How to Use Neem Oil on Houseplants
What Is Neem Oil?
Neem oil is one of the most effective natural ways to treat pests on houseplants. It can deal with common insects like Spider Mites, Aphids and Fungus Gnats, while also helping prevent future infestations. But it only works properly if you use it the right way.
Neem Oil comes from the seeds produced by the Neem Tree (Azadirachta indica), a fast-growing tree native to the Indian subcontinent. It has many uses, from skincare to neem cake fertilizer. With plants, it's typically used as an organic insecticide whenever pest infestations occur. It's especially useful to anyone looking for a cheap natural alternative to synthetic pesticides.
Seeds of the Neem Tree (Azadirachta Indica) by Qniemiec.
My article will tell you everything you need to know about Neem, how it works and is used to benefit and protect your plants. I also have a recipe for a DIY homemade spray.
Quick Answer: How to Use Neem Oil on Houseplants
To use neem oil on houseplants, mix 5ml (1 teaspoon) neem oil with 1 litre of water and a few drops of liquid soap. Spray all leaf surfaces every 5-7 days, avoiding direct sunlight. Repeat for several weeks until pests are gone.
How does Neem Oil work?
Neem Oil is a natural pesticide and when it comes to controlling pests, it works in four broad ways.
- Anti-feedant
It stops the insects from feeding on the plant, so they eventually starve. - Stops Reproduction
The compounds within the oil slow down or stop the pests from reproducing by altering their hormones. Putting an end to their reproductive cycle and therefore reducing large infestations over time. - Contact insecticide
Pests sprayed directly will be smothered by the oil. - Repellent
Other compounds within Neem will repel pests and some diseases, protecting your houseplant from further problems.
What Pests and Problems Does Neem Oil Help With?
When used correctly, Neem Oil has a range of applications and can help you tackle a wide range of problems.
- Most pests that feed off plants
It will work on the majority of common pests that feed off houseplants. Including Aphids, Fungus Gnats, Mealy Bugs, Scale Insects, Spider Mites and Thrips. - Some diseases
It's also effective if your plant is suffering from diseases caused by fungi, such as Powdery Mildew, Rust, Leaf Spot and Black Spot.
- Insects that only live on your plants or in the soil
To be effective, the pests need to consume your plant to ingest the Neem compounds. Pests which only live on the plant or within the soil are unlikely to be affected. Centipedes, Millipedes and Springtails are good examples of these.
This is normally considered a benefit, though, as it means it's not targeting insects that aren't damaging your plants and does not harm beneficial insects.
Neem Oil vs Other Pest Treatments
- Neem oil vs chemical pesticides.
Neem oil works more slowly, but it's much safer for indoor use and less harsh on people, pets, and plants. - Neem oil vs insecticidal soap.
Insecticidal soap works on contact, whereas neem oil also disrupts insect life cycles, giving it longer-lasting effects.
Hi, I'm Tom!
If you're like me and enjoy the challenge of growing houseplants and getting them to thrive, then OurHouseplants can help. This website shares my knowledge and years of growing plants and provides my advice on properly caring for your indoor plant friends.
7 Things to Know Before Using Neem Oil
After reading this far, hopefully, you're feeling optimistic about the benefits of using Neem. And so you should! For many people (including me), it ticks lots of boxes and is an effective product and natural solution for common houseplant pests.
Of course, as with anything, there are some important things to consider and be aware of. Here are seven things to know.
When used correctly, neem oil is a powerful insecticide.
- Works slowly.
Many people will have excellent results using it. But it's not an instant fix and takes time to do its thing. You need to have patience and potentially apply the treatment over a few weeks. - Can leave a shine.
An added benefit is that the oil will create a natural-looking leaf shine effect on sprayed plants. (If you're not a fan of this, you can remove some of the shine by using a damp cotton ball or microfiber cloth). - Mix fresh batches.
A significant component of neem oil is Azadirachtin. When the oil is mixed with water Azadirachtin quickly loses its strength. Studies show it can break down between an hour and four days after mixing.
This means in most cases; it's far better to mix small fresh batches when needed and don't store any leftovers for long periods. - Avoid direct sun.
Sunlight will also rapidly reduce its effectiveness. To stop this happening, don't apply Neem oil to plants in direct sunlight and ideally keep them away from it for at least a couple of days.
If this isn't possible, apply in the evening after the sun has set. - Strong smell.
Horticulture grade 100% Cold Pressed Neem Oil, has a powerful odor, like garlic and sulfur mixed with a bit of rotting onion. Most people don't like it. The scent surrounding the plant will fade a lot once the spray has dried on the leaves (after an hour or two). - Use carefully around people and pets.
