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What are Cannabis Nutrient Deficiencies?

Simply put, nutrient deficiencies are when your cannabis plant doesn’t have access to essential nutrients and minerals required for healthy growth. Since cannabis plants are vulnerable to their nutrients, you’ll find that missing even a single nutrient can have profound effects on your plant’s appearance.

In turn, your plant may not yield as much cannabis. Not to mention, the quality can be greatly diminished. In worst cases, your plant won’t survive.

Luckily, cannabis plants are able to communicate with us when they’re lacking in deficiencies through their appearance. The purpose of this guide is to give you the knowledge required to identify when plants are deficient and how to resolve these issues.

The Basics of Cannabis Deficiencies

Before diving into specific nutrients your cannabis plant requires, it’s important to ensure all other aspects of their environment are taken care of. This includes:

pH Levels

It’s essential your plants are set in the perfect pH range. Even if you’re providing all the nutrients they need, a pH range that’s too acidic or too alkaline will prevent nutrients from absorbing at a root level.

If you’re growing your marijuana in soil, your pH range should be between 5.8 to 6.8. With 6.3 being the perfect range for cannabis plants.

Usually, pH ranges aren’t a top concern for growers as the soil tends to buffer itself to the proper ranges. Still, it’s always worth checking your pH range regularly.

Water Supply

If you’re watering plants through your local water supply, it’s essential to know the natural pH ranges of that water. These will vary depending on a number of factors, from the time of year to the weather (i.e. rainfall). While changes tend to be slight, it’ll make your life easier if you understand the pH levels of your local water and how they alter regularly.

From there, it’s important to understand what minerals are in your water. Typically, water is high in certain minerals and low in others – however, the exact minerals one water supply is high in will vary from another.

Naturally, you’ll want to supplement your cannabis plant with whichever minerals your water supply is lacking.

Still, most growers prefer using fully deionised water. This is a special type of water that’s been filtered specifically to ensure that all mineral ions are removed. This is a preferred starting point for most growers as it allows you to determine the exact mineral amounts your plants are receiving.

However, fully deionised water is typically only used among professional growers looking to have full control of their cultivation. If you’re growing marijuana at home, tap water is more than suitable. It’s simply worth noting that it may be causing some of the cannabis nutrient deficiencies you’re noticing.

Macronutrients and Micronutrients

When it comes to nutrients themselves, the cannabis plant requires specific kinds of nutrients and varying levels of each. In order to properly identify these, we refer to terms such as macronutrients and micronutrients.

Macronutrients are the type of nutrients your cannabis plant requires high amounts of. The most notable are Nitrogen, Potassium, and Phosphorus.

Your plants will also need micronutrients but in smaller quantities. The most notable include Copper, Silicon, Zinc, and Sulphur.

Mobile Nutrients and Immobile Nutrients

The difference between mobile and immobile nutrients is subtle but essential to ensuring the health of your plants. Simply put, mobile nutrients (such as Nitrogen) will transfer from one part of the plant to another. Immobile nutrients (such as Zinc) typically don’t transfer around and will remain in one area of the plant.

If you believe your plant is lacking in nutrients, it can help to identify whether that nutrient is mobile or immobile. An easy means to this is looking at the leaves. Mobile nutrient deficiency will typically effect older leaves whereas immobile nutrient deficiency will effect newer ones.

How to Identify Nutrient Deficiency

Identifying cannabis nutrient deficiencies is essential to your plant’s health. When a plant becomes sick, it will reveal this to you through its appearance. And by taking a close look at this altered impression, you can identify which nutrient your cannabis plant is deficient in.

Nitrogen Deficiency

As a mobile macronutrient, Nitrogen provides your plants with protein while also aiding in the process of photosynthesis.

