliar neem oil spray is safe to use on all these different specimens, and many more.
Not only does it provide a safe way to control infestations it also has fungicidal properties. This means that it can be used to treat fungal problems such as powdery mildew on both flowers and trees. Some specimens, including the flowering dogwood, many different citrus trees and flowering vines such as passionfruit can be particularly susceptible to this issue. Here, a regular application of a neem oil based foliar spray is best used as a preventative measure. It can also be used to prevent more specific diseases such as Cooley spruce gall adelgid.
Finally, a foliar spray is also a good way to protect young growth from infestations or disease.
What is a Foliar Spray?
As I have already mentioned, one of the most effective ways to use neem oil for plants is with a foliar spray. This is a spray that can be sprayed onto the stem, leaves and flowers of a plant. You can either purchase a foliar spray or make your own.
If used correctly this is a safe, non-toxic solution. But be sensible. If you are using a purchased product always read the label before use and follow the instructions. Clean items and wash your hands after using the product. In some cases neem oil can irritate sensitive skin, if you are concerned wear gloves when handling the product.
Some shrubs and flowers can be killed by foliar sprays. Especially if it is heavily applied. Before treating an entire plant, spray a little of the solution onto one or two leaves. Wait 24 hours before checking for leaf damage. If there is no visible harm to the sprayed area it is safe to treat the entire specimen.
Apply sprays only when the affected specimen is in indirect light or, if planted in full sun, in the evening. This helps to avoid burning foliage. Treating during the evening gives the solution time to seep into the plant before it is evaporated by the heat.
Avoid applying foliar sprays and solutions during periods of extreme temperatures or to stressed plants. Particularly if the plants are stressed due to drought or over watering.
Avoid treating foliage during the heat of the day. Wet foliage is prone to burning under the heat of the sun.
How to Make a Foliar Spray
While you can buy commercial products containing neem oil for plants, you can also make your own.
You will Need:
- 1 gallon of fresh water,
- 1 tablespoon concentrated cold pressed neem oil,
- 1 teaspoon of liquid soap or pre-wetted silica powder,
You can also add some aloe vera powder, no more than ⅛ to ¼ of a teaspoon, or a few drops of essential oils. Some essential oils, such as aloe vera can help to boost the immune system of the plant. Peppermint is also a popular choice for foliar solutions because its odour is unappealing to many pests. This deters them from targeting your foliage. Lavender, tea tree, eucalyptus and orange are also good choices for their natural insect repellent qualities.
Before making the solution you need to emulsify the neem oil. Failure to do so means that it won’t properly mix with water. Even when fully emulsified, the solution still separates over time. If you have made a large batch and stored some of it for future use, shake thoroughly to remix the solution before using it. However, many people find it easier to make smaller batches each time, especially if you are also using essential oils such as aloe vera. Solutions containing essential oils need to be used straight after mixing.
To emulsify, use either liquid soap or silica as an emulsifying agent. While either can create an effective foliar spray, silica has some additional benefits. Firstly silica helps plants to increase their tolerance to stress and drought. Silica can also help to strengthen cell walls, leading to stronger stalks and plants. Finally, solutions containing silica better coat the leaves. This makes them less susceptible to fungal diseases such as powdery mildew and also deters small sap sucking insects.
While silica has many benefits, liquid soap is just as efficient as a way to treat pest infestations. Spraying some liquid soap mixed with warm water is my go to method for treating aphid infestations on my rose bushes.
While you can’t make a large batch of the foliar spray you can pre-mix the silica powder with water and store, ready to mix with the emulsified solution as and when you need it. To do this combine 35 grams of silica powder to 8 ounces of water. Mix the solution thoroughly. Once combined, label the jar and store in a cool dark place. In this condition the solution keeps for up to a year.
To emulsify you will need a small container, such as a half pint jar. Add 1 tablespoon of neem oil to 1 teaspoon of liquid soap or pre-made liquid silica solution. Stir well. When properly combined the mixture will be a thick, creamy yellow liquid.
To make the foliar spray, fill a pump sprayer with no more than a gallon of fresh water, a quart shy is ideal. Scale the amount up or down depending on how many plants you are treating.
Add any essential oils if you are using them. Put the cap on and shake well, thoroughly mixing the solution.
Fill a clean quart jar ¾ full with warm water. The water must be warm, not hot. Add the emulsified solution to the warm water. Secure the lid on the top of the jar. Shake well, ensuring the solution is properly combined. Once fully mixed no oil droplets should be visible. Add the solution to the water already in the pump sprayer. Shake well to mix.
If you are only treating a few plants, or applying the solution to your collection of houseplants, make up a smaller amount of the spray in a clean spray bottle such as the Rayson Spray Bottle.
How to Apply the Foliar Solution
Remember to wear gloves when applying the foliar solutions. Some people can get a mild dermal reaction or allergy from the solution. Gloves also stop your hands from getting covered in oil.
Don’t spray small seedlings. The solution may burn their leaves. Wait until plants are a few months old before using a diluted version.
The foliar solution is best applied on a cloudy afternoon or as the sun goes down. The latter is preferred because beneficial insects are less likely to be active at this time of day. A late afternoon or early evening application also gives the spray time to work and dry before the sun comes out.
Never apply sprays or liquid solutions in the middle of the day or during sunny weather. Wet foliage is more likely to burn under the sun’s intense rays.
Try to cover the plant as evenly as possible. This is easier when treating smaller specimens than taller trees and shrubs.
How Often Should I Apply the Solution?
Never apply a foliar spray more than once a week. However, for long lasting protection the solution does need to be applied on a regular basis. This is because while it is effective it doesn’t have a long lasting residual effect.
If you are protecting plants such as artichokes, spray once a week or once every other week. This same frequency can be applied to plants showing early signs of infestation or disease. Other, larger specimens such as citrus trees can be treated once a month.
Treat specimens regularly for maximum benefit. When treating young plants, dilute the solution as much as possible.
Using Neem Oil for Plants as a Soil Drench
A soil drench is a solution that soaks into soil. Here it is absorbed by the root system and distributed throughout the plant tissue. Once in the vascular system the neem oil compounds cause the number of feeding insects, such as aphids, mealybugs and scale, to reduce significantly. In some cases the oil coats the breathing holes of insects, suffocating them.
A soil drench is also a useful way to defend plants against root rot and soil dwelling pests. Used in this manner a soil drench solution is particularly useful for tomatoes that are susceptible to soil borne nematodes.
What You Will Need:
- One tablespoon of cold-pressed Neem oil,
- One teaspoonful of liquid soap,
- One quart of warm water.
How to Make a Soil Drench Solution
A soil drench solution is easy to make. Simply combine the ingredients evenly in a watering can. Shake or stir well.
Pour the combined solution into the soil around the plant. Try to soak the soil as evenly as possible.
Apply the solution once a week if treating an infestation or once a month as a preventative.
Evenly soak the solution into the soil around the plant.
Finding a safe non-toxic pesticide that actually works can be difficult. Especially one that doesn’t harm beneficial insects, people or the environment. If used properly, this is a reliable insecticide that does exactly what you need, killing and deterring pests and preventing disease while leaving no potentially harmful residual trace behind. Used correctly it enables beneficial insects to thrive and the soil to stay chemical free while also keeping your plants healthy and happy. Why not start using neem oil for plants in your garden today?
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.