Can neem oil kill plants, is this a query a lot of DIY gardening enthusiasts ask about? It is not uncommon for someone to use pure organic neem oil on plants for pest control and kill the plant in question.Neem Oil Kill Plants

This article will explain how and when this oil kills plants. Carry reading, as we will also discuss how to avoid killing plants while using neem oil.

Can Neem Oil Kill Plants When Used as an Insecticide?

Now, neem oil doesn’t kill plants when used as an insecticide. However, it can leave dangerous side effects on them when misused. The oil can cause the leaves to burn, and it can also block the respiration of the cell, and it can also kill the seedlings of the plant.

Neem oil cannot kill plants unless used without dilution or on the wrong plants. It can just cause severe damage to plant parts like leaves and stem sheaths. This usually happens when this oil is misused or on the wrong plants.

– It Can Burn Leaves

We all know oil heats up efficiently when exposed to light or high temperatures. If neem oil is applied in a thick, undiluted layer over the plant, it will heat up and cause burns, and so the leaves will get damaged in the longer run. The wider the oil layer, the more severe will be the burns caused by it.

Like the rubber plant, plants with thick leaves could resist; on the other hand, they would get burned better than those with thin leaves. Plant parts that get burned turn black in color and might necrose in the center. These burns are irreversible and will not get better with time or care. If a large part of a leaf sustains burns, then these leaves might die and fall off the plant.

– It Can Block Respiration

Applying pure neem oil over the leaves and plant parts can significantly decrease respiration in a plant. Undiluted oil particles are pretty large and clog tiny pores called stomatam and this would hinder the growth of the leaves but not the whole plant.

These pores are responsible for carrying out gaseous exchange for the plant. As a result, the plant is not able to carry out photosynthesis or deal with stressful conditions properly, and this is one of the Neem oil side effects.

– It Kills Seedlings

Applying neem oil to germinating seeds and seedlings will kill them. Seeds require high temperatures, high humidity levels, and bright light to grow into seedlings. Using this oil on the seeds in such conditions will heat them to the point of causing burns. Seedlings and plants younger than two months are also too sensitive and will get oil burns quickly.Applying Oil to Germinating Seeds

What Are the Factors That Lead Neem Oil to Kill Plants?

The factors that help neem oil kill plants are high daily temperatures, direct and bright sunlight, and frequent application. Neem oil works best diluted in a large volume of water. Applying just oil to the plant will decrease its respiration.

– Very High Temperature

Neem oil application on plants when the temperatures are high will cause severe heat burns to the leaves. Like most vegetable oils, it has a low boiling point and quickly gets hot.

In this case, you will see how the leaves obviously cannot withstand the hot oil and end up frying because the effect of the oil is not compromising the heat of the weather. In addition to this, you should also be mindful that the oil that has not been appropriately diluted will get heated faster than undiluted oil.

This problem is encountered during the hot summer months from May to August or September when the weather gets hotter. Indoor plants are at risk even during winter if you like to keep your indoor temperature very high. In addition, when plants are kept near the fireplace or the radiator are also at risk.

– Harsh Direct Light

Light carries energy and heat that causes oil to burn and kill plants. Leaves of fruit trees and plants growing outdoors under very bright light are most at risk. This is why we avoid using oil during daylight when the sun is out, especially from noon till the afternoon.

Plants kept inside the house are not 100 percent safe, either. Sunlight coming from a south-facing window is the harshest and will help the oil in killing plant leaves. The sun is directly overhead, and the temperatures are too high at this time of the day, and with this.

Light coming from the eastern and the western windows is intense only during the morning and evening, respectively. The northern window is the only one that receives indirect sunlight, which is not strong enough to help oil kill a plant, but if this condition fails, it will cause a different issue for the plant.

– Wrong Timing

Timing is everything when it comes to applying anything to the plants. No matter how diluted it is, noon is the worst time to use oil on plants. This point is particularly pertinent for outdoor plants and vegetable gardens.Leaves of Fruit Trees

For oils, the best time for a foliar spray is either early on at dawn or late at dusk when you are using it. You can easily avoid sunlight and keep the oil from burning leaves, but when applied at the wrong time, the thin leaves may be placed at a higher risk. These are also when most beneficial insects leave the plant, and you can avoid killing them accidentally.

– Applying Oil Too Frequently

Even if the oil has been emulsified and diluted with water, its particles are too large to pass through the plant’s pores. They end up clogging these pores and stopping the interchange of gases between the plant and the atmosphere.

A single application of diluted neem oil insecticide will not clog many pores. This oil stays on the plant’s surface for about seven days before it breaks down. After seven days, a second foliar application can be given if needed.

Applying the oil again and again too soon will cause more and more plant pores to clog up, and this can suppress its growth and cause the plant to weaken in the longer run. As a result, the plant’s overall respiration will decrease significantly, which might cause it to die, if it happens on a frequent basis.

