Imagine your cannabis plant is suffering from a nutrient deficiency because of a lockout in the root zone. While you try to fix the issue in the substrate, your plant is starving already. In this case, you can help your plant by foliar feeding it the nutrient solution.
But this isn’t the only way foliar feeding can help your cannabis plant. It can help your plant fight diseases, pests, fungal infections, and a lot more. In this article, learn everything you need to know about foliar-feeding cannabis plants, including its benefits, when and how to use it, and some extra tips.
Typically, you feed nutrients to your plant via the root drench method, where you administer the nutrient solution to the roots via the substrate. In foliar feeding, instead of drenching the substrate, you administer the nutrients directly to the leaves of your cannabis plant.
Note that foliar feeding is not a substitute for root drench — it's only a way to give your plants a nutrient boost in specific cases, like nutrient deficiencies. This is because the stomata of the leaves can quickly absorb nutrients, helping the plants recover from the deficiency.
Below are some benefits and drawbacks of foliar-feeding cannabis.
Foliar feeding is easy and that’s not even its biggest benefit. Here are some of the top benefits of foliar feeding of cannabis plants.
Nutrient deficiencies are common in cannabis plants for various reasons — wrong pH level in the substrate, nutrient lockout, incorrectly balanced solution, etc. — and in such cases, you must fix the problem quickly.
Here, foliar feeding comes into play as it allows you to feed the plant quickly via the leaves’ stomata, i.e., pores on the epidermis of the leaves. These pores are usually responsible for gas exchange (of CO2 and oxygen), but when they are open, they can also consume nutrients.
And these spores consume nutrients at a much faster pace than roots, making foliar feeding a terrific way to give your cannabis plants a nutrient boost.
Foliar feeding does not only come in handy when the plant is suffering from nutrient deficiency but also when it is suffering from a nutrient lockout. In the latter scenario, there may be salt or mineral buildup in the substrate that may be hampering nutrient uptake.
With foliar feeding, you can bypass the lockout by giving your plants the nutrients they need without any delay. In the meanwhile, you can fix the nutrient lockout before resuming the usual feeding routine.
When you feed nutrients to your cannabis plant via foliar feeding, it leads to a few positive side effects for the plant. One of them is that the roots give off more carbohydrates than usual into the substrate, which aids the microorganisms that further help with nutrient uptake.
Apart from feeding the plant, foliar sprays can come in handy for treating and preventing various fungi and pests like powdery mildew, mites, etc. These foliar sprays may not contain any nutrients per se but contain compounds that kill or deter pests and fungal spores.
One of the most popular foliar sprays for pests and fungi is neem oil, which is completely natural and quite effective. Another popular pesticide foliar spray is made with potassium soap, or other ingredients like nettle, cinnamon oil, cayenne pepper, etc.
Since foliar sprays tend to be fast-acting, many growers use this method to feed grow boosters or stimulants to their plants. There are various such products available in the market, and you can even make such sprays at home with a few basic ingredients like aloe vera leaves and water.
While foliar feeding is a terrific solution to various problems and can act as an alternative to your plant’s regular feeding routine, it does have a few downsides. These downsides prevent foliar feeding from becoming a total alternative to root drench, which is why it is only recommended to use foliar feeding in specific scenarios.
Here are some of the downsides of foliar feeding for cannabis plants.
Foliar sprays that contain nutrients are strong, so when you completely rely on foliar feeding for the nourishment of your plant, it can result in phytotoxicity or leaf burn, where the water evaporates quickly and nutrients build up on and within the leaves.
Over time, leaf burns can cause various problems, including stunted growth and compromised yields.
At the same time, foliar feeding cannot provide all the nutrients your plant needs — the sprays have to be slightly diluted compared to root drenches and the nutrients don’t have the liberty to be suspended in the substrate until the roots absorb them.
This is another reason why foliar feeding is only beneficial as an aid, not as a replacement for root drench feeding.
Again, because of being diluted, you need to foliar feed your plant more frequently to meet its nutrient demands. This is impractical because it can consume a lot of your time and even cost you more money.
Foliar feeding can only benefit your cannabis plant when you use it at the right time; otherwise, it may not be so effective, and in worst-case scenarios, you risk nutrient burn or contaminated buds on your cannabis plants.
This is why it is crucial to know the right time to foliar feed cannabis plants and you must do it properly. Here are some pointers to help you out.
Foliar feeding works wonders in giving your cannabis plant a nutrient boost and deterring some pests or insects. However, you must only foliar feed your plant during its vegetative stage. You can also foliar feed the plant in the first few weeks of flowering, but remember to stop as soon as you see flowers.
