Guide to Nutrient Deficiency or Toxicity


Well-Known Member
So 99% of the times I come in here to see what people are up to and check what forum threads I can throw some advice in, its plant issues.

"theres yellowing" or "leaf is dry and brittle" or "OMG SPOTS!"

so instead of using the 'cut and paste' tools, over and over all day, like I feel I have been, i figured id start this. Theres other stickies on here, but apparently people either dont read them, or cant connect their plant's issues to what those authors are describing.

*NOTE: to make sure your plant is getting what it needs, keep soil pH to 6.5 and 5.8 in hydro, otherwise, the nutes can be there, but the roots cant take them in*

Also, make sure if you notice a deficiency, please please PLEASE, dont drown the plant in that chem to save the day. your not superman. feed the plant. dont suffocate it! Slow changes are the best way to make sure you dont go from a deficiency to an abundance, and the inevitable burn.

So lets start with the basics, NPK.

Nitrogen: This element is everywhere, your breathing it in right now! For your :leaf: plants, its key in the vegetative growth. It stimulates and powers the formation of leaves, strengthens the stems, and helps the chlorophyll production.

An abundance of this is rare during vegetative, but it happens with new growers that think more ferts = more plant (and your right, but to a limit!). To tell if you have an abundance of nitrogen, simply look at the plant. You want green leaves, but not a dark green -> black color.

A deficiency of this causes yellowing of the leaves. its common during vegetative simply because the plant is using it up just as fast as your putting it in. It also happens during flowering sometimes because most flowering fertilizers contain little or no nitrogen, as this is not a key nutrient in that phase of the plant's life cycle.
Usually the deficiency will be noticeable on the lower part of the plant, on the older leaves. then, as it progresses it will move upwards towards the newer growth.
*unlike a magnesium deficiency, nitrogen def will start from the tips and works its way inward* (ill get to mag def later). Most of all yellowing of leaves is caused by this, and it will stunt growth severely!
View attachment 1894154

Phosphorus (P):
The 2nd element in our NPK ratio and just as important! So, whats it do? Root growth. This nutrient is essential for the roots to thrive, and big roots can feed big plants. Its key from the time the seed hits the dirt. it speeds up germinating, it supports vegetative growth by providing the roots to support it. Its a MAJOR nutrient in reproductive stages of the plant (yes, flowering). No phosphorus, no buds.

Abundance: too much can affect plant growth by suppressing the intake of iron, potassium, copper and zinc. (wierd huh? but yea, phosphorus abundance is generally followed by a zinc deficiency)

[if someone has a pic of P abundance lemme know and ill add it in]

Deficiency: Didnt i go over this? slow growth! slow leaf growth, slow root growth, slow germination of seeds, slow bud production, the edges of eaves will be brown. Even fan leaves, the plants solar cells, will be affected by this, turning them to a dark green, purple and blue color. (not the kind of purple you want.)
*Deficiency of this can be caused by low temperatures - below 50F/10C

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Potassium (K):
a.k.a. potash, this nutrient is key for the usage of carbs/sugars. This is key for sturdy/thick stems, small bushy plants and disease resistance. Its needed for all stages of plant growth, especially bud formation.

Abundance: this is pretty rare to notice, excess potassium usually isnt absorbed by the plants but can mess with levels of magnesium, manganese zinc and iron. This in turn leads to salt damage acid fluctuations and possibly a calcium deficiency

Deficiency: this has yellowing of leaves, from outside in, but with a dark green center vein, and curling of leaf tips, this is mistakenly diagnosed as nitrogen def or iron def a LOT. Stems and branches will be weak, easily broken. the plant may also stretch. *too much sodium (NA) can cause a potassium deficiency.

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Ok so thats the basics. Now on to the trace elements. Wonder why they call them 'trace' elements? and why you dont see ratios or percentages on how much of them to use? its becuase you dont want too much of them. you want them, but very very little.

Magnesium (Mg): this is a component of the chlorophyll molecule, it works with enzymes in the plant. Magnesium helps support healthy veins, and leaf production.

Abundance: Excessive levels will create a toxic amount of salts, that will inturn kill your leaves, and lock out calcium.

Deficiency: This is pretty easy to notice, green veins but fully yellow leaves. leaf tips can discolor and curl upwards. leaf edges can feel dry and crispy. the necrosis on the leaf will start at the edges, work all the way around the leaf. the tips will twist and turn, then the leaves will fall off without withering. *mag def is common with too acidic pH*
heres 3 pics of early-med-late deficiencies of magnesium:

View attachment 1894202

mag_def_middle.jpgView attachment 1894204

Zinc (Zn): Zinc does a little of everything, helps in plant size production of leaves, stalks, stems branches... Essential component in enzymes and growth hormones. its key in the formation of chlorophyll. Plants that have a healthy amount of zinc are more resistant to drought.

