The Cannabis Nutrients Required to Fuel Significant Growth

Success in cannabis cultivation hinges on recognizing and providing each cultivar with the appropriate mix of nutrients to support development from germination through flowering. Too often, nutrients are approached like steroids for plant growth instead of the nutritious mixture of food they need to mature and thrive.

When growers overdo it with essential nutrients like nitrogen, a building block for amino acids and chlorophyll to provide plant structure and capture sunlight, they end up with impressive shiny green leaves and small buds. According to a controlled study published in the National Library of Medicine, being overly cautious with magnesium (Mg) in the vegetative growth phase results in low morpho-physiological function and reduced biomass. 

Without the right food at each stage of growth, cannabis gardens will fail to reach their full potential. Cannabis nutrients typically fall into four categories: micro or macronutrients, and mobile or immobile nutrients.

1. Macronutrients are essential building blocks for plants consumed in large quantities.
2. Micronutrients are critical for a plant’s biological functions. They’re required in lower concentrations. 
3. Mobile nutrients are able to move through plants. Mobile nutrient deficiency and toxicity often show on older leaves.
4. Immobile nutrients are not able to move throughout the plant. Immobile nutrient deficiency and toxicity often show on young leaves.

Anytime a growing medium slips out of the optimal pH range, nutrient lockout can occur as plants struggle and eventually fail to absorb nutrients. In most growing mediums, cannabis grows happily with a pH range of 5.8-6.3. However, this range is subject to change based on the feeding schedule and growing medium.

Other than light, water, and carbon dioxide, all plants require a similar mix of nitrogen (N), phosphorus (P), and potassium (K). For convenience, these three nutrients are referred to as NPK. In cannabis cultivation, mastering the elemental trio leads to large buds with a deliciously smooth smoke. Without the right mix of NPK throughout the growth cycle, cannabis plants struggle with essential functions including photosynthesis and cell development, leading to a multitude of undesirable outcomes.

N-P-K

NPK ratios vary depending on the growth stage. During vegetative growth, nitrogen is emphasized with an NPK ratio of three-one-two, meaning three parts nitrogen, one part phosphorus, and two parts potassium. Once buds start to form, the ideal ratio shifts to emphasize phosphorus with one-three-two. In the final weeks of the vegetative stage (also known as ripening), many growers opt for a zero-three-three ratio.

A nutrient deficiency during the vegetative stage can be relatively easy to spot. One telltale sign is yellowing leaves. If you see this, make sure to test the pH of your water immediately and adjust accordingly so your plant can absorb nutrients appropriately.

When it comes to nutrients, the growing medium will play a big role in how you feed the plants. When using soil, the plants will absorb essential nutrients from the ground automatically. Instead of applying nutrients, some growers add things like bat guano to the soil, which will adjust the microbiome naturally. The plant’s root system will be able to uptake whatever it needs, making precision dosing less critical when delivering nutrients in the soil.

In hydroponic cultivation, such as with coco coir or rockwool, nutrients are delivered directly to the plants via water. It is essential to maintain precision and equilibrium in the feeding regimen.

Organic vs. synthetic nutrients

In organic farming, nutrients are applied directly to the soil, where microbes, amino acids, and fungi convert these materials into forms that plants can absorb. Conversely, synthetic nutrients are formulated to be immediately accessible for plant uptake.

When using synthetic nutrients for cannabis, opting for smaller pots and increasing watering frequency can help optimize the drying process for more effective crop management. Organic cannabis nutrients like Advanced Nutrients Big Bud Organic tend to require a much larger pot size and prefer constant moisture with very little dry back.

Macronutrients

Macronutrients are the nutrients the plant will use in the most abundance during its life cycle. These nutrients are oxygen, hydrogen, carbon, nitrogen, phosphorus, and potassium. All of these nutrients are required throughout the life cycle, but the plant will use more nitrogen during the vegetative stage of growth.

