Foliar Feeding Cannabis: How and When to Spray Your Plants

Foliar feeding means spraying a diluted nutrient solution directly onto cannabis leaves, which absorb it through their pores (stomata). Roots in the soil or another growing medium are still the plant's main way of eating, but a foliar spray is a fast, effective short-term boost, especially for secondary nutrients like magnesium and calcium. It's also a great way to deliver zinc, iron, manganese and other micronutrients.

What Is Foliar Feeding?

What makes foliar feeding so useful, and such a good fix for nutrient deficiencies in cannabis, is speed: a spray gets nutrients into the plant much faster than feeding the soil through your watering.

Most nutrients sprayed directly on cannabis leaves are absorbed in a very short time, and the plant takes up a much larger share of them this way. Some growers cite figures of up to 95% uptake for foliar feeding. In other words, the plant absorbs nearly everything you spray on, while it takes up a smaller share when fed through the soil.

Benefits of Foliar Feeding Cannabis

• When a cannabis plant takes in nutrients through its leaves, it releases more carbohydrates into the root zone. That feeds the microorganisms in the growing medium that help the plant absorb nutrients.

• Another perk of foliar feeding is that it sidesteps nutrient buildup in the soil. When salts build up, soil pH drops and your plant can end up with nutrient lockout. Spray the whole plant, especially the undersides of the leaves. That's also where a lot of pests, like mites and spider mites, like to hide.

Caring for Your Cannabis Plant: Get the Nutrient Strength Right

Always check the recommended foliar concentration on each product before you spray your cannabis plants. Most of the time, foliar feeding calls for a much weaker solution than feeding through the soil. If the label doesn't give a foliar rate, start at half strength. To avoid risking the whole grow, test-spray a single leaf first, then wait a day to see whether it caused any damage before treating the whole plant.

During flowering, it's best to skip foliar sprays, since buds can pick up nasty flavors and the extra moisture raises the odds of mold.

How Does Foliar Feeding Work?

Foliar feeding is a technique where you apply a nutrient solution directly onto the leaves of the cannabis plant. You'll also hear it called foliar spraying or foliar application. Delivering nutrients this way can be very effective and is a great way to tackle almost any kind of nutrient deficiency.

Most nutrients sprayed directly on the leaves are absorbed very quickly, and plants take up a much larger share of them this way. On top of that, when a plant feeds through its foliage, it releases more carbohydrates into the root zone, which benefits the microorganisms in the growing medium that help with nutrient uptake.

What's the right foliar feeding dose?

Foliar feeding has to be done right and at the correct dose, or you can damage the leaves. So read the product instructions carefully and follow the recommended rates. It's also important to spray every part of the plant, especially the undersides of the leaves, where most of the stomata are.

What Happens if It Rains After You Foliar Spray?

If you foliar feed during flowering and it rains afterward, the rain can wash off the nutrient solution you just sprayed. The extra moisture also raises the risk of mold on your plants. So be careful about spraying before rain: if rain is in the forecast, skip the foliar application to avoid wasting nutrients and inviting mold.

Keep in mind, too, that cannabis plants shouldn't be left out in the rain during flowering, since it can hurt bud size and quality. In general, pay close attention to how you care for your plant, including foliar feeding during flowering, so it grows healthy and produces quality buds.

When Should You Foliar Feed Cannabis?

You can foliar feed at different stages of the grow, depending on what you're trying to achieve. During veg, for example, it can help build strong foliage, and some growers use it in flowering to boost flower production and quality. Either way, spray when light is low, ideally at the end of the day, so intense sun doesn't burn the wet leaves. Use lukewarm water and spray the undersides of the leaves for better nutrient absorption.

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