When a cannabis plant is Nitrogen deficient, it will react in the following manners:

  • Shorter and smaller leaves
  • Lower leaves turn yellow and begin to fall off
  • Yellowing slowly progresses to upper leaves
  • Smaller yields and premature flowering

When a cannabis plant has excess Nitrogen, it will react in the following manners:

  • Stems and foliage become weak
  • Plants have more difficulty transferring water
  • Lower leaves coloring will turn into a deeper/darker green
  • Harvest will have a “green” taste

In order to treat Nitrogen deficiency, you can use a standard nutrient (which tends to be high in Nitrogen). This is especially true for fish-based nutrients.

It may also be worth switching to a Nitrogen-rich foliar feed spray as cannabis leaves will absorb small amounts of the nutrient.

Nitrogen Cannabis Nutrient Deficiencies

Potassium Deficiency

As the main mobile macronutrient used by the cannabis plant, Potassium is essential in transporting sugars and simple carbohydrates throughout the plant. It also helps with cell division and root growth.

When a cannabis plant is Potassium deficient, it will react in the following manners:

  • Older leaves suffer chlorosis and turn pale
  • Tip of leaves turn a rusty color
  • Increase in branching stems
  • Stems become weak, sometimes brittle
  • The number of cannabis buds diminishes

When a cannabis plant has excess Potassium, it will react in the following manners:

  • Blades on new leaves become thinner
  • Leaves start to tip and develop marginsburns
  • Lower leaves curl and develop spots
  • pH drops in root zone, causing root tips to die black
  • Causes other nutrient deficiencies (such as Zinc and Iron)

When a grower believes their cannabis is lacking in Potassium, they tend to flush their grow medium. This also ensures there are no other problems with the plant.

A great way to do this is by using chicken manure as a top dressing. If your plant is deficient in both Nitrogen and Potassium, organic seaweed can be a beneficial foliar feed.

Potassium Cannabis Nutrient Deficiency

Calcium Deficiency

As an immobile micronutrient, Calcium helps to fortify cell walls which properly develop the entire plant structure. It also helps with the transfer of Nitrogen and sugars.

When a cannabis plant is Calcium deficient, it will react in the following manners:

  • Flowers develop at a slower rate
  • Leaves and margins develop a yellowish-brown color with spots
  • Overall harvest is reduced
  • Lower leaves will curl and contort
  • Root tips might die black

When a cannabis plant has excess Calcium, it will react in the following manners:

  • Overall growth may be stunted
  • Some leaves may wilt
  • Other nutrients (such as Potassium and Iron) will be blocked

In order to treat Calcium deficiency quickly, most growers use a Calcium/Magnesium nutrient supplement. Furthermore, some also add a hydrated line to about 4 liters of water for feeding.

However, if you haven’t experienced Calcium deficiency, it’s best to take preventative measures as a safety precaution. In order to do so, simply add powdered dolomite lime to your grow medium.

Calcium Cannabis Nutrient Deficiency

Phosphorous Deficiency

As a mobile macronutrient, Phosphorous helps in the formation of plant proteins and plant DNA. Furthermore, it’s required in order for proper photosynthesis to occur.

When a cannabis plant is Phosphorous deficient, it will react in the following manners:

  • Leaves turn bluish-green and petioles turn purplish
  • Lower leaves become a dark copper color
  • If severely affected, lower leaves will develop a metallic purple color
  • Slower overall vertical and lateral growth
  • The plant becomes more susceptible to disease and pests

When a cannabis plant has excess Phosphorous, it will react in the following manners:

  • New leaves will grow thinner blades
  • Older leaf tips and margins may burn
  • Lower leaves curl and produce spots
  • Dry bud may have a “chemical” taste
  • Other nutrients (such as Calcium and Zinc) will also become deficient

In order to treat Phosphorous deficiency, you can always add a Phosphorus-rich feed/fertilizer (with fish meal or worm castings as an organic alternative).

Phosphorous Cannabis Nutrient Deficiency

Boron Deficiency

As an immobile macronutrient, Boron works directly with Calcium to create healthy cell walls and sustainable cell division. Since the cannabis plant only requires a small amount of Boron, deficiencies of this nutrient are rare.