“Nutrient requirements vary throughout the cannabis life cycle,” said Wisconsin-based commercial cultivator, Kurt Kinneman. “As the plants begin to flower and finish, the nitrogen use will decrease, and the phosphorus and potassium use will go up as plants begin to focus on flower and production instead of leaf and stem production.”

N, P, and K are all mobile nutrients. This means deficiencies first will appear in older leaves and stems as the plants use those nutrients to keep pushing new growth. If the deficiency is not corrected, new growth will start showing signs of a deficiency.

In addition to the main macronutrients, plants also require three secondary macronutrients: calcium, magnesium, and sulfur. Calcium improves the absorption of other nutrients by the roots and helps move them throughout the plant. It’s also an essential building block for enzyme functions.

Calcium also helps soil-dwelling organisms break down organic matter into usable nutrients for plants and helps nitrogen-fixing bacteria grow nodules on plant roots to fix atmospheric nitrogen in the soil.

Micronutrients

Micronutrients may only appear in trace amounts in plant matter, but they play a big role in overall function. When any micronutrients are lacking, overall plant health and yield can suffer. However, it’s similarly important to avoid an overabundance of micronutrients, which can cause toxicity that also can be detrimental to overall crop yields.

Boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), and chlorine (Cl) are some of the most abundant micronutrients. They are all crucial to crops but may only be present in small amounts.

When trying to dial in the right mix for a new cultivar, it’s important to keep variables to a minimum for accurate results.

“Go slowly and adjust as little as possible to limit the number of variables you’re dealing with,” said Ben Lind, chief science officer at Humboldt Seed Company. “A really great tool is plant sap analysis, you can get a report back within a week that shows you different ratios of macronutrients and micronutrients with a roadmap for maximizing your ability to crop steer.”

Best nutrients for veg stage

During the vegetative growing cycle, it is important to look for a weed nutrient solution blend that has a high nitrogen concentration. When growing with synthetic nutrients, there typically will be a special vegetative blend.

“Heavy 16 is a cannabis nutrient brand that has a special feeding chart they provide with their five-part nutrient line,” Kinneman added.

When growing organically, you want to use inputs like feather meal that have a high nitrogen content. You also will want to use fermented plant extracts made from vegetative growth. Kinneman suggests hemp, comfrey, and nettle alongside the best cannabis nutrients.

Many organic growers use compost tea to help promote a healthy microbiome. When brewing compost teas during vegetative growth, it’s important to create a tea with high microbial content instead of high fungal content. It’s the opposite for the flowering stage of cannabis cultivation.

Best nutrients for flowering cannabis

The macronutrients phosphorus and potassium are essential to promote flower growth and bud production. In addition to helping grow large flowers, these macronutrients are required for root growth and promoting overall nutrient uptake.

Calcium and silica help build and strengthen cell walls to support big flowers and protect against infection and disease. These critical micronutrients also enable other nutrients to be absorbed more readily.

“While I am a firm believer in a holistic approach to gardening, if I had to choose a single nutrient most associated with maximizing yield, it would be phosphorus,” said Alexandria Irons, cannabis educator and owner at Queen of The Sungrown. “During the flowering phase, plants use an extraordinary amount of ATP (adenosine triphosphate), often referred to as the energy currency of the plant. This molecule consists of three phosphate groups, and the increased phosphorus demands during flowering are essential to support the metabolic changes driving bud development. Although more phosphorus is needed to ensure dense buds, it’s important to remember that nutrients interact synergistically or antagonistically with each other, so maintaining a proper balance is key.”

Good bud building blocks

1. Cannabis can grow wild like a roadside weed, but feeding plants the proper inputs can change weed into top-shelf flower.
2. Nutrients are critical in promoting healthy growth that leads to resinous nugs, but they’re not the only part of the equation.  
3. Mastering the art of balance is critical when applying these elements. There’s an art and science to proper feeding for each cultivar, stage of life, and growing medium. 
4. Make time to visually inspect plants daily for signs of trouble. That includes testing and adjusting the pH level to ensure optimal nutrient levels and perfect harvests.