This is because foliar feeds contain nutrients that can contaminate the flowers. If you foliar feed flowering cannabis, the buds can end up tasting or smelling weird, which is something you don't want.
On the other hand, when you notice any signs of nutrient deficiencies in a vegetative cannabis plant, you should consider giving your plants a foliar treatment. As mentioned earlier, your plant can intake cannabis a lot faster, which helps them recover better from the deficiency.
At the same time, you should work to fix the nutrient deficiency by rebalancing the pH of the substrate, checking the nutrient solution, flushing the plant, etc., and once the problem is resolved, you can resume the regular feeding cycle.
If your plant is at a higher risk of pest or fungal infection, especially in humid conditions, you should regularly use foliar feed pesticides or fungicides to prevent such problems. You can also use foliar pesticides or insecticides to deal with pest infestations or fungal infections.
The stomata on your cannabis plants are not always open and ready to consume nutrients — the window for this is quite narrow. During the day, the stomata pores are dilated and only open up fully during the early evening and stay open for around 20 minutes.
At the same time, you don’t want to foliar feed your cannabis plants during the day or when the grow lights are on. When the lights are on, the nutrient droplets can magnify the light, causing the plants to burn. Plus, intense light can also degrade various nutrients.
So, if you are growing cannabis outdoors, it is recommended that you only foliar feed your cannabis plants once the sun has set but not too late into the evening. And for indoor cannabis plants, you can foliar feed them once you turn off the grow lights.
When the temperatures are too high, usually during the afternoon, the stomata pores are completely closed. They can also close up if your grow room temperatures rise a little too much. This will make your foliar sprays a lot less effective.
On the flip side, foliar feeding when the temperatures are too low can lead to fungal growth because the water cannot evaporate on time. When the temperatures are ideal, the water can evaporate at the right pace, preventing the risk of fungal growth.
As mentioned earlier, foliar feed contains nutrients that don’t have the luxury of time for absorption — they must be absorbed properly within a small window when the pores are open. Otherwise, they may accumulate on the leaves and cause nutrient burns.
So, you need to avoid overfeeding your cannabis plants — which is an easy mistake many new growers make.
If you are using the same nutrient solution that you used for the root drench, you need to dilute the solution and only use 25% of the feeding. You can make the solution more concentrated if required, but be careful and keep an eye out for nutrient burns on your plant.
And while you should follow your regular feeding routine, avoid foliar feeding your cannabis plant more than once a day.
When foliar feeding, you are obviously going to spray the canopy — uppersides of the leaves — but do not forget the undersides. More stomata pores are located on the underside of the leaves, so your plant can consume more nutrients.
Additionally, various pests like spider mites like to hide on the underside of the leaves. Spraying foliar to deter such pests is only effective when you eliminate them in their hiding spots, i.e., the underside of the leaves.
Surfactants, also known as wetters, help a liquid spread better. Surfactants allow your foliar spray to cover the plant more uniformly, increasing its retention and reducing wastage. We recommend using surfactants like insecticidal soap in your foliar spray.
Insecticidal soaps not only act as surfactants but can also kill pests on contact by puncturing their exoskeletons and dehydrating them. You can use this soap to deal with mealybugs, aphids, spider mites, aphids, and whiteflies.
Before you start spraying your entire garden with foliar feed, first do a patch test on a part of the plant. Wait for a day and check for any damage. If the patch is healthy, you can then foliar feed the entire plant.
When foliar feeding your cannabis plants, you should use a sprayer that produces a fine mist, not big droplets of water. When misting, there are two types of foliar sprays you can use — hand sprayer and pump sprayer.
Hand-sprayer is ideal for small cannabis gardens as it is easy to use and can hold up to a liter of the nutrient solution. Hand sprayers are also effective at more precise sprays, where you only want to spray a specific part of the plant.
On the other hand, a pump sprayer comes with a spray wand and can hold a lot more nutrient solution. This sprayer allows you to completely cover the plant easily, so you can use this if you want to foliar feed many cannabis plants. This is the same spray farmers use.
Whichever sprayer you use, ensure that it can spray medium-sized droplets that cover a wide area — the droplets should be between 100 to 175 microns. Generally, many high-quality sprays allow you to control the droplet size, so choose those. They may be a little expensive but are worth it.
When using foliar sprays, you should always be careful. While most foliar solutions are safe, some of them may contain substances that can be toxic or unhealthy for you, so you don’t want to spray them on yourself.
Follow the manufacturer’s recommendation, and use gloves, eye gear, and a face mask when foliar feeding your cannabis plants. And never ever spray your cannabis buds with any foliar sprays.
