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Nutrients & Deficiencies

In a previous blog post I wrote about feeding Cannabis, sometimes even when you follow directions problems may arise with yours plants. This allows you to spot the issue and fix it.

A usual issue is yellowing of the leaves occurs in lower leaves this is a Nitrogen deficiency. They will turn soft, curl in or crinkle and eventually turn brown. When the plant doesn’t get enough nitrogen it will pull it from the lower leaves, causing them to yellow and die. It should only be the lower leaves if its the upper new growth that’s normal.

Nitrogen moves through out the plant as needed, when it is low leaves use it up in other parts of the plant that require it the most like new growth. The plant will push the nitrogen to these parts to help them with photosynthesis and keeping it green. It is normal for the plant to start yellowing in late flowering cycle. If it yellows in vegetative then you have a issue.

Solution: Feed the plant with a good nitrogen nutrient and adjust pH.  I recommend any complete nutrient should help. I use General Organics or Bat Guano for soil and for hydroponic I use General Hydroponics FloraGro or Advanced Nutrients pH Perfect. Also be sure to not over feed with Nitrogen because you will get toxicity and that shows when the leaves are very dark.

Issue: Edges appear brown or burnt, Pale, Brown spots, yellow spots, Dark or purple leaves, slow growth.


This is a Boron deficiency usually occurs in a dry environment or under watered. First sign will be thick grow tip or growth twisting or abnormal. yellow or brown spots will show and root growth will be slow.

Solution: Use a balanced nutrient and make sure your feeding regularly and that its not too dry in the growing room. Make sure your pH is adjusted correctly since Boron is used by the plant at a lower pH so when it rises the Boron isn’t available to the plant. Use a Hygrometer to test the humidity in the air if its too dry you may get a Boron deficiency.

Issue: Spotting/ mottling, dead spots, crinkling, stunned growth, curled tips, small or poorly formed new leaves, leaf die off, weak stems, weak or unhealthy roots.

This is a Calcium deficiency will show up in parts of the fan leaves that have been exposed to light or the newer growth.

Solution: Make sure your pH is correct after the calcium issue is corrected the damaged leaves will not return to normal but the new growth will show the correction. Cannabis plants usually can handle a high calcium add General organics Cal-Mg or Botanicare Cal-Mag Plus. You can also use Dolomite Lime it can be mixed into your soil add 6-7 teaspoons to one gallon of soil. You can also add crushed egg shells for another organic alternative.

Issue: Tips of leaves turn bright yellow or white, leaves turn dark with blue or yellow undertones, shiny or metallic sheen on leaves, Buds don’t ripen or mature very slowly, leaves feel stiff and bent under, wilting or drooping.

This is a Copper deficiency its usually from a pH issue so make sure that is correct and use the right nutrients and is also when the grower uses RO (Reverse Osmosis) water because that filtering process strips out some Copper. It also will happen if a plant is being over watered.

Solution: Don’t over water your plant and make sure the pH is at the right level. Use quality soil and nutrients made for Cannabis.

Issue: Newest leaves turn completely yellow and white. Usually shows in the center and outward on the leaves. Pale colored leaves, Slow growth, Buds not maturing.

This is usually a Iron Deficiency a solution:  Make sure your pH is correct feed with a nutrient containing iron, calcium, and magnesium.

Issue: Light green or yellow will show on the veins or edges of the leaves they may also be crisp to the touch. It usually appears on the lower part of the plant because the plant will pull Magnesium from the lower leaves.

This is Magnesium Deficiency and a solution: It can be treated by feeding a Magnesium supplement like Cal- Mg as mentioned above. Also again keeping the pH in check is a big importance.

Issue: Leaves turn yellow between vein areas and have brown mottled spots. The brown spots eventually spread and kill the leaf they may also shred and crumble apart. The yellowing will begin at the base of the leaf and move outward, overall plant growth is slow.

This is a Manganese deficiency  and a solution is to flush out the medium using pH’d water and a light nutrient that contains Manganese will correct this.

Issue: Pale and yellow leaves, brown an dark spots, Pink coloring and yellow, red around edges of leaves.

This is rare but it is molybdenum deficiency and a solution is to completely flush the plant and then add a nutrient that includes molybdenum and make sure the pH is set.

Issue: Edges appear brown on tips or dark leaves, dark patches on leaves, leaves will turn under and crack off.

This is Nutrient Burn and a solution is to completely flush the medium out with pH’d water use a flushing solution like Foxfarm sledgehammer Bushdoctor or flush with plain water.

Issue: Yellowing appears starting at tips of leaves and works inward then leaves will turn grey or brown and die off. They will also curl down and the stems will turn bright red or purplish.

This is Phosphorus deficiency a solution is to feed with a high phosphorus nutrient and adjust the pH Phosphorus is best absorbed by cannabis in soil at a root pH of 6.2 – 7.0. Phosphorus is best absorbed by cannabis in hydro at a root pH of 5.5 – 6.2. too wet or compact soil can trigger Phosphorus deficiency. Too low temperatures under 60 degrees Fahrenheit can also trigger it. Good sources of Phosphorus are: Bat Guano, Bone or Blood meal, Worm Castings or Worm tea, Fish meal, Bloom or Flowering nutrients. Make sure you make the Bat Guano and Bone/Blood Meal into a tea before applying it to the plant.

