Neem oil is considered a safe and effective insecticide and fungicide for plants, but you should apply it with caution since it could burn your plants’ leaves. Additionally, certain vegetable plants are not ideal for neem oil application because it could affect their taste. Also, some plants are too fragile for neem oil and best suited for simpler pest and fungi elimination methods.
Here are 5 plants you shouldn’t use neem oil on:
- Certain herbs.
- Plants with delicate leaves.
- Leafy greens.
- Stressed plants.
- Seedlings.
Let’s take a closer look at why these plants have a low tolerance for neem oil and what you can do to provide them with other forms of protection from pests and fungi. We will also discuss using insecticidal soap, plant nettings, companion plants, and citrus rinds to keep pests away. Let’s start!
1. Certain Herbs
Neem oil is generally safe to use on herbs. In fact, you can spray neem oil on your plants right until the actual day of harvest. All you have to do is rinse neem oil off your plants, and you wouldn’t even detect a hint of it in your food.
However, certain herbs absorb odors and flavors more quickly than others. The distinct flavors and aromas these herbs are known for may be slightly altered when neem oil has been applied a few days before consumption.
Remember that neem oil coats plants’ leaves and stems to protect them from pests and fungi. Thus, it can easily penetrate the leaves and influence how it tastes and smells.
Here are some herbs that may easily absorb neem oil’s scent and taste more quickly than others:
- Sage
- Chives
- Basil
- Oregano
- Thyme
- Cilantro
- Dill
- Caraway
- Marjoram
- Parsley
- Rue.
To address pest and fungi issues, you can use insecticidal soap as an option. Insecticidal soap is generally safer and gentler on plants than most insecticides and fungicides. It can eliminate common garden pests and is not toxic to humans, animals, and beneficial insects. Insecticidal soap is also inexpensive and easy to make.
Insecticidal soap works by coating the insect’s cell membrane. When it is sprayed on plants and gets into contact with pests, it suffocates them, eventually leading to death. You should apply Insecticidal soap to your plants at least weekly to maximize its full potential.
For the soap to be effective, you must be thorough in the application and completely cover a plant’s leaves and stems.
Here is how to make insecticidal soap for your herbs:
- Pour 1 cup (240 ml) of oil (vegetable, corn, peanut, soybean will do) into a clean resealable jar.
- Add 1 tablespoon (15 ml) of liquid Castile soap.
- Mix well.
- Pour 1 cup (240 ml) of warm water into a spray bottle.
- Add 2 teaspoons (30 ml) of the soap mixture into the spray bottle.
- Mix well.
- Store the remaining soap mixture in a cool, dry place for later use.
It is best to make this insecticidal soap solution for single applications only. Discard any leftovers, or simply spray all over your plants until the spray bottle is empty. You can never use too much insecticidal soap on your plants. Remember to apply insecticidal soap in the late afternoons or early evenings to avoid leaf burn.
2. Plants With Delicate Leaves
Apply neem oil on your plants when the sun starts to go down. It can burn your plants when exposed to harsh or direct sunlight. Never apply neem oil in the mornings or at noon. Otherwise, you will end up with more issues than when you started.
Here are some of the effects of improper timing of neem oil application:
- Burnt, crispy leaf edges
- Leaf spots
- Wilting stems
- Stunted growth.
However, plants with thin, delicate leaves are more susceptible to these adverse effects, even without sunlight exposure after the neem application. They can quickly wilt and completely disintegrate if exposed to any foreign substance, even if it is organic and safe. Plants with susceptible leaves include:
- Spinach
- Arugula
- Lettuce
- Kale
- Peas.
You may want to go the insecticidal soap route again for plants with thin, delicate leaves. This option is safe against common pests and can prevent common fungal infections. Insecticidal soap solutions vary depending on your plant’s specific needs.
Here is an insecticidal soap recipe that you may want to consider for your delicate plants:
- Pour 1 liter (0.22 gallons) of warm distilled drinking water into a clean resealable jar.
- Add 1 tablespoon (15 ml) of liquid Castile soap.
- Add 1 teaspoon (5 ml) of minced garlic (to boost insecticidal properties).
- Mix well.
- Pour the amount you need into a spray bottle.
- Store the remaining mixture in a cool and dry location.
You might want to check how your sensitive plants react to this insecticidal soap solution by spraying it first on a small area of a specific plant. Observe for at least a day. If there are no adverse effects, spray the solution all over your plants’ leaves and stems. Pay extra attention to the undersides of leaves since these are favorite hiding spots for pests.
3. Leafy Greens
As a fungicide, neem oil has effects on common plant diseases. It doesn’t cure the plant of fungal infections when it has already acquired one. Rather, neem oil prevents the disease from progressing and affecting the remaining healthy parts of the plant. It can also ward off the onset of these diseases.
Common fungal diseases effectively addressed by neem oil include:
- Blight
- Powdery mildew
- Rust.
