Bat Guano for Cannabis: What It Is and How to Use It

What is bat guano?

Bat guano is bat poop, and it's one of the oldest organic fertilizers around. Guano is the droppings of bats, seabirds and other colony-dwelling animals, and it's prized by growers because it's packed with the nutrients plants need to grow and flower. For cannabis, bat guano is mostly used as an organic boost during bloom.

Bat guano in particular is widely used in farming and gardening as an organic fertilizer. It brings a rich mix of nitrogen, phosphorus and potassium, plus other minerals and trace elements that plants love. Thanks to that makeup, it's especially popular during the flowering stage, since it helps plants put out more flowers and fruit.

You can find bat guano as a powder or in pellets, and you can apply it straight to the growing medium or mix it in. Follow the manufacturer's directions or recommended rates, because too much guano can hurt your plants.

One important thing to keep in mind: as effective as guano is, it should be harvested and sold in a sustainable, eco-friendly way that protects the bat colonies and other animals that produce it.

What is bat guano good for in a cannabis grow?

Bat guano is a natural fertilizer that's widely used in cannabis growing because of what it does for the plants. Growers value it most for its high content of the essential nutrients cannabis needs to grow and develop.

These are some of the main perks of using bat guano on cannabis:

1. Nutrient-rich feeding: Bat guano contains a mix of nitrogen, phosphorus and potassium, plus other essentials like calcium, magnesium and zinc. These nutrients are key for vigorous growth and for building flowers and fruit.
2. Boosts flowering: Bat guano is especially recommended during the flowering stage. Its high phosphorus content helps develop bigger, denser, more resinous flowers, which means more buds at harvest.
3. Improves soil quality: As an organic fertilizer, bat guano also helps improve soil structure and health. It adds organic matter that feeds microbial life and helps the soil hold on to nutrients, creating a better environment for your plants.
4. Safe, sustainable nutrition: Bat guano is a natural fertilizer that's easy on the environment. Since it comes from bat droppings, it can be collected sustainably without any synthetic chemicals involved.

What nutrients does a cannabis plant need?

A cannabis grow needs a combination of essential macronutrients and micronutrients.

The big three nutrients cannabis needs to grow are NPK, short for nitrogen, phosphorus and potassium. NPK is the foundation of every cannabis fertilizer and of every thriving weed plant. Cannabis also needs carbon dioxide and oxygen, which it gets from airflow, and hydrogen, which comes from water.

Cannabis plants also need secondary nutrients, including sulfur, calcium and magnesium.

Finally, there's a wider group of micronutrients that keep growth going. These essential micronutrients include zinc, manganese, iron, boron, chloride, cobalt, molybdenum and silicon, among others.

How and when should you fertilize cannabis plants?

Cannabis plants need different nutrient levels depending on their growth stage. In general, cannabis fertilizer is applied at least once a week, along with plenty of pH-balanced water.

As a rule of thumb, the ideal pH for cannabis grown in soil is between 6.0 and 6.8. Hydro growers need to keep their water pH between 5.5 and 6.5.

How to feed cannabis at each growth stage

Seedling: little to no fertilizer. It's best to wait until a few sets of leaves have come in before giving the first dose of NPK fertilizer.

Vegetative: in week 1, use an NPK ratio of 2:1:2, meaning two parts nitrogen to one part phosphorus and two parts potassium. By week 7 you can bump the ratio up to 10:5:7, followed by 1:1:1 in late veg.

Flowering: at this stage, focus on raising phosphorus and potassium. Feeding helps most in early flower, and it's much less effective in the final weeks once the real buds have formed.

Pro tip: not all feeding charts are created equal. Start with less than the recommended dose and work your way up to avoid overfeeding or nutrient burn.

What is fertilizer, exactly?

Put simply, fertilizer is plant food made from natural or industrially produced substances that growers apply to soil and plants to get the best growth. The nutrients in fertilizer can benefit all kinds of plants, including houseplants in containers.

Why does fertilizer matter for cannabis plants?

The nutrients in fertilizer help growers pull off a healthier harvest, with more leafy growth and, eventually, more flowers. If you're after big buds, the right fertilizer can help you get there. Without good nutrition, your cannabis buds may never reach their full potential.

What's the best type of fertilizer for organic growers?

If you want to grow organically, you can use a natural cannabis fertilizer made with the following:

• Beneficial bacteria and fungi
• Humus
• Fish meal
• Blood meal
• Bat guano