Studies show Neem is not particularly harmful to human health, especially when used in the low concentrations you find in homemade sprays. Certainly less damaging than commercial pesticides.
But be sensible. Keep it out of your eyes, wash your hands after use and keep kids and pets away. - Keep away from flowers and beneficial insects.
When used correctly, it will only affect insects that are sprayed directly or those which eat parts of your houseplants.
Therefore if you don't take care with it, beneficial insects can be harmed. Additionally, if you apply it to flowers, these beneficial insects might consume the pollen and nectar later.
Where to Buy Neem Oil and What to look out for?
As we've explored above, the oil is extracted from the seeds produced by the Azadirachta indica tree. Like with many oils, it can be extracted from these seeds in multiple different ways. The method of extraction used determines what you're getting. In the majority of instances, the product you buy will be one of the following.
- Clarified Hydrophobic Extract
- Azadirachtin Extract
- 100% Cold Pressed
The first two, Clarified Hydrophobic Extract and Azadirachtin Extract are by-products created after the seeds have been highly processed. This might be acceptable for certain general uses such as in cosmetics. But this is not good for our intended use as an insecticide.
This is because many useful biochemical compounds and active ingredients have been removed and its effectiveness reduced.
Value for Money
You will only use a small amount each time you mix up a spray. So a bottle should easily last you for years, even with regular use.
100% Cold Pressed therefore is hands down the best you can buy, and what you should be looking for. It can be a little more expensive, but you'll get significantly better results in return.
Most garden centers will usually have it for sale, but if you're not keen on hunting around for the cold pressed version (or can't find it), Amazon's got you covered (links to some highly rated products below).
#ad
#ad
How to Make a Neem Oil Spray
If you want to make your own neem oil spray, you only need a few ingredients and a spray bottle. Mix fresh each time, because neem loses strength after it is diluted with water.
Covering my Rhaphidophora Tetrasperma (Mini Monstera) with a homemade foliar spray.
This "recipe" will give you just over one liter of product which is probably more than enough to thoroughly treat a good number of plants in one go.
As mentioned earlier, the potency will rapidly decay once mixed up, so feel free to scale down (or up if necessary) the amount of ingredients if this volume is too much (or not enough) for your needs.
Ingredients
- 5ml (1 teaspoon) Neem Oil
- 1ml (1/4 teaspoon) Liquid Dish Soap or Liquid Horticultural Soap
- 1,000ml (1 liter) Warm Water
Method
- Pour the warm water into your spray bottle. The water should be warm to help everything mix together better. Avoid hot water as this can damage your plant's leaves.
- Don't fill it more than 75% full as you'll need to add the other ingredients and need a little space for mixing.
- Add the Neem Oil and Liquid Soap to the water.
- All three ingredients at this point will separate. You need to blend them together by shaking the spray bottle hard for 10 seconds or so.
- Your homemade spray is ready to use immediately.
- The liquid soap will help keep the oil emulsified, but you'll still need to keep shaking it again every minute or so while you're using it, to ensure the mixture stays blended.
How to use the spray
The goal is to thoroughly spray your plant until you've applied an even coating of the mixture all over the leaf surface. This will mean covering both the upper and underside of the leaves, which is often where insects will be hiding.
All of this spraying can pool on the leaf edges, which then drip onto whatever's below. You might also accidentally spray a little onto the surrounding surfaces.
Shelf - Life
Neem Oil's potency will rapidly decay once it's blended with water. The spray will keep for a day or two, at which point it will be better to mix up a new batch for maximum results.
Neem Oil doesn't typically stain or damage surfaces, but there is always the chance it could. It also smells quite strongly, so I gather all the plants to be treated and move them outside out of the way. This might be something you'd like to consider doing too, in order to avoid the above issues.
The leaves will dry off within a few hours at which point the strong smell should have dissipated (or at least reduced!). During this period, make sure you keep your plant out of direct sunlight because 1) The mixture can cause the sun to burn the leaves and 2) Sunlight will break down the Neem compounds and reduce its effectiveness as an insecticide.
You only need three simple ingredients to make an effective homemade neem oil spray.
Can You Use Neem Oil as a Soil Drench?
Some pests live in the soil where sprays can’t reach. Fungus gnats are a good example, as they lay eggs in the compost and spend part of their life cycle there. In these cases, a neem oil soil drench can help by targeting pests below the surface.
When used this way, the plant can also absorb some of the active compounds. This means insects feeding on the plant later may still be affected, giving short-term systemic protection. To apply it, simply pour your diluted neem mixture into the soil as if you were watering. Make sure excess liquid can drain away freely.