However, neem leaves an oily residue that is pretty challenging to rinse off, especially if you applied the oil just a few days before consuming the leafy greens. Hence, avoiding using neem oil on vegetable plants you intend to consume would be best. Opt for insecticidal soap instead because it doesn’t leave any residue, and you can easily wash it off.
Vegetable plants you may want to steer clear from neem oil include:
- Lettuce
- Kale
- Swiss Chard
- Cabbage.
Here is an insecticidal soap recipe that may be ideal for your leafy greens:
- Pour 1 liter (0.22 gallons) of warm distilled drinking water into a clean resealable jar.
- Add 1 tablespoon (15 ml) of liquid Castile soap.
- Add 1 teaspoon (5 ml) of apple cider vinegar (to boost fungicidal properties).
- Mix well.
- Pour the amount you need into a spray bottle.
- Store the remaining mixture in a cool and dry location.
4. Stressed Plants
When stressed, plants respond quickly to the subtlest changes in their environment. Most gardeners refer to this as “plant tantrums.” A shift in the watering schedule may lead to wilted leaves. Repotting an overgrown plant may bring about yellow leaves. A good spritzing of neem oil might suddenly instigate leaf drop.
To avoid plant tantrums in stressed plants and protect them from pests and fungi, it would be best to go for other defense modes. Leaving them without any protection should not be an option. At this stage, their defenses are low, and they’re more vulnerable to pest infestations and infections.
A great way to protect your stressed plants is with citrus rinds. The rinds of citrus fruits are excellent pest repellents. This option is a practical way to protect your stressed plants and give yourself a boost of vitamin C, too! All you have to do is scatter citrus peels around your plants, and you can rest assured that pests will stay away from them.
Citrus fruits contain D-Limonene, a natural insecticide that is effective and entirely safe for plants. Your stressed plants will have a barrier of protection from pests, especially during this crucial phase. In addition, pesky pests hate citrus smells so they will balk at the sight and smell of rinds scattered on your garden floor.
Here are some tips on how to use citrus rinds as pest repellents:
- Chop up the rinds so you can scatter more of them near more of your plants.
- Use only fresh rinds since these can retain the pungent, citrusy scent longer.
- Replenish your rinds every few days as soon as you notice them drying up.
- Make sure there is no fruit flesh sticking to the rinds because these may attract ants and other unwanted insects to your garden.
Here are some citrus fruits you can stock up on:
- Grapefruits
- Oranges
- Lemons
- Lime
- Clementine
5. Seedlings
Plants are most vulnerable when they are in the seedling phase. They haven’t established a robust defense system against common pests and fungi, which mature plants may handle more easily. Additionally, insects like caterpillars and thrips prefer preying on seedlings because of the softer, juicier plant matter.
Wait until the seedlings are at least two months old before exposing them to neem oil. Neem could burn their delicate foliage quickly. At this sensitive stage of development, opt for safer ways to keep pests at bay.
Here are some options to consider for your seedlings:
Companion Planting
Surround your seedlings with plants that naturally deter pests. These will act as natural shields against pests so they can focus more on growing bigger and stronger. Companion plants are also helpful, giving you more to gain in the long run.
Here are some of the most reliable companion plants for seedlings:
- Coriander
- Fennel
- Catnip
- Dill
- Nasturtiums
- Marigolds.
Plant Nettings
Plant nettings are a simple, practical, and inexpensive way to keep your seedlings safe. Invest in nettings with durable mesh covers that you can count on to keep many types of pests away, including the tiniest ones like aphids and fungus gnats. Install your netting correctly to protect your seedlings from extreme weather conditions.
If you want to learn more about installing nettings to keep pests away from your plants, check out my other article. I’ll discuss plant nettings, how they can protect your plants, and how you should use them in your garden: Does Netting Really Stop Japanese Beetles?
When your seedlings are stronger and bigger, you can include them in your usual neem oil spray routine. Neem works by coating the insect’s body with oil, making it more difficult to breathe. Neem also prevents eggs and larvae from progressing to the next stage of development. It kills pests by interfering with their abilities to feed and reproduce.
These are some of the pests neem oil can eliminate:
- aphids
- Thrips
- Caterpillars
- Beetle larvae
- Lace bugs
- Leafhoppers
- Leafminers
- Mealybugs
- Whiteflies.
What’s good about neem oil is that it does not affect beneficial insects, as long as it is not sprayed directly at them. Beneficial insects include pollinators and those that feed on pests. Here are some of them:
- Bees
- Butterflies
- Ladybugs
- Parasitic wasps
- Earthworms
- Spiders.
Key Takeaways
Remember that although it is a favorite among gardeners, certain plants will be at a higher risk of deterioration if exposed to neem oil. Some of them are seedlings, stressed plants, certain herbs, and leafy vegetables.
This potent insecticide must coat the entire plant to work its charm. It would be best to test a small area of an infected plant first to see how it would react. You can spray the entire plant with neem oil if there are no observable adverse effects.
