How to Spray Plants With Soapy Water – Safely!

soapy water on plant

Every plant or garden owner should learn to do to protect your plants from the numerous threats and damages of pests. I am all too familiar with the worrying sight of insects roaming around your plant and wondering how to remove these pests with minimal harm to the plant safely. Here is how to spray plants with soapy water safely.

When spraying your plants, you should use horticultural insecticidal soaps designed to target insects with minimal damage to your plants. Using these safe and specialized soaps, along with the correct method, will protect your plants from unnecessary and toxic environmental damage.

The pests you are targeting, the soap you use, and even the time of day you spray your plants all affect the plants’ health. There are safety precautions you can take to minimize the damage to your plants. Whether you even spray your plant at all or use an alternative, learning how to rid your plants of pests safely is something they will thank you for.

Safely Spraying Plants with Soapy Water

Knowing how to spray your plants with soapy water is an essential factor for any plant owner. Spraying plants with soapy water is one of the safest – if done correctly – and most effective ways to get rid of harmful pests and insects, protecting plants from the threats these small creatures pose.

However, spraying soapy water isn’t as simple as it may sound. If done incorrectly, you can cause a lot of immediate or long-term damage to your plants and soil. The soap you use, when you spray your plants, and how often you spray them are all factors that can affect your plants’ health.

Why Spray Plants with Soapy Water?

Finding pest infestations on your plants is a cause for worry. Whether you found the webs of spider mites hidden underneath leaves or just saw a number of aphids roaming around your plant, these pests need to be dealt with.

Spraying your plants with soapy water is an effective method to kill any harmful insects and pests, such as mites, aphids, thrips, whiteflies, and leafhoppers. Pest infections are never good news for a garden. Not only will pests damage infected plants, but they will spread to other nearby plants, spreading the infestation.

The type of damage done depends on the type of infestation:

  • Insects with Chewing Mouthparts – Such as grasshopper, caterpillars, and beetles, cause holes or notches in foliage and other parts of the plant, leaf skeletonizing, leaf defoliation, cutting off plants at the surface of the soil, and even consumption of the roots. Some insects also tunnel into plants, causing internal stem and leaf damage.
  • Insects with Sucking Mouthparts – Such as aphids, scales, leafhoppers, and true bugs, suck sap from the plant tissue. This feeding causes spotting or stippling foliage, leaf curling, and stunted or misshapen fruits.
  • Insects with Rasping Mouthparts – Such as thrips, scrape the surface of foliage or flowers, then suck up the spilled contents from the damaged cells.

Insects cause further damage to plants when they lay eggs, oviposit into plant tissue. Oviposition can cause a range of problems depending on where the eggs are laid. From causing death or dieback in stems and branches to misshapen or failed fruits, even if the pests are killed, their remaining eggs are just as much of a threat to plants.

Insecticidal soap is made to cause maximal damage to insects while doing minimal damage to your plants. This soap works by dehydrating insects by dissolving their exoskeletons with fatty acids. Not only is insecticidal soap effective in its job, but it is more environmentally safe and friendly than other alternatives.

What Happens to Plants with Soapy Water?

While soaps and detergents you can find around your house will kill any pests and insects plaguing your plants, but these mixtures are toxic to your plants too. A strong mixture of soapy water sprayed onto foliage can damage and disintegrate the leaves’ waxy coating, resulting in water loss and dehydration. Furthermore, the waxy layer – known as the cuticle – acts as a plant’s natural protective coat against disease and pests. The soap may also remain in the soil, making it toxic and even deadly.

On the other hand, Horticultural soaps are made to minimize any damage to the plants and environment. Of course, too much of anything is dangerous. Thus, make sure you mix and use the appropriate amount of soap, and do not spray your plants for longer than a month to avoid any damage to their leaves.

How to Spray Soapy Water Safely

There are certain precautions and further methods you can take to ensure the health and safety of your plant when spraying them with soapy water. However, your plant’s safety isn’t the only one you should worry about; for your safety, you should wear gloves when working with or spraying insecticidal soaps as they can cause skin irritations.

  • Dilute the Soap – Always dilute the insecticidal soaps per the instructions on the label. This will further corroberate the safety of your plants when you use the soap.
  • Test it First – To be safe, start by spraying a small area of a plant and wait a few days to see if it has an adverse reaction. Once you’re confident it’s safe, spray it on any other affected plants. Some plants are more sensitive than others, even a plant-safe insecticide could harm a delicate plant.
  • When to Spray – The time of day you spray the soapy water affects your plant. It is important you spray the plant at cooler times of days, opposed to when it is warm. Plants are vulnerable to dehydration in the heat, and soapy water is already dehydrating.
  • How Often – Spray the plant as soon as you see any pests taking residence, spraying the plant once a week – or every four days for serious infestations – for a month until you see an improvement. Doing it for longer runs the risk of injuring the leaf since the soap removes the natural protective oils and wax on the leaf, thus weakening the plant’s defenses against pests and diseases.
  • Be Thorough – Spray the plant thoroughly, covering every leaf carefully, including the undersides of the leaves. You want to cover as much of the plant as possible to kill as many pests on it as possible.