Issue: Leaves appear burnt or brown on edges and show yellowing or paleness, veins of leaves stay green, Brown or dark spots, Lower leaves affected.

This is a Potassium Deficiency a solution is again to flush the medium and feed with a potassium nutrient. Its also due to stressful conditions like heat, over watering, transplanting. Make sure the pH is correct when feeding and watering to assure proper uptake of nutrients.

Issue: Pale colored leaves, yellow leaves in new and old growth, yellowing between veins, red or pink color on stems, Buds not maturing properly.

This is Sulfur Deficiency and a solution is to check your pH to make sure sulfur isn’t being locked out.

Lastly is a Zinc Deficiency same with other issues pale leaves and spotting. A solution is to adjust the pH and make sure you feed with a balanced nutrient. Zinc deficiency is likely to appear when using RO water due to it being stripped from the water during the filtration process.

As with most of the issues pH is a important factor and feeding a well balanced line of nutrients to the plant. Also to prevent over feeding or nutrient burn its important to flush out ever 2 -3 weeks. Make sure your giving the plants good amounts of water without over watering. Humidity should be correct also to prevent issues. Daily care and spotting issues early is important for them to reach maximum potential.

Feeding Cannabis

When growing Cannabis it is important to feed it properly.
In vegetative it gets different types and amounts of nutrients then when in flowering. PH is also a important factor when giving nutrients because it will allow the plant to take up the nutrients properly when the PH is adjusted. NPK is the three main nutrients the plant will need during the growing cycle. These fit in the category macro nutrients.

Nitrogen (N) – Helps plants make the proteins they need to grow more tissue

Phosphorus (P) – Helps root growth and helps the plant bloom and flower. It improves plant strength also helps seeds grow bigger.

Potassium (K) – Helps all the functions of the plant to produce correctly.

When looking at a fertilizers content the three numbers show the amount inside the fertilizer so 10-10-10 is a even amount of all three nutrients. Each number is a percentage of what is in the nutrient mix so 10-20-10 would be 10% Nitrogen, 20% Phosphorus, and 10% Potassium. When Cannabis is in the vegetative stage it requires more nitrogen to form more leaves and grow quicker. While in Flowering (budding) stage it requires more Phosphorus.

Other nutrients are also required for better results some are below.

Calcium (Ca) –  Helps with heat stress and also the structure of the plant and leaves. Calcium deficiency will show in the leaves they will be dull in color starting on the ends also will show as brown spots or yellow. It usually appears in the fan leaves that are under the lights or it will show on new growth. Dolomite Lime  is a great calcium magnesium supplement add 6-7 teaspoons of fine dolomite lime to each gallon of soil. I also use CaMg+ from General Organics when I feed Calcium. Other signs of Calcium Deficiency are Crinkling, Spotting, mottling, small brown spots, small or stunned new leaves, curled tips, leafs die – off, dead spots, weak or brittle stems, Slow bud or leaf development. You can also get calcium from finely crushed egg shells.

Magnesium (Mg) – Is needed for photosynthesis its a part of the chlorophyll in all plants and helps activate the plants enzymes needed for growth.

Sulfur (S) – Has many uses in the plants growth one is that its essential for the production of proteins. It also improves root growth and seed production. Aids in the formation of chlorophyll and faster plant growth. helps protect plant in cold temperatures.

Next are the micro nutrients:

Boron (B) – Helps in the use and regulates nutrients also aids in the production of sugars and carbohydrates, aids in seed and fruit development.

Copper (Cu) – Helps in the utilization of proteins and aids in root metabolism. 

Chloride (Cl) – Aids in plant metabolism.

Iron (Fe) – Helps with formation of chlorophyll.

Manganese (Mn) – Involved in the aid of break down of carbohydrates and nitrogen metabolism.

Molybdenum (Mo) – Helps with the use of nitrogen.

Zinc (Zn) – Essential in the transformation of carbohydrates, regulates consumption of sugars part of the enzyme system that regulates the plants growth.

If a plant receives all the required nutrients it will produce better results and yield its important to not over feed but to give the plant what it needs in weekly doses and to also flush out excess built up nutrients every 2-3 weeks. All nutrients have a feeding schedule usually the manufacturer will have a feeding schedule that shows how much and when to use the nutrients. Read the label and follow how much it tells you to use per feeding each brand is different. Ruderalis Cannabis usually is half the recommended dose so be sure to only use half strength for the Dwarf auto flowering varieties. Keep your PH levels 6.5 for soil and ideally 5.7 for hydroponics but they can handle a range of 5.6-6.2 so be sure to measure that before you feed the plants so they can uptake all the nutrients. If you have any questions feel free to contact me thank you for reading hope you enjoy my blog.

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