Nutrient disorders and their related effects

Originally posted by Cannabis Connosseur.

This is intended to be a beginners guide to nutrient disorders and their related effects on the MJ plant.

One of the most common questions asked is “What’s wrong with my plant?” We hope that this will serve as a guide to “help” diagnose any potential problems.

Be sure about your decision before you do any radical changes to your feeding schedule or composition. This is only a helping hand towards a solution and hopefully a way to help avoid potential problems…this is not a Nutrient bible!


Nutrient disorders and their related effects.



First, we should start with the basics. There are two groups of nutrients that the MJ plant uses: the Macro nutrients and the Micro nutrients.

The Macro nutrients are what all growers should watch carefully. These are the Nitrogen (N), Phosphorus (P) and Potassium (K) levels that are fed to the plant. Too much or too little of this group (individually or as a whole), and you will damage your plant, possibly kill it. The common method of tracking and recording your N-P-K levels is in ratio form. For example, a good vegetative NPK ratio is 10 - 7- 7(which would be the same as 20 –14 -14 or 5 - 3.5 - 3.5) and a good flower ratio is 1-2-2. All MJ plants have specific nutrient needs…so each one will thrive with a unique NPK ratio. Most nutrient companies state the NPK ratios of their feeding systems, so look for something that will closely match the needs of the MJ plant. Each Macro nutrient and its effects, or lack there of, will be discussed below.

The Micro nutrients are the group of nutrients that the plant does not take up in as large a quantity (like the NPK’s), but still play an important role in the growth of the plant. There are several and they will also be discussed below, but some primary examples include Iron (Fe) and Magnesium (Mg).



This is what your plant eats:

Boron – In solution, a plant consumes very little B during its life. A Boron deficient plant will develop curled or twisted leaves that turn brown or die. Boron deficiency is extremely rare, MJ plants require very little B. Some growers are experimenting with enhanced Boron environments (forced Boron intake through foliar feeding by Boron gas)

Calcium – Ca is an important Micro nutrient that MJ plants require. A Calcium deficient plant (rare) is often shown by twisted or curled leaves and brown spots that can spread rapidly. Too much Ca can be lethal to your plant though. Potassium (K) and Magnesium (Mg) can be “locked out” if the Calcium levels are too high. Watch your tap water…”hard water” (tap water in most North American cities) is generally Calcium rich. If your faucet heads have mineral build up on them, your water is not recommended for MJ growing…too many unknown minerals (usually a lot of Calcium) in the water.

Copper – Cu starts to get locked out when the pH level goes over 7.5. Many of the Micro’s get locked out when the pH rises beyond 7.5, in soil/soil-less or hydro. Cu deficiency usually shows itself as a wilting plant…even though all other variables are within normal levels.

DTPA – DTPA is the commercial name for chelated Zinc. Zinc that is “chelated” has been processed to give it maximum availability to the plant roots.

EDTA - EDTA is the commercial name for chelated Iron (a micro nutrient). Iron that is “chelated” has been processed to give it maximum availability to the plant roots.

Iron – Iron (or EDTA) can be locked out if the pH goes too high. Iron deficiency can show itself as slow growth combined with yellowing, almost whitening leaves. If your pH level is kept below 7, you should never experience Iron deficiency. If there is too much Phosphorus (P) present in the roots then Fe will be locked out. If you do suspect a low Iron level, lower you pH to about 6.3 – 6.5 until normal growth resumes. An excess of Iron (usually caused by too low a pH), will lock out Potassium, Manganese and Nitrogen.

Manganese – A micro nutrient that can be locked out at high pH levels or when the Iron (EDTA) content is too high. This is another problem that can be easily avoided by watching your solution pH levels. A lack of Mn can be seen in plants that are yellowing/ browning at the base of the leaf rather than the tips of the leaves.

Magnesium – Mg deficiency is common amongst indoor MJ grows…especially in soil. Most soils and some hydro solutions do not contain the proper levels of Magnesium for MJ to thrive. Magnesium will be locked out if the levels of the Ammonium, Calcium or Chlorine get too high. Mg deficiency can be seen as yellow spots that gradually spread (as a yellowing) and consume the leaf, but the leaf border stays somewhat green and is turned upwards. Too much Mg will lock out a lot of other nutrients, so raise Magnesium levels gradually and carefully watch the results. You can raise the Magnesium level by adding finely powdered Epsom salts to your solution. If you suspect that the Mg levels are too high, flush your system with clean water for a while and observe the changes.

Nitrates – This is the Chemist’s name for soluble Nitrogen. Nitrogen that is suspended in a solution is more “readily available” to the root system. Most hydro growers are using Nitrates to feed their plants the Nitrogen it requires.