Only insects sprayed directly and coated with the insecticide will die; any pests that arrive afterward will be unaffected. Insecticides kill soft-bodied insects, causing no harm to their hard-covered eggs.

After Spraying Soapy Water

Firstly, once you have tested a small section of the plant with soapy water, it should be evident if it is safe to use on that specific plant. If the soapy water irritates the plant, the damage will manifest as spots of discoloration or have burn or scorch marks on the sprayed area. Although, if there are no signs of sensitivity in the plant, immediate or even after about a day of waiting, then it is safe to assume that the soapy water will not damage your plant if applied correctly.

You will know if the soapy water served its purpose by keeping an eye on the pests you are trying to kill. If you notice dead insects on the plant, a decrease in their numbers, or a disappearance of their presence altogether, then it is likely that the soapy water has done its job and killed them.

However, keep in mind that the soapy water only kills the soft-bodied pests and will not damage their eggs or larva. Thus, even if it seems like the infestation has been dealt with, there is a chance that some eggs have been left behind, and so you will have another problem when the eggs hatch.

Depending on the insect you are dealing with, their eggs could take anywhere between days to months to hatch. Therefore, it is best to research the incubation period for the particular pests you are dealing with and keep a wary eye on any affected plants for the determined time.

If an infestation re-occurs, it is likely to occur weeks or months after the original infestation – if it is caused by the hatching of dormant eggs and larva. Thus, considering the time between the influx of pests, it should be safe to repeat the process of spraying soapy water onto the plant until the insects no longer pose a threat.

Soapy Water and Other Pest Remedies

Even if you abide by all precautions and safe spraying criteria, it will all be redundant if the soapy water you use is itself a threat to the plant’s health. The most important part of safely spraying soapy water is using safe soaps and knowing how to mix them to the ideal strength and potency.

Using soaps with damaging chemicals and properties will harm your plants for obvious reasons. Spraying a solution with too much soap will also damage the plant by exposing it to higher concentrations of the soap which increases the risk of damage. Using too little soap, or diluting it too much, may hinder the soap’s effect on harmful insects and pests.

Making Your Own Soapy Water

You should never use detergents, dish soaps, hand soaps, or any common home products which contain degreasers, skin moisturizers, or synthetic chemicals. Despite ‘natural’ version labels on the soap, they are still synthetic chemicals and contain abrasive ingredients which will harm your plants. The fatty acid salts found in some soaps are made from short-chain fatty acids, which are toxic to and damage plants.

Considering the possible damages, it is always safe to use properly manufactured horticultural insecticidal soaps compared to home substitutes. Furthermore, using hard water can reduce the soap’s effectiveness, so using distilled or bottled water could be better. The actual process of making soapy water couldn’t be any simpler.

  1. Spray Bottle – Get a clean and sanitized spray bottle or sprayer for the mixture.
  2. Adding the Ingredients – Mix 1 tablespoon of your soap per quart of water.
  3. Mixing – Thoroughly mix the solution and use it immediately.

Apply the precautions and safe spraying methods mentioned above, such as testing the spray on a small plant section first to see how it will react. With the combination of spraying the plant safely and using safe soaps, you will be protecting the plant as much as possible.

Alternative Methods to Kill Pests

Soapy water and insecticides aren’t the only ways to kill pests. Other methods include:

  • Neem Oil – Use a cotton ball to wipe the oil on the leaves and suffocate the pests. Neem Oil is available on Amazon.
  • Rubbing Alcohol – Dilute with water and spray on the plant to dehydrate and kill spider mites. Here is how.

Additionally, there are more natural and indirect ways to deter and rid of pests.

  • Control Weeds – Weeds compete with your plants for nutrients and other resources. They also attract and harbor insect pests and parasites.
  • Clean Garden – Removing fallen leaves, weeds, and any other decaying matter from your garden takes away the prime breeding grounds for fungus, bugs, and diseases.
  • Insect Traps – Most garden centers carry small insect traps you can put in your garden.
  • Encourage Beneficial Insects – Insects like ladybugs are helpful in the fight against pests, eating aphids, mites, and eggs of destructive insects. Other beneficial bugs include praying mantises, lacewings, and even parasitic wasps.

Furthermore, some pests have ideal conditions, like red spider mites, which often appear in low humidity, so keeping it high should deter them. Avoiding their ideal conditions may repel them.


Using horticultural insecticides, which are designed to minimize damage to plants, along with the other precautions mentioned above, will provide further protection for your plants as you spray them with a mixture of soapy water.

However, simply spraying your plant with soapy water until the infestation appears to be gone does not guarantee that your plant is safe just yet. Bear in mind that the insect eggs could be lying in wait to hatch, posing a threat of yet another infestation.

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Anat Goldberg

Hi! My name is Anat and I have lived all my life in the countryside. I grew on a farm in Northern Italy and from an early age, I took care of the animals on the farm and the family garden. Over the years I have developed a growing passion for organic cultivation and pest control.

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