The neem tree (Azadirachta indica) is an incredibly versatile plant with many uses. In India it is known as “the village pharmacy”–over 75% of Ayurvedic remedies contain some form of neem!–and lately the tree has also been called “the world’s most researched tree.” But even though neem has been used traditionally for several thousand years it is still relatively unknown in the western world.

Apart from the seemingly all powerful neem oil–pressed or extracted from the seeds–there are a whole range of other neem products: neem capsules, neem soap, neem tea, neem bark powder… Most people have heard about neem oil only and they don’t know much about it. For neem to live up to its reputation you need to use the right neem product the right way, at the right time for the right purpose!

In this article I will look at the most common use of the oil: as an insect spray in the garden.

Neem oil is an absolutely wonderful alternative to chemical insecticides because it is totally non toxic to humans. If used correctly it works wonders and it only affects the bad bugs while leaving the good bugs unharmed.

The keywords in the above sentence are “if used correctly.” Here are seven things you should understand about neem oil before you use it in the garden.

  1. Neem oil is NOT an instant knock down insecticide. Neem does not kill insects or grubs instantly! It acts as a feeding repellent and it also interrupts their breeding cycle. Neem is similar to insect hormones. When insects take up the neem ingredients they “forget” to eat, to mate, or they stop laying eggs. Some forget that they can fly. If eggs are produced they don’t hatch, or the larvae don’t moult. Don’t conclude neem doesn’t work just because it doesn’t kill everything instantly. Neem oil needs to be used regularly. Spray it once a week to once a fortnight and it WILL protect your garden from sucking and chewing bugs.
  2. Neem CAN kill honey bees. Neem is not toxic to honey bees or other beneficial insects but it can certainly kill them! Any oil you spray can coat insects and suffocate them. In that respect neem oil makes no difference between good and bad bugs: coat them with oil and they suffocate. To protect beneficial insects, only spray neem in the very early morning or late afternoon, when insects are least active. Once the oil has dried it only harms the bad bugs.
  3. Neem CAN harm your plants. If a little bit helps, then more will help better. Right? Wrong! Any oil spray can burn plants. If you spray during the day it burns better. Again, use neem spray early in the morning or late in the afternoon, so it can dry before the sun hits it. Some plants are so sensitive, they don’t need the sun to suffer. Having their delicate leaves coated with too much oil is bad enough. Stick to the instructions! Use the lowest concentration and do a little test application first. Neem oil is strong stuff. A little goes a long way.
  4. Neem CAN harm aquatic organisms. This aspect is rarely mentioned. Research studies showed that neem ingredients can hurt many aquatic organisms, including fish and tadpoles. Luckily it takes more than just traces to do damage. Spraying near ponds is generally safe, but do not spray neem directly into the water.
  5. Neem oil is NOT registered as an insecticide. In most countries neem oil is not registered as an insecticide or insect repellent. So the sellers are not allowed to call it that or to mention that it kills or deters insects. If you try to buy neem at the local hardware store, don’t look in the aisle with the poisons. Rather look for leaf polish… Seriously, that’s what one manufacturer sells it as. The easiest way to find it? Ask for it. But beware…
  6. All neem oils are NOT made equal. Many people hear about neem oil, go to the hardware store or garden center and buy some “neem plant spray” or “neem based insecticide” or other ready to use mixture of who knows what. Some of those bottles contain nasty chemicals with a bit of token neem. Few contain raw neem oil–the most potent neem oil–but rather a clarified hydrophobic extract. Those extracts are not as powerful as the raw or crude neem oil. The best neem oil to buy is raw, cold pressed, organic oil with a high Azadirachtin content. Azadirachtin is the main insecticidal ingredient and most sellers of good neem oil advertise the high Azadirachtin content. By the way, you are unlikely to find the raw oil at your local hardware store. Try health food stores instead!
  7. Neem oil STINKS! The descriptions of the smell vary. Rancid peanut butter, rancid garlic, rancid burnt onions… do you detect a theme here? How about garlicky peanut butter with some rotten eggs thrown in?

I’d say, just get some and come up with your own description. And get used to it. Because the stuff really works!