What is and how to use Neem oil

Published Jul 28, 2019 09:27 a.m. ET
iStock / Mukesh Kumar

When it comes to growing cannabis, there are many different methods to choose from, but those who prefer an organic crop need to equip themselves with the right products. A lot of synthetic nutrients and fertilizers claim to be all-natural, but unfortunately, the majority are far from it. There are genuine organic alternatives such as Diatomaceous Earth that can help to rid a crop of problems but aren’t nearly as effective as other alternatives on the market today; like Neem oil. Cannabis research is showing a massive difference in the adverse effects that can come from chemical-laden products. So even if your goal isn’t to stay 100% organic, it’s still a good idea to learn the tips and tricks of the trade that will help you to naturally protect and cultivate a plentiful crop. So, whether you like to smoke weed everyday or just enjoy growing the plants for their beauty, here is everything that you need to know about Neem oil.

What is Neem oil?

Neem oil is one of the few pesticides on the market today, that is not absorbed by the marijuana plant.

It is harvested from the Neem tree, which naturally produces a thick sap and grows mainly on Indian subcontinent. Though many people believe it is the sap that makes up this oil, it is actually made from processing the leaves and fruit into a liquid.

Can Neem oil cause cannabinoid hyperemesis syndrome?

Cannabinoid hyperemesis syndrome is a term that is used to describe marijuana consumers who report adverse effects after smoking, which may or may not include dramatic temperature fluctuations, vomiting and intense nausea. As of now, cannabis researchers have not been able to confirm any link between the use of neem oil and the symptoms of cannabinoid hyperemesis syndrome.

What is Neem poisoning?

If you have heard about neem poisoning, then you might also be concerned for the health and safety of those who consume any plants that this pesticide is applied to. However, neem poisoning occurs from ingesting large quantities of neem oil directly, not from smoking it. Since this oil is not absorbed by cannabis plants, there is no reason to worry about your product. The only safety guideline recommended is to refrain from using this treatment for the final 3-4 weeks before harvest.

Neem oil for infestations

Though there are many more reasons that organic growers use Neem oil on the cannabis plant, treating for infestations is one of those reasons, below are some of the most common insect infestations neem oil will help to rid:

1. Leaf miner infestations
Leaf miners are unable to feast through or even get a grip on Neem oil covered leaves.


2. Aphids
These irritating bugs will die almost instantly after an application of Neem oil, as it stops them from breathing and the few that survive can no longer munch on the marijuana plants’ leaves.

3. Fungus gnats
Gnats can be challenging to treat with old school methods like dish soap and water, but since they thrive by reproducing in contaminated soils, the best way to halt an infestation as soon as its stats is by dousing the surrounding dirt with Neem oil.

4. Spider mites
After the removal of as many webs as possible, spraying your marijuana plants will kill an infestation and encourage brand new growth.

5. Nematodes
As the Neem oil makes its way through the soil, through regular watering, it will cleanse by destroying harmful nematodes and turning them into easy to absorb nutrients.

How to mix and use Neem oil

You will need:

• A bottle of neem oil
• Surfactant
• one mister bottle
• and warm water


  1. Add one teaspoon of neem oil for every one liter of water. Do not mix any more than you need for one application, as the fat will solidify as it cools which can plug the spray bottle, and it will no longer be able to stick to the leaves, as such it is essential to make only one batch that can be used up in a single treatment.
  2. Shake the mister bottle and allow the mixture enough time to set, usually 1-3 minutes is excellent.
  3. Add 3-4 drops of surfactant, then give one more rigorous shake of the bottle. Now you are set to make your very first neem oil application. (Surfactant helps the oil stick to the leaves, without it, the mixture will not be nearly as effective)
  4. Evenly coat all the cannabis plant leaves, starting from the top and slowly work your way down. It helps if the plant is in a pot so it can be spun, as it needs a spray from every direction for a full coating.
  5. Once the leaves are treated, gently moisten the top layer of the growing medium for an added layer of protection.
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