Still, when a cannabis plant is Boron deficient, it will react in the following manners:

  • Abnormal growth in the stems, tips, and roots
  • Growth shoots may contort or appear burned
  • Spots appear between leaf veins
  • Leaves become thick and brittle
  • Stems develop a rust color
  • Roots swell and become discolored

When a cannabis plant has excess Boron, it will react in the following manners:

  • Leaf tips will first yellow, then appear burned
  • Yellow leaves will fall from the plant

If your plants are Boron deficient, you’ll need to flush your growth medium and then add extra Boron to the new solution. This is preferably done with a teaspoon of Boric acid in 3 to 4 liters of water.

Boron Cannabis Nutrient Deficiency

Magnesium Deficiency

As an immobile micronutrient, Magnesium creates the significant chlorophyll pigment, an essential component of photosynthesis. In fact, without Magnesium, photosynthesis cannot happen.

When a cannabis plant is Magnesium deficient, it will react in the following manners:

  • Middle-aged leaves will yellow and develop rust-brown spots
  • Older leaves will dry out, curl up, and fall
  • Overall, the plant will develop a sickly appearance

It’s important to note that when a plant becomes Magnesium deficient, it will appear normal for about 4 to 6 weeks. From there, the above-mentioned characteristics will begin to appear.

When a cannabis plant has excess Magnesium, it will react in the following manners:

  • The overall growth of the plant will be stunted
  • Foilage will become dark green

When it comes to Magnesium deficiency, the most common solution is epsom salt. By adding a teaspoon to a liter of water, your plants will be given an extra boost of Magnesium.

Still, you should double-check a water analysis of your supply. In many places, the water supply already provides plants with the efficient amount of Magnesium.

Magnesium Cannabis Nutrient Deficiency

Copper Deficiency

As a semi-mobile (holds characteristics of mobile and immobile nutrients) macronutrient, Copper allows the plant to employ Nitrogen. It also helps in the metabolism of carbohydrates.

Similar to Boron, Copper deficiencies are rare. This is due to the fact that grow mediums and feeds tend to have enough Copper to meet your plant’s necessities.

Still, when a cannabis plant is Copper deficient, it will react in the following manners:

  • Young leave shoots will contort and sometimes die with black coloring
  • Leaf tips and margins will develop a dark green and copper grey color
  • Furthermore, leaf tips and margins may die black
  • Overall growth slows down, reducing yield size

When a cannabis plant has excess Copper, it will react in the following manners:

  • Overall growth slows down
  • Reduction in the number of branches
  • Root growth slows, with existing roots becoming thicker and decaying

In order to treat Copper deficiency, you’ll need a feed that contains sufficient levels of Copper. However, it’s much easier to ensure prevention measures (by formulating the perfect environment for your cannabis plant) than fixing a Copper deficiency issue.

Copper Cannabis Nutrient Deficiency

Iron Deficiency

As a semi-mobile macronutrient, Iron helps with the production of chlorophyll while also assisting in nitrates and sulfates. Typically, Iron deficiencies only occur when pH levels are out of range, or when there’s excess Zinc, Manganese, or Copper.

When a cannabis plant is Iron deficient, it will react in the following manners:

  • Overall growth is slowed with a reduced harvest
  • Starting at the opposite end of the leaf tip, young leaves will develop interveinal chlorosis
  • If Iron deficiency progresses, larger leaves will also become interveinal chlorosis
  • Leaves may drop

When a cannabis plant has excess Iron, it will react in the following manners:

  • Leaves become a bronze color with dark brown spots
  • Signs of Phosphorous inhibition appear in lower leaves

The best way to prevent Iron deficiency in cannabis plants is to ensure pH levels always remain within the acceptable range.

Iron Cannabis Nutrient Deficiency

Manganese Deficiency

As an immobile micronutrient, Manganese plays an essential role in cell function. More specifically, it aids in nitrogen use, respiration, and photosynthesis.

