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.

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