Abundance: this is rare. it can cuase wilting and death in extreme cases. but usually, this wont happen.

Deficiency: Spotting, bleaching of spots between veins (commonly confused with iron/mag def). Usually appears on older leaves first. It will affect the tips of growing points on the plants. Small crops due to zinc def is common. Pale/greyish leaves will be apparent (check for a nice shine to the leaves, if they lack some luster, they might lack zinc!)

View attachment 1894207View attachment 1894209

Calcium (Ca): Strong bones, duh. no really. strong cell walls, cell division, and root growth (mostly the newer root hairs). Helps absorbtion of K. Calcium moves slow, and tends to concentrate in roots/older growth.

Abundance: Too much can lead to other deficiencies. this can be caused by clay soils, unbuffered coco/humus, or excessive lime in the soil.

Deficiency: First visible in newer growth, leaf tips will die, tips may curl, growth is stunted. there will be a weakness in stems/branches. underdeveloped roots, and bacteria problems can arise. *can be cuased by too much potassium/nitrogen* calcium deficiency is commonly mistaken for over ferting. its key to notice in these pics that early stages of deficiency appear in the serrated edges/tips of the leaves, but its not just a death/necrosis, its a small circular spots of death, not just burn marks. young leaves will develop dwarfing, a strap-like shape, and shoots stop growing and thicken.
View attachment 1894224

later, it appears all over the leaf, and becuase its usually on the older growth, many people think its bugs. (noobs.... do you see bugs anywhere?)
View attachment 1894226

Iron (Fe):
Abundance: This is mistaken a lot for pH imbalance. Brown spotting on top leaves. can affect the entire plant. This is rare with pH below 5.5

Deficiency: discoloring of the leaves mainly between the veins, starting with the lower/middle leaves. when i say discoloring, i dont mean a light green, i mean almost white. its a bleaching that starts at the top, and moves down, eventually, necrotic spots appear. this can be caused by over watering, excessive salts,
View attachment 1894241

Sulfur (S): important in root growth

Abundance: plants will be small even tho the leaves continue to be relatively large. the leaf tips will be brown and dead. this is commonly confused with salt damage.

Deficiency: the first sign will be pale new leaves. growth will be stunted. leaves can be brittle and narrow-er then normal. you can get mutated leaves becuase of this. in flowering, buds will die off! NOT COOL. stems will become hard and thin. this is commonly confused with nitrogen deficiency, but NO, the yellowing starts at the center of leaf, and works its way outward. (pic 1), then 2nd pic shows mutations caused by S def.
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Manganese (Mn): this aids in chlorophyl production and enzyme usage.
Abundance: too much will cause an iron deficiency. blotchy leaf tissue. plants will seems to have weak vigor.

Deficiency: Young leaves will be mottled, spotted with yellow and brown areas. dead spots will appear, leaves will yellow, veins remain green. rumored that leaves can have a checkered pattern. This really only happens in young/new growth.
View attachment 1894258

Boron (B): this is key for pollen/seed production, and absorption of calcium.
Abundance: too much boron can produce a lot of problems. leaf tips turn yellow progressing inwards. this is commonly confused with a mag def, but only on new growth.

Deficiency: this will first show on younger leaves, they will yellow. this resembles calcium deficiency. stunted growth, discoloration, death of growing tips. buds will stop forming. tip of shoots will die. stems/petioles will brittle. leaves will curl, and die. dead spots develop between veins, and leaves will become thick. boron is not absorbed with too much potassium. a lack of boron can lead to rot/fungus. can also cause severly hollowed stems. (fast fact: boric acid can be purchased at pharmacies for fungus treatment, as well as for jewelers to remove salts/oils from their work before they apply the torch to them. its kills bacteria, and can even be used in your laundry as a weak bleach!... the more you know....)
View attachment 1894276

Molybdenum (Mo): helps the plants absorb nitrogen from the air.

Abundance: this generally doesnt cause any issues....until you smoke it. ( /cough cough, puke puke). abundance will appear as iron/copper deficiencies.

Deficiency: leaves will pale, appear fringed and scorched. wierd leaf patterns. Yellowing of middle leaves. twisted younger leaves. this is commonly mistaken for a N deficiency, generally starts on older growth, and moves to newer growth. this usually happens when sulfur and phosphorus are deficient. Severe Mo def will appear as pinkness/orange color to leaves.
View attachment 1894279

these last few ill be quick on, they arent very common at all, except maybe the chlorine one, but dont use freshly poured tap water, and you wont you have issues with it.

deficiency: sturned growth, distortion of younger leaves. twisting.
abundance: root growth stops.

