What Does Fertilizer Do for Cannabis? Nutrients, PPM and How to Mix a Feed

Fertilizer gives cannabis plants the nutrients their growing medium can't supply on its own, mainly nitrogen, phosphorus and potassium plus secondary nutrients and micronutrients, so they can grow healthy and pack on quality buds. It plays a crucial role in any cannabis grow, and with the right use of fertilizers, organic ones included, growers can seriously boost their plants' development, yield and quality.

But what exactly do fertilizers do, homemade or store-bought, and how do they help cannabis plants? Let's dig into why fertilizer matters in a cannabis grow, how it feeds growth and development, and the different nutrients it delivers for a successful harvest.

Types of nutrients cannabis plants need

Growing cannabis takes close attention to nutrients to keep plants developing well through every stage of growth. These nutrients fall into two groups, macronutrients and micronutrients, and each plays a key role in plant growth and health.

Plants need macronutrients in larger amounts, while micronutrients, though needed in smaller doses, are just as important for metabolic functions like making enzymes and vitamins.

Primary and secondary macronutrients for your cannabis grow

Macronutrients are split into primary and secondary. The primary macronutrients include:

• Carbon (C), Oxygen (O), Hydrogen (H): The building blocks of photosynthesis and cell structures.
• Nitrogen (N): Crucial for vegetative growth; it drives the development of green leaves and stems.
• Phosphorus (P): Essential for root development, flowering and seed formation.
• Potassium (K): Important for protein synthesis, water regulation and overall plant strength.

The secondary macronutrients, just as important, are:

• Calcium (Ca): Helps build cell walls and gives the plant structural stability.
• Magnesium (Mg): The central component of the chlorophyll molecule, vital for photosynthesis.
• Sulfur (S): Important for building amino acids and proteins.

Micronutrients

Micronutrients, needed in smaller amounts, are crucial for keeping cannabis plants running smoothly. They include:

• Iron (Fe): Essential for chlorophyll production and photosynthesis.
• Copper (Cu): Involved in lignin production and disease protection.
• Manganese (Mn): Important for photosynthesis and fatty acid synthesis.
• Zinc (Zn): Helps with protein synthesis and plant growth.
• Molybdenum (Mo): Needed to convert nitrates into ammonia.
• Boron (B): Involved in building cell walls and in pollen germination.
• Chlorine (Cl): Essential for ion balance and osmoregulation.
• Silicon (Si) and Sodium (Na): Less critical, but they can improve disease resistance and nutrient uptake.

How to feed cannabis at each growth stage

The ratio and type of nutrients cannabis plants need change with each growth stage: rooting, vegetative growth or flowering. It's crucial to adjust the nitrogen-phosphorus-potassium (N-P-K) ratio to keep up with the plants' shifting demands.

On top of that, things like the condition of your growing medium, the size of your container, the health of the root system and the environment all affect how much and what kind of fertilizer you need for healthy growth and a big harvest.

How to mix fertilizer for your cannabis plants

Feeding your weed plants is an essential part of a successful harvest. But one feeding mistake can hurt both the quality and the quantity of your yield. The good news: mixing fertilizer for cannabis is simple if you follow the right steps:

Prepping the water and mixing nutrients for container plants

1. Prep the water:
   • Bring the water to about 19–21 °C (66–70 °F). That temperature range is ideal for nutrient uptake by the roots.
2. Add the nutrients:
   • Follow the product label to add the right amount of fertilizer to the water. Mix the solution well so the nutrients are evenly distributed.
3. Measure PPM and EC:
   • Use a PPM (parts per million) or EC (electrical conductivity) meter to get an accurate reading of the nutrient concentration in your solution. That'll help you fine-tune feeding to what your plants need.
4. Adjust the pH:
   • Adjust the pH of your nutrient mix if needed. You can use pH-down products, like nitric or phosphoric acid, until you hit the level recommended by the fertilizer manufacturer.
5. Feed your plants:
   • Once your PPM, pH and water temperature are where they should be, apply the nutrient solution to your plants. Be sure to measure the PPM or EC of the runoff to check that your plants are actually taking up the nutrients.

Why PPM, pH and water temperature matter

PPM and EC are the key measurements for figuring out how many nutrients are in your water or growing medium. Keeping them in the optimal range is crucial to avoid both overfeeding and nutrient deficiencies. pH and water temperature also play a huge role in how well your plants can absorb nutrients. Always adjust your nutrient solution to the pH the manufacturer suggests, and keep the water between 19 and 21 °C (66–70 °F).

Pro tips for better feeding

Use chelates:

• Chelates are compounds that make it easier for plants to absorb mineral nutrients like iron and zinc. You can use synthetic chelates found in high-quality fertilizers, or natural chelates like humic and fulvic acid if you prefer an organic grow.

Try foliar feeding:

• Foliar feeding, spraying a nutrient solution directly onto the leaves, works well for fixing nutrient deficiencies in the short term, especially for secondary nutrients and micronutrients.

Always flush before harvest:

• It's crucial to flush the roots with pH-neutral water at least a week before harvest. This helps clear out any built-up fertilizer residue, giving you buds with a cleaner taste and smoother smoke.

These steps and tips will help you mix and apply fertilizers the right way, making sure your cannabis plants get every nutrient they need for healthy growth and a heavy harvest.