Neem Oil For Plants: What Is It And How To Use It?

Neem oil and neem berries in a mortar and pestle
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M. Kumar/Shutterstock
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How to Protect Your Plants Using Neem Oil as an Organic Insecticide

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Neem oil is a nontoxic pesticide that many gardeners say is their magic bullet to getting rid of bad bugs on plants. 

Known for its eco-friendly properties, you can make your own neem oil solutions at home or use commercial products. Homemade solutions tend to be more effective at protecting plants from harmful insects and diseases and are also cheaper. 

Read on to find out how to make neem oil for plants and how to apply it, and learn about some of its various uses and benefits.  

What is Neem?

branches from a neem tree
Related to mahogany, neem has been referred to as “Nature’s pharmacy.” Credit: Pixabay

Neem oil is extracted from the seeds of the neem tree (Azadirachta indica) and has been used as a pesticide for hundreds of years. It has also been a part of traditional medicine in some countries, where it is considered a cure-all for most diseases and ailments. 

In Indian mythology, it is said to be of divine origin and its Sanskrit name means “reliever of sickness.” It has been shown to have antibacterial and antiseptic qualities and is often used in soaps, cosmetics, toothpaste, and pet shampoo.

How Do I Use Neem Oil on Plants?

A few stems of neem leaves on a table with a bottle of pressed neem oil and a small bowl in the middle.
Neem oil and the neem plant. Credit: Shutterstock

Neem oil can be purchased as a ready-to-use spray or a concentrate that needs to be diluted first. Ready-to-use sprays can be used as they are, straight from the shop. Concentrated neem oil needs to be mixed with water and soap before use but can be a lot cheaper.

To be effective, the mixture needs to cover the entire plant. The best time to spray is in the early evening when the sun is low, and the bees are less active.

Neem oil can be used throughout the season, unlike many other pesticides that can be used only at certain times. It also affects insects at any stage of their life cycle and development. 

The only times to avoid using neem are in the midday sun (to avoid leaf scorch) and if rain is forecast for the upcoming 24 hours.

Neem oil is a natural botanical insecticide made of oil harvested from the tree’s seeds and has a low toxicity rating. It’s safer to use than a synthetic pesticide but still not totally safe. Follow the cautions on the label, and limit your exposure to the spray by wearing gloves, a mask, and eye protection. 

Steps to Using Neem Oil for Plants

A hand holding a green spray bottle, spraying a mixture onto a plant.
Spraying neem oil on plants. Credit: Shutterstock

Materials

  • A spray bottle
  • Protective gloves
  • 2 tablespoons of cold-pressed pure neem oil
  • 1 gallon of water
  • 2 teaspoons of dish soap

Step by Step Instructions

  1. Mix 2 teaspoons of dish soap with 1 gallon of warm water. Add it to your spray bottle and mix thoroughly.
  2. Add the neem oil to the bottle and mix again. Neem oil won’t mix well with water alone so needs dish soap to help out.
  3. Spray the neem oil solution onto your plant. Start at the top of the plant and cover all the leaves, both underneath and on top, until they are dripping wet. 
  4. After 3–4 days, apply the solution again. If you’re using it to remove insects and pests, continue use until the infestation has cleared. Neem oil solution can also be used as a preventative measure if you want to add it to your maintenance schedule bi-weekly.

How Does Neem Oil Work?

neem tree and white neem flowers
The neem tree has fragrant white flowers and fruits that look like small olives. Credit: Pixabay

The major active ingredient in neem is the chemical, azadirachtin, which is present in almost all parts of the tree but is most concentrated in the seeds. 

Like any oil, it suffocates bugs that get covered in it. It is most effective on immature insects and larvae. Adults may survive, so you need to time your application accordingly. It also works well on caterpillars, leafhoppers, whiteflies, mites, aphids, mealy bugs, thrips, and leaf miners and can kill eggs. It takes time to work; the effects are not immediate.

When the plant has been thoroughly sprayed, some of the oil will be absorbed, and it will act as a repellent to disrupt feeding by chewing and sucking insects.

It is also a growth regulator; neem can inhibit mating and impair the ability to reproduce, which will slow down an infestation.

As a fungicide, neem can prevent or stop fungal diseases, including rust, black spot, sooty mold, and powdery mildew. If the plant is already infected, it won’t cure what is there but will keep spores from spreading further.

neem oil spray in a white bottle with purple pansies and gold marigolds
Neem Oil spray can be found in almost all garden nurseries. 
Credit: Shutterstock

Top Tips for Using Neem Oil

  • Always make sure you dilute it properly, following the instructions above. 
  • Neem oil will only work if the pests are present when applying the solution. Unlike other pesticides that continue to work after application, neem oil breaks down quickly and has no effect once dry.
  • Test a leaf of your plant first to check for signs of stress over 24 hours before applying neem to the whole plant. 
  • Never use neem on plants that are already stressed (when they’re wilting due to lack of watering or after transplanting).
  • Avoid using neem oil for plants in the middle of the day because this could lead to leaf scorch.
  • Make sure you cover the whole leaf—even the underside. 
  • Mix a new solution every time you want to use it; the mixture can thicken over time and become difficult to spray.
  • Don’t spray on new plants; this could burn tender new growth.

Neem Oil Cautions

While this oil is a fantastic, nontoxic way to rid your garden of pests, it can also harm the beneficial insects! Use caution when applying neem oil, focusing on the areas of infestation, not broadly spraying each affected plant.

Neem oil is toxic to bees that are exposed to direct treatment, so please don’t apply it if they are present. It is harmful to fish and aquatic mammals, so do not use it near water. 

Avoid using it directly on beneficial bugs and butterflies. It is not harmful to pets and livestock, but you should take care that they don’t ingest it. 

If you’re using neem oil on fruit and vegetables, make sure you wash them well before eating. 

Also, don’t use neem oil on plants that are already stressed. The oil degrades quickly so you will have to reapply it as often as every 7 to 14 days or as directed.

Neem Oil FAQ

How long does neem oil take to dry?

If the plant is thoroughly wet with neem oil, it should take around 1 hour to dry.

Does rainwater wash neem away?

Yes! So avoid using neem just before rain is forecast. 

How long does a bottle of neem oil last?

Store-bought bottles can last up to a few months, whereas solutions you have mixed yourself should be used on the day you mix them.

Are there any plants to avoid using neem oil on?

While neem is a versatile and natural pesticide, you should avoid using it on delicate or soft-leaved plants such as fuchsia, succulents, cacti, and any newly transplanted or young plants. 

Neem Oil For Plants: Summary

In conclusion, neem oil is an eco-friendly solution for maintaining plant health and controlling pests and diseases. By applying this oil correctly, you can protect your plants and cause minimal damage to the environment and beneficial insects. 

Do you use neem oil? Please share your experiences below! You can read more about other natural solutions used in the garden, such as Epsom Salts.

About The Author

Robin Sweetser

Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. Read More from Robin Sweetser