Always Do a Patch Test First
Usually, when used in low dosages, Neem Oil won't harm your plants. I recommend doing a "patch test" first as it's always possible a certain houseplant may react negatively.
Using as a soil drench is much more potent for the plant, so only do it after you've given spraying a try first.
While effective, soil drenches should be used with caution. Neem oil has antifungal and antibacterial properties, which means it can also affect the beneficial microorganisms living in the soil.
These microbes often support plant health, so disrupting them may reduce some of those benefits. Addtionally studies show that it's likely that some of the air cleaning abilities of plants and the ability to remove toxins from the air comes from the microorganisms in the soil.
For these reasons, a foliar spray is usually the better first option. Use a soil drench only when spraying isn’t practical or hasn’t solved the problem.
Quick takeaway
Foliage Spraying should produce excellent results over time. A Soil drench, whilst also very effective, can have negative consequences so should only be used as a last resort.
Neem Oil FAQs
Neem Oil mixing ratio
The standard neem oil ratio is 5ml (1 teaspoon) per 1 litre of water, plus a small amount of liquid soap to help it mix.
How often should you apply neem oil?
Apply neem oil every 5 to 7 days for active infestations. For prevention, use it once every 2-4 weeks.
Where to buy neem oil for plants?
It's important to buy as pure as possible. This means you know exactly what you're getting and can be sure you'll get the best results while treating your plants. We cover this in more detail here.
What's the difference between Azadirachtin vs. Clarified Hydrophobic Extract of Neem Oil?
This can be a confusing topic, but it's important to get it right. So we've covered it here.
Is neem oil safe for humans?
In low diluted concentrations, neem oil is normally very safe for humans and pets alike. Still take precautions, and wash your hands after use.
The undiluted oil can cause harm if ingested so you must keep it sealed and out of reach from kids and animals.
Can it be used on plants I'm going to eat?
Theoretically, you can use it on all your indoor plants or herbs (and outdoor ones too, even ones you plant to eat). It can be sprayed on fruit trees and vegetables with no issues. However, the oil has a strong taste that could impact the flavor. So it's probably best to treat edible plants several weeks before you intend to harvest anything from them.
How to use neem oil on houseplants for gnats?
As fungus gnats live part of their life under the soil, you will need to treat the soil to ensure you get them all. Read our Soil Drench section for a how-to.
How to prevent pests on indoor plants?
Fortunately, pests problems aren't too common for most indoor gardeners. But if for some reason your plants are very prone to pests, you can use our basic spray mixture as a preventative measure. Simply use the spray lightly once a month and this should repel most insects.
When should I apply it?
The effects are diminished when exposed to sunlight so it's best to apply it either very early in the morning or late at night.
How often can it be applied to plants?
You can reapply the spray around five days after the previous application. You might still notice insects crawling around a few weeks later. This can be unbelievably frustrating and you might even think the neem's not working. Don't drastically increase the concentration, continue to apply conservatively every four or five days and be patient as the effects take time to work.
How long does it take for neem to work?
Although the spray will start to work as soon as it's applied, it will generally take at least a week or two before you see positive results. It could be a couple more before your plant is completely clear. Bear with it though. Neem will normally have good long-term results and a degree of pest resistance from future issues.
What plants is neem oil not good for?
Some houseplants will have a sensitivity to neem. Other plants may also have a sensitivity to the dish soap. We recommend doing a patch test on a leaf and waiting a few days before spraying the entire plant.
Some plants should not be treated with neem / dish soap at all. Don't use it on any carnivorous plant like the Sarracenia or Venus Flytrap. Take extra care with more fussy houseplants like Ferns, which can respond poorly to any spray, whether its synthetic or natural.
Why are my plant's leaves turning yellow after application?
If it's not been applied to a "sensitive" plant listed in the previous question, then it's likely you've used too much of the oil in the mixture. Pure neem oil is potent and concentrated stuff, you really don't need to use a great deal for effective results.
The rapid yellowing and excessively shiny leaves on this Parachute Plant (Ceropegia sandersonii) strongly indicates that too much neem was used in the spray.
Another possibility is that you've used a shop bought ready mixed spray, or you've not got 100% cold pressed (which I strongly recommend). In both cases, you don't know what's been added to the product, and this could be what's damaged your plant.
About the Author
Over the last 20 years, Tom has successfully owned hundreds of houseplants and is always happy to share knowledge and lend his horticulture skills to those in need. He is the leading content writer for the OurHouseplants Team.
Also on Ourhouseplants.com
Credit for the Seeds of the Neem Tree photo (Azadirachta Indica) by Qniemiec