Cannabis Nutrient Deficiency Guide

Cannabis Nutrient Deficiency Guide

Nutrient deficiency is common and cannabis is a very demanding plant which requires a lot of light. When learning to grow cannabis you are likely to experience the most common nutrient deficiencies.

Nutrient deficiency is not always a major problem that can not be fixed. You must act quick to correct the deficiency as cannabis plants are fast growing. As well as, you must learn to ready the nutrient deficiency signs in its early stage.

Nutrient deficiency are be tricky to master as their are some overlapping similarities between deficiencies. To simplify the topic we will cover primarily the main deficiencies and help you eliminate other causes and effects.

Nitrogen (N):

Nitrogen deficiency can commonly found with indoor growing and is very easy to correct. Their is no major guess work when dealing with nitrogen deficiency. Typical signs begin with mild yellowing on your larger, lower, leafs (fan leaf’s). Purple lines also appear on your stems and stocks.

Nitrogen is a mobile nutrient; in which, your plant will pull energy storage from the lower leafs and provide the new growth with the nutrient requirements. Nitrogen signs also include purple markings along the stems and stocks of plants.

Cannabis nitrogen deficiency by healthy cannabis reviews
Nitrogen deficiency on fan leaf’s. Very common and easy to correct.

There are several ways to fix your nitrogen deficiency, the most common is to use non-organic fertilizers. Most cannabis growers use synthetic salts such as a hydroponic fertilizers.

Most indoor cannabis growers use synthetic fertilizers because it allows for your main macro/micro nutrients to be plant available and immediate. Your results should be apparent within one week or you may need to increase your nutrient feeding strength.

Your other feeding option is organic and will take longer to correct. Coffee grinds is the quickest fix. Adding manure or sea kelp can help correct your nutrient deficiency. Although, you best options may be to create a compost tea and water frequently. I should not have to tell you not to use human feces.

Phosphorous (P2O):

P2O, is responsible for over all cell health and DNA activity of the plant. Phosphorous is a mobile nutrient. P2O is essential to over all yield and is viewed as a macro nutrient. To make healthy clones you need good amounts of P2O available before cloning should take place.

Phosphorous deficiency signs

At first the leafs will appear darker with a unique shade of blueish tint; by which it may first appear like an abundance of N. What separates the difference between N toxicity and phosphorous is: the leafs will appear dark-dark blue with developing necrotic dead spots. The absence of purple stems may also be noted, as well as, stunted leader growth may be noticed.

Phosphorous deficiency by healthy cannabis reviews
Notice the dark green, with dead spots forming and migrating to leaf veins/stems. Soon this plant leaf will curl and drop. The leaf is approx 2 weeks of deficiency and cannot be recovered. Pluck the leaf and discard.

If your P2O deficiency continues, after several weeks the dead spots will continue to the stem; in which, the leafs will start to curl and fall off. P2O is difficult for the plant to find in nature and its best to correct with synthetic salts. If your all-organic, you can use bat guano and accept a longer response time.

P2O is absorbed best in soil-less growing at around 6.2pH level. If growing in hydroponics try to keep your pH around 5.8-6.0pH with minimal deviation. It is much easier to prevent than cure a P2O deficiency; therefor, use a well balanced soil mixture or adequate synthetic nutrients with acceptable ppm strength.

Potassium (K):

Potassium is important to the over all function of the plant. With out potassium the plant would cease all transpiration. K is mainly reasonable for keeping the plant in full operation by opening and closing the stomata. This allows the plant to breath therefor, cooling the plants internal temperature.

K is responsible for water transportation therefor, over all fitness of the plant. If your plant is moving lots of water, your plant is vigorous and in full operation. Potassium assist in the production of carbohydrates; important during flower time.

The purpose of potassium can be simplified by remembering K is important for water transportation, cooling and sugar production. In which, P2O is used more for DNA and cell operation spectrum.

Potassium deficiency signs

The nutrient deficiency(s) may look similar but separated by the causes. K deficiency results in burned leaf tips similar to salt burn. But this is because of poor cooling and the cell’s are dying. Were as, P2O deficiency effects are because of the inability to maintain cellular functions.

Potassium deficiency by healthy cannabis reviews
Notice the dying leaf tips, yellowing near the edges. This plant almost resembles nutrient burn but separated by two simple facts. Mild darkens and very small necrotic dead specs are forming. Notice the tips have a slight curl up as they are drying out.

K nutrient deficiency appears as marginal leaf tips dying. The tips will act like they are drying and may curl up therefor, inward towards the stem. You cannot fix a dead cell so it is best to prevent potassium deficiency. Furthermore, the leafs will begin to show yellowing near the tips with periodic dead spots along the blades of the leafs.

Best way to fix potassium issues is to prevent it from the start. If you have signs of K deficiency than your plant will yield less production. You should apply a higher dosage of K as a synthetic fertilizer.

If using city tap water, sometimes high sodium can react with K, making it cation bound together; therefor, not plant available. Ideally, it is always best to use rain water or RO water with synthetic nutrients to help the proccess of elimination.

Calcium (Ca)

Calcium is difficult for the plant to redistribute as it only transport calcium in one direction. This is why lower growth will show signs of deformity where as, the new growth will be slower but normal. Signs of deformity is the early sign but later stages leaf’s will also develop yellowish/brown spots.