When a cannabis plant is Maganese deficient, it will react in the following manners:

  • Leaves will initially show signs of interveinal chlorosis
  • Dead spots will appear on affected leaves, causing them to eventually fall off
  • Leaf margins will become dark green

It’s worth noting that Maganese deficiencies begin in younger leaves, eventually spreading to older ones.

When a cannabis plant has excess Maganese, it will react in the following manners:

  • Younger (and newer) leaves will develop dark orange to rustic brown coloring
  • Younger leaves will develop tissue damage, eventually spreading to older leaves

Since Maganese deficiencies are rare, there’s no real solution to an already existing problem. However, in order to prevent such deficiencies, it’s essential to ensure pH levels are adequate and there’s not an excess of Iron.

Manganese Nutrient Decifiency

Molybdenum Deficiency

As a mobile micronutrient, Molybdenum helps in the functioning of enzyme symptoms and in the conversion of nitrates to ammonium compounds. Similar to the above-mentioned nutrients, Molybdenum deficiencies are rare.

When a cannabis plant is Molybdenum deficient, it will react in the following manners:

  • Leaves become distorted and eventually drop
  • Older and middle-aged leaves may become yellow, a potential sign of interveinal chlorosis

When a cannabis plant has excess Molybdenum, it will react in the following manners:

  • Leaves become discolored
  • Iron deficiencies

There are no sufficient treatments for Molybdenum deficiencies. Instead, prevention is the best measure.

Molybdenum Cannabis Deficiency

Silicon Deficiencies

As an immobile micronutrient, Silicon is a mineral that aids in strengthening cell walls. This allows for sturdier growth and an overall stronger plant.

Cases of Silicon deficiencies are extremely rare. This is due to the fact that most feeders have sufficient levels of Silicon.

Still, if you believe your plant is lacking in Silicon, specialist liquid Silicon feeds are available. However, most growers use this in order to develop stronger plants.

Sulfur Deficiency

As an immobile micronutrient, Sulfur is critical for important enzymes and proteins. In fact, your cannabis plant needs Sulpher for the sake of respiration, photosynthesis, and fatty acid breakdown. Not to mention, it plays an essential role in the development of terpenes.

When a cannabis plant is Sulfur deficient, it will react in the following manners:

  • Flowers become weak and take longer to develop
  • Young leaves will have stunted growth, with a lime-green to yellow color
  • If Sulfur deficiency progresses, leaf veins will yellow too
  • Along the stem, purple streaks may appear and develop a woody appearance
  • Leaf tips may burn, darken, or slope

When a cannabis plant has excess Sulfur, it will react in the following manners:

  • Overall, plants will develop at a slower rate
  • Leaf tips and margins may discolor (in severe cases, they may burn)

Sulfur deficiency is often caused by low levels of Phosphorous and therefore, requires a Phosphorus-rich feed/fertilizer. However, it can also be caused by high pH levels around the roots of the plant.

Sulfur Cannabis Nutrient Deficiencies

Zinc Deficiency

As a metallic immobile micronutrient, Zinc is essential in a cannabis plant’s production of sugar and protein. Zinc also aids in the production of chlorophyll which creates healthier stem growth.

When a cannabis plant is Zinc deficient, it will react in the following manners:

  • Young (and new) leaves will develop interveinal chlorosis, causing contorted thin blades
  • Stem tips will stop developing, causing them to “bunch up”
  • Leaf tips discolor and burn, which may happen to margins if deficiency progresses
  • Stunts overall growth and produces fewer buds

When a cannabis plant has excess Zinc, it will react in the following manners:

  • Will cause the plant to die quickly
  • Inhibits Iron’s ability to function

Zinc deficiencies are most common in dry climates, especially where there are high amounts of alkaline in the soil. Since it’s only required in small quantities, the best treatment is replacing your growth medium.

Zinc Cannabis Nutrient Deficiency

Frequently Asked Questions