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Cannabis Nutrient Guide





Cannabis Nutrient Deficiencies

One of the first things we should discuss is the difference between macroelements, microelements, and beneficial elements. Macroelements are going to be the most important nutrients to provide to your grow.  In the absence of these elements, the plant will be unable to complete its life cycle. There is no substitute for macroelements, other elements may carry out some of the same functions of macroelements or even mitigate the effects of harmful environmental factors. These elements are referred to as microelements and beneficial elements. Macroelements are Nitrogen, Phosphorus, Potassium, Sulfur, Magnesium, and Calcium. N-P-K labels pertain to Nitrogen, Phosphorus, and Potassium, also known as the Primary Macronutrients. The Secondary Macronutrients are Calcium, Magnesium, and Sulfur. Microelements are Iron, Manganese, Zinc, Copper, Boron, Molybdenum. Beneficial elements include Sodium, Silicon, Cobalt, Iodine, and Vanadium.


Correcting Nutrient Obstacles

You’ve read all about the problems one may face when giving nutrients to your plants, but how do you overcome them? The simple answer is to flush your plants. All this means is to stop giving nutrients to your plants and continue to water them normally. If your plants are showing signs of underwatering, simply water them, this will also help reduce the amount of nutrients in the soil in addition to correcting the water deficiency. It is always better to have a nutrient deficiency than excess. Deficiencies can be corrected in a short amount of time, however, removing excess nutrients from the soil will take more time and cause more damage to your plants.

Once your plants have flowered and are heading for harvest, you'll want to flush your plants regardless of any possible nutrient imbalances. To flush, simply water normally for seven to fourteen days and refrain from giving your plants any other nutrients.

What Ratio Is Optimal to Plant Growth?

This answer depends on the stage of the plant. If your plant is in the vegetative growth stage then you will want your plants to get a higher level of nitrogen, a normal dose of phosphorus, and a high level of potassium. When your plants have reached the flowering cycle, you want to aim for a lower level of nitrogen, a medium amount of phosphorus and again, a high level of potassium. This means that most growers aim for a 3:1:1 ratio, meaning three parts nitrogen, 1 part phosphorus, and 1 part potassium in the beginning phases of their plant's lifecycle. In early bloom growers typically switch to a formula with an NPK ratio of somewhere around 1:3:2, and in late bloom a ratio of 0:3:3.

The Macroelements



Most of us would assume that nitrogen is the most important nutrient for your plant’s growth cycle. You would be correct; it is the most essential nutrient of them all. It is essential to the structure of proteins within the plant. It is easy for your plant to become nitrogen deficient as most soils contain low nitrogen levels. Here are some things you’ll want to look out for in your next grow:


Nitrogen Deficiencies

The bottom leaves will start turning yellow and as time progresses more leaves will turn yellow, curl, and discolor. Your leaves are not like they used to be, they’ve begun to droop and lose their texture.  Your plants will flower prematurely and you will yield much less than the average yield of that strain.


 Nitrogen Excess

If your plants have too much nitrogen in them, your stems will grow weak, along with the foliage. This will make your plants look like they are drooping a bit and they will take a darker shade of green. The stems will weaken, which means your water transport system is also weakened, so your plant will have a harder time taking water where it needs to go. When a plant cannot distribute nutrients efficiently, you get much lower yields.



Phosphorus acts as a fuel source for the plant and is vital for the plant’s metabolism and photosynthesis. Not only that, but phosphorus essentially creates the foundation of your plant. It starts from the roots and strengthens the structure of the plant as it grows. Maintaining adequate phosphorus levels allows your plants to be able to uptake available nutrients. Without phosphorus, your plant may not gain enough strength to reach the flowering stage.


Phosphorus Deficiencies

One of the first signs of a phosphorus deficiency is that your leaves will develop a blue hue to them. Your petioles will turn purple and your plant’s growth will slow. From there it will develop copper blotches and severely affected leaves will deteriorate, wither, and drop. If you don’t adjust your plant it will become extremely weak and be much more susceptible to diseases and pests.


Phosphorus Excess

If your plant makes it to harvest with an excess amount of phosphorus, your dry buds will taste like chemicals. When your plant starts growing thin blades, droopiness, and your leaves begin to burn, you’ll know you’re giving your plant too much phosphorus. Your plants will also show signs of multiple other nutrient deficiencies.



Potassium plays a large role in osmoregulation which regulates water and salt concentrations in your plant. Potassium’s biggest role is to regulate the opening and closing of your plant's stomata, which we all know is how your plant transpires and adjusts to humidity and temperature changes.


Potassium Deficiencies

Your older leaves will turn pale, the tips of your lower leaves will look rusty and burned and the inner layers turn yellow. Flowering will diminish and your branches may become brittle.


Potassium Excess

New leaves will develop interveinal chlorosis. Spotty burns will appear on your older leaves and your roots will acidify and die back. The root tips will look burned. You’ll also notice your plant's inability to transpire correctly will sometimes make the leaves heavy if your relative humidity is on the high side.


Sulfur plays a large role in cellular respiration and protein synthesis. Sulfur helps your plants develop a tolerance to colder temperatures.


Sulfur Deficiencies

Your leaves will turn yellow from the inside out, meaning, the outer edges of the leaf will be green while the inner parts will turn yellow. If left untreated leaves can burn and stalks will begin to feel more like wood. This will lead to slow bud formation and lower yields.


Sulfur Excess

Leaf tips may burn and turn a variety of colors. Your plant will be smaller overall and yield less.


Magnesium plays a crucial role in the plant's ability to convert energy from the sunlight into nutrients that it needs. It aids in the plant's ability to generate glucose from photosynthesis and is crucial to the plant's life cycle.


Magnesium Deficiencies

This is a tough one because deficiencies can exist 4-6 weeks before symptoms arise. Internodal yellowing occurs and irregular rust spots develop on the older leaves. If left untreated your plant will look sickly in appearance when it comes time to harvest.


Magnesium Excess

Your plant will develop a dark green foliage, darker than normal. Its growth will be stunted and symptoms may point to salt toxicity.



Calcium is responsible for keeping the structure of the plant together. It helps promote healthy cell walls so the plant can develop and function as it should.


Calcium Deficiencies

Lower leaves will curl and light and dark brown spots will occur. Flower development will be slow and the harvest will be diminished if not corrected.


Calcium Excess

Uptake of some macro and microelements will be inhibited. From this, you might see some minor leaf wilt and slightly stunted growth.

The Microelements



Iron is essential for chlorophyll synthesis which ultimately aids the plant’s ability to absorb energy from light.



Manganese helps activate enzymes in the plant and helps produce chloroplasts. This may give your plant the ability to react to environmental changes in a more efficient way.



Copper aids in photosynthesis.



Boron plays an important role in cell division and amino acid production.



Molybdenum helps your plant metabolize nitrogen.


Other beneficial elements include sodium, silicon, cobalt, and iodine. These are not essential for cannabis plant growth but can provide the plant with positive attributes that are beneficial come harvest time.

Grow Your Own Medical Marijuana in Missouri

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