Some similarities exists between calcium, phosphorous and potassium but make note that calcium affects lower, younger growth with deformation and than the addition of spots. In addition, the spots will start small and enlarge over time if untreated.

Calcium deficiency comparison by healthy cannabis reviews
Notice, the leaf margin death and yellow/brown spot, but wit the addition of deforming lower growth will help separate overlapping signs of deficiency.

Calcium deficiency can be corrected by several products; such as,CalMagic or CalMg+ for organic growers. These are products by General Hydroponics and can be a supplement to your current feed program. You can also increase your nutrient strength and NPK ratios to help combat deficiency.

Soil amendment is optional. Calcium can be added to the soil in the form of dolomite, hydrated lime or calcium sulfate. All thought these amendments will help resolve a calcium deficiency, this solution is more ideal towards garden beds rather than container growing.

If problem persists, investigate deeper

If calcium is a continuous problem you should monitor your growing medium EC levels and determine if your medium is to acidic. Ideally, your pH levels should be above 6.0pH but below 7.0pH. You could also check your pH run off of your medium when watering. This will help you adjust your pH levels as required when mixing nutrients.

Magnesium (Mg)

Magnesium a common nutrient deficiency. Mg is important to the plants energy transport system and works hand in hand with calcium. Typical signs are small rusty spots that can mimic specs. The important identifier is the ‘rusty’ appearance.

Signs of magnesium deficiency

Mg spots can be small and large. The spots are primarily on the supportive fan leafs. Smaller leafs may become effected during flower stage. I believe Mg is easier to identify than calcium but people often are confused with calcium deficiency.

Magnesium deficiency, rust spots by healthy cannabis review
Notice the rusty, copper looking spots? They will continue to grow and over time produce dead cell’s resulting in holes. Fixing Mg is easy but usually the issues are because of various factors such as using well water for Cal/Mag supplements.

Complications with Well Water

Well water may have high amounts of calcium and magnesium; usually these molecular bonds are to large and not plant available. I personally, specialize in water quality, water testing and chemistry. Do not let a local grower or form post fool you in believe your well water is all you need. Calcium and Magnesium must be in a plant available form.

Quick fix with Epson salts

Epson salts is a mini miracle for all growers, whether its tomato’s, basil or cannabis, Epson salts show no favoritism. Two methods will work when applying Epson salts. You can simply spray a 2% solution every 3 days or water your plants with 30ML of Epson salt per 1 gallon of water. I personally, find 20ML or 1table spoon ideal when supplementing with your nutrient feed program.

Measure nutrient temperature healthy cannabis reviews
Temperature measured with a TDS pen. The water temp is 5.8 degrees Celsius This is very cold and nutrients cannot be mixed until temperatures are above 10 degrees. One should not water your plants until temperatures are approx 15 degrees.

The major causes of deficiency is over saturated, cold soils that become acidic over time. This is why Cal/Mag deficiency usually becomes apparent in flower after your growing medium has had the chance to accumulate salts. Make sure your water is not cold when mixing frets or watering. The ideal water temperature should be 18 degrees; in which, oxygen is abundant.

Iron (Fe)

Iron deficiency can be common; Fe is immobile and relies on your feeding program. Iron deficiency is easy to fix and sometimes iron can be fixed on its own. The trick is to identify the cause.

Signs of iron deficiency

Yellow veins can be a sign of iron deficiency; but is only apparent in serious cases. Iron deficiency may look a lot like other deficiency’s; making identifying harder. Quick fixes require, increasing your nutrient ratios, nutrient strength and adjusting pH correctly typically helps. Supplementing with a Cal/Mag Plus by General Hydroponics is a common fix.

Iron deficient leaf by healthy cannabis reviews
Later signs of iron deficiency

If the nutrient deficiency does not clear up on its own or after applying synthetic feed your symptoms will become more apparent; leafs will begin to transition from yellow to whitish. After this phase, if left untreated, dead spots will develop. This should be your final clue that you have a iron deficient.

Most of the time, Fe becomes deficient because: lack of feed, pH soil issues, old nutrients, low root temperatures or coco products

You must correct all of the causes, prune the effected leafs and continue to monitor for further signs.

Best way is to use a comparison chart!

Cannabis & Opium Seeds For Sale

Chart is good for second comparison

Cannabis & Opium Poppy Seeds For Sale

Final Thought

These are the most common issues will you see within your cannabis garden. The other nutrient deficiency you may struggle with but very rarely. First eliminate these common nutrient deficiency’s than look at the other defects on the charts posted above. Feel free to place some comments or pics below or at our Facebook feed. You can post our link to other information sites if you found any info to be helpful!


Happy Growing!


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This Post Has 2 Comments

  1. Yea interesting but what nutrients strengths are you talking about, what about toxicity? U forgot to mention that.

    1. Toxicity is for another blog entry and not as common for the indoor gardener. Generally, toxicity occurs when feeding your plants when to young. This is when they become stunted; generally most growers try to use the tactic ‘less is more’ approach. I am not sure what you mean about ‘nutrient strengths’? In the mean time please review this blog entry
      If your looking for a custom feed program for clones etc you can message me or ask here.

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