Apart from your regular root drench solution, you can use various other solutions as foliar feeds — some of these are antifungal and anti-pests and others work as boosters and supplements. Here are some of the most popular foliar sprays you should know about.
Perhaps the most popular foliar feed is neem oil, which is also one of the most effective ways of treating fungal infections and pest problems. This is one foliar feed that every cannabis grower must have in his arsenal.
Neem oil is 100% organic and safe to use on vegetative cannabis plants and can help fight fungal infections, aphids, white flies, thrips, spider mites, and various other pests. This is why many growers use neem oil as a preventative measure against pests and fungi.
If you want to use neem oil, you can use it to kill fungi and insects when you spot them, and as a preventative measure, you can use them once every couple of weeks.
Another effective remedy to pests is potassium soap, which can kill various common pests on contact. Plus, it is completely natural, non-toxic, and safe for the cannabis plant. Most potassium soap solutions are prepared by adding potassium soap to water in a 2% concentration, but this may vary, depending on the manufacturer.
You can also use potassium soap with neem oil to make a deadly combo for the pests that are trying to hurt your cannabis plant. Spray potassium soap on your plant to eliminate the pests quickly and follow it up with neem oil the next day to eliminate any residual pests and prevent them.
Another common organic foliar spray for cannabis is aloe vera juice — it is multi-purpose and helps your cannabis plants in various ways.
The biggest benefit is that it is rich in various micronutrients like calcium, magnesium, manganese, and zinc, along with other compounds like enzymes and amino acids. If you notice any signs of micronutrient deficiency, you should ideally reach out for aloe vera juice.
Additionally, aloe vera juice also protects your cannabis plants against other environmental stressors as it contains various compounds like acemannan, which is antiviral, antifungal, and antibacterial. Other beneficial compounds that aloe vera juice contains include aloe and saponins.
Making aloe vera foliar spray is quite easy — mix two teaspoons of aloe vera gel with 4.5 liters of water and shark well.
Humic acid acts as a chelator, which helps combine organic compounds with minerals so they can be easily absorbed by the plant. These compounds essentially turn insoluble minerals more soluble so they can be consumed by plants.
You can purchase humic acids in either liquid or dry forms, both of which are easy to mix in water. Just follow the manufacturer’s recommendations and you'll be good to go.
On the other hand, fulvic acid contains various trace minerals like iron, copper, manganese, and zinc. It also improves the nutrient uptake in cannabis plants while boosting the plant’s natural resistance to various stress factors.
This is why fulvic acid is often considered to be one of the best foliar feeds that every grower must consider using when growing cannabis plants.
You can usually buy fulvic acid in liquid form, which is easy to mix into water. Again, just follow the manufacturer’s recommendations.
Saponin, present in hundreds of plants, is an excellent foliar feed. It is antimicrobial and boosts water and nutrient uptake in cannabis plants. Saponin acts by reducing the surface tension of the solution, making the nutrient solution easier to be absorbed.
If you want to use saponin, you can either use Therm X-70 or yucca plant extracts. Therm X-70 is a natural wetting agent that is rich in saponin, and yucca plant extract contains other micronutrients like zinc, iron, copper, etc. along with saponin.
Harpin proteins work by activating a defense response in cannabis plants, which makes them more resistant to various bacterial and fungal diseases. But unlike other pesticides, it does not directly interact with fungal spores or bacteria — it boosts the plant’s systemic acquired resistance (SAR).
Boosting SAR is preferred over pesticides as it doesn't allow the bacteria or fungal spores to develop resistance over time.
Harpin proteins are safe and non-toxic, but they are relatively new, so finding them may not always be easy. One of the most popular products that contain Harpin proteins is Axiom, so look for that.
While most growers use root drench to feed cannabis plants, one must always have a foliar spray handy in their cannabis garden. It can help you help your plant overcome various problems.
Want to give your plant a nutrient boost?
Want to prevent or eliminate pests and fungi?
Want to boost your plant’s immunity?
Foliar feeding is your solution to all such problems. All you need to do is figure out what the problem is and what's causing it. With that information, find the right foliar spray, which can include a diluted version of the root drench, neem oil, aloe vera gel, or store-bought supplements.
And follow the manufacturer’s recommendations to mix them with water and use the right sprayer to mist your cannabis plants. Remember, the droplet size should be between 100 to 175 microns, and don’t forget to use a surfactant to ensure an even misting.
Foliar feeding is easy, and when done right, it can not only help your plant overcome problems but also avoid them. Use this guide as a doorway into a new form of helping your cannabis plant grow better and develop bushier buds.