Nitrogen – A lack of Nitrogen is easy to spot; the plants yellow in an almost uniform manner. A plant short on Nitrogen is obviously “paler” than a plant that has an ample supply of N. The reason is because the plant is “pulling” N from the leaves to supply what it is not getting from you. For soil or hydro, slowly (over the course of 5-7 days) add fish emulsion (in solution) to raise the level of Nitrogen. If N levels are too high you will burn your plant and this will result in leaf tips going brown; this will spread until it dies unless a proper flush is done, If the Nitrogen levels get too high your plant might develop a weak stalk and stems. You want the Nitrogen levels high (not too high) during the vegetative portion of the growth cycle, but you should starve your plant of N during the final two or three weeks. This “starving” promotes a better and more natural tasting product.

Phosphorus –Do not over feed the Phosphorus during the late stages of flowering (last four weeks) or you will hurt bud development. Too much P will also lock out Iron and some of the other Micro nutrients. All MJ plants crave more P during the late stages of flowering. Some P starvation is acceptable, if not the norm. Phosphorus deficiency tends to shows itself with a wide variety of symptoms and, therefore, is quite hard to accurately diagnose. Some of the symptoms include yellow tips on new growth, full grown leaves curling under and turning yellow (in that order), and some growers say that plants that are a very dark green may have a P deficiency.

Potassium – K deficiency is serious. It starts as yellowing patches that turn brown, then die and slowly consume the leaf. If the Ammonium, Calcium or Sodium (salt) levels raise too high, Potassium will be locked out. If the temperature drops below 50 degrees F, P can be locked out and it shows itself as the “purpling” of the bud tips and possibly leaves. Salts are sometimes (Sodium Bicarbonate) used to raise the pH level of a solution and this can lead to a K lock. Hydro growers need to carefully watch the salt build-up on their reservoirs and baskets (LICA balls and rockwool too).

Zinc – Zn (DTPA) deficiency is quite rare, though it does happen. A Zinc problem can usually be fixed by lowering the pH level a bit to alter the speed at which your plant is absorbing Zn. Again, most of the Micro’s get locked out in a high pH environment…so, keep you pH under 7 to avoid these problems. A Zinc problem has leaves that are yellowing/browning at the base rather than the tip, but the leaves are also twisting themselves around.


After spending about twenty hours putting all the information together for this guide (search after endless search), I have come to a simple conclusion:

***Watch your pH levels closely***

Most nutrient disorders can be avoided by keeping your pH between 5.8 (as a C.C. minimum for safe growing) and a C.C. maximum of 6.8. If you keep an eye on your plants closely (sometimes a luxury), they will always tell you what they want or don’t want. They can speak...we just need to learn their language

Good Growing …

bum bum bum bump

In my experiences- I have found that whether your plant shows signs of a deficiency OR a toxicity, a good, easy way to nurse them back to health (if possible) is to give them a "bath." By this, I mean that:

If you are growing in soil- you would flush their pots by pouring water into their soil & allow it to run out the bottom (you should make the amount of water 2-3 times as much as the pot can hold.) This will remove any salt (sodium bicarbonate) build-up from the soil (which could also have been the problem) and give you a "clean slate" of soil to work with. Then mix some new nutrients at around 35% of the suggested ratios (what the label says), balance the pH to around 7 (within .2 either way) and add a vitamin B supplement (like Super Thrive) at .5 ml. per Gallon. Now pour some of the nutrients around the outer edges of the pots after flushing (when the "flush" water is no longer dripping out of the bottom), until the nutrients begin to drip from the bottom. Now the plants are have good pH balanced soil, with nutrients strong enough to fix a deficiency but weak enough to bring a toxicity back down; the plants should show improvement within a couple days (note: brown, "rusty" or necrotic spots will never heal.)

If you are growing in hydroponics you would dump your nutrient solution. Then clean out your equipment with a light peroxide or bleach solution diluted in water (like1 cap full per Gallon.) Afterwards, run the plants on almost pure water (like 1 ml. per gallon of micro, grow & bloom, pH balanced around 6), because taking ALL of their nutrients away at once could possibly shock them. Run the plants this way for about 12 hours and then increase the nutrient solution concentration to 30-40% of the suggested ratios (pH'd around 6) for a few days, until the plants show improvement. Then you can gradually increase the nutrient concentration to your desired ratios.

This is assuming that the plants are not root-bound, the nutrients being used are compatible with Cannabis, there are no pest problems or disease and that the environment is acceptable for growth (adequate lights,ventilation, temp./humidity, light cycles, etc.) The amounts of light, nutrients, water, etc. should be relative to each other (i.e.: if you have a low-powered light, you would want to use less nutrients.) Some nutrient problems are very rare and like mogie said- keep an eye on your plants, most of these problems are caused by pH imbalances... I set mine at 5.7 and let it rise naturally to 6.5 (the pH in a healthy hydro system will tend to rise when buffers aren't used.)

I'm not telling anyone to do anything, this is just what I do and it has always worked for me.