Spraying Cannabis Plants: Quick, Easy & Effective

Not everyone realizes that spraying marijuana leaves is a highly effective way to overcome short-term nutrient deficiencies. You can also spray your plants with insecticides to quickly destroy pests that threaten to ruin your crop.

However, there’s an art to spraying cannabis, and you can’t rely on it for positive long-term results when feeding your plants

This article explains what I mean by “spraying,” outlines when you should and shouldn’t consider it, discusses the issue of timing, and concludes with some quick tips.

What Is Foliar Spraying?

The term “foliar spraying” relates to the process of spraying water laden with nutrients onto the leaves of your marijuana plants from a spray bottle. A lot of novice growers seem to focus on ensuring their plants’ root systems absorb nutrients. Such individuals may not realize that plants also take in nutrients through the stomata (small openings) in their leaves.


Moreover, it can be a useful practice when your marijuana plants are suffering from a nutrient deficiency. According to researchers at Michigan State University, a plant’s leaves can absorb up to 95% of nutrients. One downside is that the data is rather old. Another is that only a small amount of spray gets into the plant via the leaves. On the plus side, most foliar sprays drip off the leaves quickly, which means the nutrients end up in the roots anyway!

Technically speaking, foliar “feeding” relates to spraying your marijuana plants with nutrients. Meanwhile, foliar “spraying” is mainly for applying insecticides to deal with pest infestations.

Now, let’s learn more about the dos and don’ts of spraying your cannabis plants.

When Is It a Good Idea to Foliar Spray Your Marijuana Plants?

The main reason why you should look towards foliar feeding is to quickly reverse nutrient deficiency in your crop. Your plants will absorb nutrients more quickly through the leaves than through the soil.

While they will only get a relatively small amount, the speed of absorption could tide your plants over until their roots begin taking in the rest of the nutrients. Remember, the leaves can absorb all but 5% of the nutrients they take in. Many growers say they can see the results in less than 48 hours.

Combating pest infestations is another occasion when foliar spraying makes sense. Applying a spray containing insecticidal soap or neem oil and potassium soap can eliminate harmful pests like whiteflies and red spider mites. You can even create natural pesticides using household ingredients like cinnamon oil and cayenne pepper to vanquish pests and eliminate problems such as powdery mildew and mold.

Some growers also like to apply foliar sprays as preventative measures. A neem oil solution sprayed onto leaves can ensure pests don’t get busy with your crop. Meanwhile, a CalMag solution might be just the ticket if you aim to add micronutrients that your marijuana plants may struggle to absorb from the growing medium.

Here’s When to Avoid Spraying Your Cannabis Plants

It’s important to steer clear of foliar spraying during the flowering period. Even natural insecticides, such as neem oil, can ruin the taste of your buds when you apply it too late in the growing cycle. Furthermore, you risk the formation of mold because of excessive moisture creation.

If you want to spray your plants to kill pests, please ensure you only spray the fan leaves and not the flowers! You will make things easier for yourself by using a regular handheld misting bottle, which ensures it’s easier to hit the target. Larger containers are primarily useful if you have a lot of plants.

You should also remember that it is a short-term solution. Your plants receive a limited nutrient dose. It can serve as a boost, but relying on absorption through the leaves alone will ensure your plants fall way short of their nutrient requirements.

Timing Is Everything When Spraying Your Crop

If you grow marijuana indoors like most people, getting the timing right is relatively easy. After all, you’re in control of the grow room’s climate. In this situation, you can foliar feed when the lights are on, but please ensure the plants are not beneath them at the time. Instead, take your plants out of the grow room/tent when feeding them via spray.


After spraying, wait until the excess water dries up. Now, you can return them to their rightful place, safe in the knowledge that they won’t burn up.

You can simplify matters by spraying in the morning before the lights come on. Alternatively, feed in the evening before the growing lights are due to go off. In both cases, the grow room temperature should be at the right level.

What About Outdoors?

Things get a little more complicated if you’re one of the rare individuals who grows marijuana outdoors. If you live in an area with a typical outdoor climate, spraying when the sun is about to rise or set should serve you well.

However, if you live in a humid climate, spraying in the morning is by far your best bet. If possible, complete the process about 60 minutes before sunlight hits your plants. In this situation, the water soaks in, and you don’t have to worry about the liquid staying on the leaves for too long during the night. Remember, excessive moisture exposure can lead to mold and mildew forming.

For growers living in hot climates, spray the leaves in the evening as the sun starts to set. This enables the water to soak in, and you don’t need to worry about it lingering on the leaves at night. Spraying in the morning may prove ineffective as the water could dry up long before it gets absorbed.

Here Are Some Quick Cannabis Spraying Tips

Follow these tips to get the best results when spraying marijuana plants:

  • Don’t spray when the temperature is too hot or cold
  • Avoid completing the process during inclement weather; rain and wind can wash away the solution before it has any effect
  • Always remember to spray the underside of the leaves
  • Read the instructions on the nutrient solution you use; whatever the recommendation is, use half at first if the product doesn’t specify its use in a foliar spray
  • Never spray your marijuana plants in direct sunlight
  • Test the spray on a single leaf to see the results before applying it to your entire crop
  • Don’t spray your plants once they’re in the flowering stage

Foliar Feeding Is a Useful Short-Term Solution for Hungry Marijuana Plants

If your plants are showing signs of a nutrient deficiency, you can implement foliar feeding as a quick way to get things back on track. The leaves of your marijuana plants can absorb nutrients at a staggering rate, so spraying them can save you time as you search for a longer-term solution. Spraying your plants can also get rid of pest infestations before they cause major damage.

Still, you have to understand that you should only use foliar feeding as a supplement. Your marijuana plants will grow bigger and healthier when their roots absorb the nutrients they need.

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