– Incorrectly Diluted Oil

A recipe must be followed when using a neem oil spray to kill pests or treat fungal diseases. Only one tablespoon of this oil in a gallon of water is safe for plant consumption. Some gardener may go ahead and dilute their oil with only a tiny quantity of water, thinking it will make the spray more potent.

What actually happens is that they end up killing their plant from both burns and respiration blockage. This can also be the case when you are using a strong amount of pure neem oil that has a direct impact on the plant cells.

Even when pouring this oil solution over the soil, dilution is non-negotiable. Otherwise, the oil will stay in the soil longer and might kill beneficial bugs. It also clogs the tiny pores present on the surface of plant roots.

Moreover, the roots will have difficulty breathing and taking in water and nutrients. The poor plant is at risk of dying from suffocation and starvation, and this way, it can cause them to die.

How to Use Neem Oil Without Killing Plants?

Use neem oil without killing plants by emulsifying and diluting it with the correct quantity of water. Plants that are at risk should not be sprayed upon at all. Wait till dawn or dusk to spray the plants, and constantly water them before the spray.

Neem oil is mixed for plants after being emulsified by liquid soap or silica powder. Mix just one tablespoon of oil with one tablespoon of soap or powder for emulsification in one cup of water. When the oil droplets disappear in water, add this mixture to one gallon of water for dilution, and that is the right way how to mix neem oil for plants.

– Dilute With Water

Neem oil must be diluted with a lot of water before it can be used safely on plants. One tablespoon per gallon of water is the most effective dilution ratio. You should also be mindful about the oil quantity being too less, as this mixture will eliminate houseplant pests within a few applications only.Neem Oil Spray to Kill Pests

You would see how the oil works on a plant for seven to 14 days after application. Even if diluted properly, it will carry its insecticidal and fungicidal action for at least seven days. That is why you must never spray it more than once or twice weekly, and risk the health.

You can spray neem oil over the plants’ soil instead of the leaves. This is called a soil drench, mixed like a leaf spray. Spreading oil directly over the soil helps eliminate the pests, such as fungus gnats and root aphids. You can get a pressed form of neem oil called neem cake and use it as a soil fertilizer.

– Soak the Plant in Water

If it is time for the plant to be watered, then carry that out before spraying it with neem solution. This is important when pouring water over the soil for a proper drench. If oil is run first, it will block the roots and stop them from absorbing moisture.Soaking Plant in Water

Ultimately, the plant must wait for the neem to disintegrate before reenter the water. This might take as much as seven days, during which the plant will remain dehydrated, so make sure that you also keep on giving it the right care needs.

– Avoid Sunlight

Stop spraying the plant during the daytime if you don’t want to kill it. Wake up early before sunrise to pour a small amount on the plants under infestation. Make sure that you would spray late in the evening so the oil can kill bugs without getting heated by sunlight.

For indoor kept plants, you can move them away from the direct light source for a day or two. If you are wondering is neem oil safe for humans, you should not worry because it is safe for external human use on skin and hair. It is also suitable for dental health and oral hygiene.

– Avoid Plants With Thin Leaves

Plants with thin leaves get killed or burnt easily when we apply neem oil. These plants can be ornamental, like the spider, or vegetables like lettuce and cabbage. An adequately diluted oil solution is not recommended because these plants are too sensitive. Moreover, most of these vegetables are grown outdoors, so there is the added risk of sunburn.

Even plants that are usually not killed by neem are at risk when stressed, such as transplanted plants. It is best to avoid neem and other oils on them until they get adjusted to their new home.

If you are unsure whether a plant will tolerate neem, do a patch test on one leaf first, and you will be taking the right measures for the plant’s health. If it does not get burnt, wilted, or die, proceed with the rest of the plant.

– Avoid Herbs

Herbs cannot tolerate being sprayed with neem or any other essential oils. Their leaves are just too sensitive to handle the compounds present in neem.

In such a case, what happens is that their leaves will burn quickly, or they might suffer from stunted growth after such an application. If the herb plants are already stressed, neem might even kill them.

Many of us who own a kitchen garden love growing Cilantro, Thyme, Oregano, and Parsley at home. These plants are easily susceptible to infestations by aphids, spider mites, mealybugs, etc. Instead of going for oils, try out homemade vinegar or garlic sprays on these plants.


Neem oil can kill plants only when used irresponsibly and on the wrong plants.

  • The oil gets heated under sunlight and during summer and burns the plants.
  • The oil will clog the plant’s stomata and suffocate if undiluted or used too frequently.
  • Always mix this oil with water and soap in the correct ratio to eliminate garden pests.
  • Neem oil kills seeds and seedlings with a single application and should not be used.

In conclusion, following the safety precautions explained in this article can protect your plants from dying after neem oil is applied to them.

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