Cobalt: essential to bacteria in soil. abundance is rare (shits not cheap so many nutes wont have it) and deficiency wont occur (becuase the plants dont need it, the bacteria in the soil can use it, but dont require it either)

Chlorine: FOUND IN WATER FROM THE TAP, ironically, it evaporates at lower temperatures than water, so pour a large jug, leave it out for 1-3 days, and its chlorine free. Deficiency: leaves will appear bronze. roots stop growing. Abundance: burnt leaf tips.

nickel: much of this isnt known/documented in detail, but its rare to have issues with it. mainly its used for seed germination, but most soils have plenty, and more wont be needed for the duration of the grow.

So, to sum this all up: death of leafs, discoloration, twisting, etc... is usually a deficiency. If the issue started with just the tips, make sure its not your calcium being off, otherwise, its probably nute burn. (the majority of the times, the nutrients will accumulate in those serrated edges/tips, they act like little buckets, and they burn). thats the first sign you put too much crap in.

If you see an issue on your plants, dont freak out! if you think you didnt put enough of something, water the plants, with the nutrient mixed in, AT A LOW DOSAGE to start. if it gets better, you were right. if it doesnt, you werent, but atleast ya didnt cause an abundance of something else.

If you think you put too much of something in, then you have 2 options, if its just some burning on the leaf tips, dont flush it out with gallons of water, as this isnt good either. just water a little (with 0 of the excess element), and with time, the nutrients will balance out again. if you accidently tripped over the power cord to the lights, and dumped a gallon of some nutrient rich solution onto a plant, then yea, flushing might be smart.

If your in soil, and you have the catch trays, RINSE THEM OUT EVERY SO OFTEN. nutrients in the runoff will accumulate. if your in a hydro set up, CLEAN THAT OUT TOO. as the water in the reservoir dries, the nutrient will cake up and dry on the sides like a crusty salt build up, and when you add water next time that stuff will mix in, and something will get all crazy.

the key is to check the plants often. dont freak out when theres an issue. and keep a tidy grow room. you dont want bottles spilling all over the place, or mixtures on the counter being unmarked and you guessing at what they are.

the last piece of info i can give: You are not a genius or a godlike deity. dont think you can take a turd in the backyard, wait a week and use that as home made fertilizer (yes, theres a thread on this.) the entire point of this websites' forums is a community of people, knowledge, and experience. trust Roll it up. trust each other and trust yourself.

happy growing!


Well-Known Member
Ty guy NICK ...(I think my prb is Ca def so)IMGP1882.jpgIMGP1884.jpgIMGP1893.jpg
U r perfect doctor for us..
Wish to hear more and more from u and your exp/////
Very very good issue....
BEst wishes ....


Well-Known Member


Weed Modifier
this material is provided everywhere on RIU.... but I do see your point.

some just want an answer without doing any research, but when it comes to growing it can be Very simple ( with a little knowledge of the basics ) and this comes from reading,reading,reading and experience. :bigjoint:


Good post +rep


This is a really awesome post. So many threads give detailed descriptions on deficiencies but not on over nutrients. +Rep.


Well-Known Member
yea thanks for the responses guys! its hard to find pics of abundances of chems, so if you guys come across them, send them to me and ill edit that post.
Happy growing!


Very helpful feed. So I am 99% sure I have a calcium problem. My leaves look almost identical to the bottom photo under calcium. Whether its an abundance or deficiency, I am not sure. My plants are well into the flowering stage and Ive been giving them steady pottash fert. Which makes me believe it might be a calcium deficiency. However I had used organic soil with hummus in it which is stated in calcium abundance. But my real question is, How do I fix a calcium deficiency? And if its an do I correct it?


Active Member
Great info well done. I don't want you to feel it was in vain, but even as a sticky it will get overlooked. That's the nature of the beast with forums.

Plus rep for effort


I find it gives little consideration to most using a two part fertilizer where simply adding more A or B so to say will cure most problems. Most two part fertilizers are pretty complete for the competent grower and it should be easy to work out your Cal/Mag levels too so i find a lot of this merely confuses the grower more over just learning to use his ferts properly and checking Cal/Mag levels.

Some ask whats this deficiency and the answer is not necessary Phosphorous or Calcium over add more A or B to vary the nutrient levels. Lots of blooms or B dont contain enough nutrients to make it complete hence why most nutrient companies advise on their chart to run veg ferts through the flowering but simply upping the bloom ferts till the P/K is higher than the N. Without the grow yer you probably are Cal or Mag deficient not to mention the abuse of Phosphorous and Potassium. Thanks


Well-Known Member
Great info well done. I don't want you to feel it was in vain, but even as a sticky it will get overlooked. That's the nature of the beast with forums.

Plus rep for effort
yea im sure it will be overlooked, but for those that read the forums before starting new threads (such a novel idea), this is another reference.

Im dealing with bugs at the moment in my personal grow, maybe ill write something up on that, still trying to figure out the best ways to deal with it. im trying dif techniques on each plant, and seeing which work best.
Either way, plants will grow. people will read or not read forums. hopefully this just gives us another tool in the battle for bigger better buds.