Nitrogen deficiency(?) outdoor/soil, early flower

First off I’d like so say thanks in advance to any insight/suggestions the guru’s and experts here can provide.

Based on what I’ve read I’m 99% percent sure I have an N deficiency as the title of this post would suggest. (Older fan leaves yellowing at the bottom of the plant, with a few starting to pop up mid plant. They are outdoor in soil between weeks 2 and 3 of flower)

If I am correct in my assessment, what is the best way to remedy the problem? (add N, duh!)

I picked up some Home & Gardens N boost [] at my local nursery and started with 1/4 of the dosage (1ml or about 1/4 teaspoon per gallon of water) w/ half of the recommended bloom nutes. Been running that for about a week, no change. Leaves continue to yellow and die and on a few of my ladies I noticed a yellow leaf or two creeping up mid plant or slightly above. The rest of the plant(s) looks great.

From what I understand this isn’t that common in outdoor grows and I have never had this problem before. I can only surmise that it possibly came from me introducing bloom nutes too early in flower (idiot!) and not continuing to give them grow nutes.

So, what would you guys suggest to remedy the problem? I still have some granular grow ferts that I could give them. Or should I increase the N supplement? Or go another route?

(pic 1 how it starts, pic 2 progression, pic 3 death to the yellow leaves)

might be nutrient lock? What is your Ph?


First I would like to welcome you to ILGM

This is a pic of what I believe it to be. OK

Nitrogen (N) Mobile Element and Macro Element

Benefit: Nitrogen plays a very big role in your plants; this one element is directly responsible for production of chlorophyll, photosynthesis, Amino Acids, which are the building block of Proteins. The myriad of enzymes which help the plants growth in leaves stems and the how well the vigor of your plants is.

Nitrogen is the biggest mobile element meaning it can travel anywhere on the plant.
Usually the def will start on the lower to middle part of the plant, and then will usually happen to older leaves first. Then the deficiency will work its way up the plant. Your plant can be green on top, then yellowing on the lower leaves when the deficiency is starting out. Yield will be greatly reduced without good amounts of nitrogen in your plants. Sometimes in bad cases the leaves will turn a purplish color along with the yellowing.

Unlike a magnesium deficiency, nitrogen def will start from the tips and work its way back to the leaf node. Nitrogen and Magnesium get confused. The best way to tell them apart is, nitrogen deficiency starts around the tips and works its way to the back of the leaves, where a magnesium deficiency will cover the entire outer part of the leave and make the entire leaves yellow leaving the veins to stay green. If your plants are having a slow growth rate and have yellowing of the leaves, then most likely it’s a nitrogen deficiency.
Towards the middle to end of flowering stages, the plant will show a nitrogen deficiency almost always. This process is completely normal and just let the plant naturally yellow out as it uses it’s stored nutrients. This actually helps you by getting ready for final flushing and then harvesting. At this point DO NOT not use nitrogen to fix the problem. The yellowing leaves will then eventually drop off after the plant is done with them.

Parts affected by a nitrogen deficiency are: Older foliage, going to whole plant, Petioles (rare) cases.

Now for having too much nitrogen in your growing mediums or soil. The plant will have like an overall DARK green look and have delayed maturity. Due to Nitrogen being involved in vegetative growth, to much nitrogen will result in tall plants with weak stems. New growth will be very lively and plant transpiration will be high, but not always. Nitrogen toxicity can be seen when there are very very dry conditions almost as if there was a drought, which may show a burning effect. If you give your plants ammonium based nutrients they may show NH4+ toxicity, which will show a smaller plant growth and lesions that occur on stems and roots, leaf margins that will roll downward. Also the big fan leaves will have “the claw” look. The tips will point down but the leaves will stay up as if when you bend your fingers downwards. Leaves can be twisted when growing… mainly new growths. Roots will be under developed along with the slowing of flowering. Yields will be decreased, because to much nitrogen in early stages of flowering slows down bud growth. Water uptake is slowing down from the vascular breakdown of the plants as well. Too much potassium and nitrogen will lock out calcium as well.

Problems with Nitrogen being locked out by PH troubles.
Waterlogged soil and Soil with low organic matter.

Nitrogen is a very important element in the plant, all of them are but some are more important than others. For soil the best ph to have is 6.8. Why? Because at 6.8, that’s the best number for ALL available nutrients to be absorbed into the plant without any of them being locked out. For hydro and soil less mediums best ph to have is around 5.8.
Try not to keep your plants to cold, because the cold temps will cause the nitrogen harder for the plant to be absorbed.

PH levels for Nitrogen:

Soil levels
Nitrogen gets locked out of soil growing at ph levels of 4.0- 5.5.
Nitrogen is absorbed best in soil at a ph level of 6.0-8.0. ( wouldn’t recommend having a ph of over 7.0 in soil) best range to have nitrogen is a ph of 6-7. Anything out of that range will contribute to a nitrogen def.

Hydro and Soil less Mediums
Nitrogen gets locked out of Hydro, Soil less mediums at the levels of 4.5-5.0.
Nitrogen has the best absorption rate at a ph of 5.5 to 8.0
(Wouldn’t recommend having a ph over 6.5 in hydro and soil less mediums.) Best range to have Nitrogen is: 5.0-7.0. Anything out of that range will contribute to a nitrogen def.

Solution to fixing a Nitrogen deficiency

Avoid excessive ammonium nitrogen, which can interfere with other nutrients. Too much N delays flowering. Plants should be allowed to become N-deficient late in flowering for best flavor.
A goof solid N-P-K ratio will fix any nitrogen deficiency. Any chemical or organic fertilizers that have Nitrogen in them will fix a nitrogen deficiency., Peters all purpose plant food 20-20-20 is good, Miracle grow All purpose plant food, Miracle grow Tomato plant food, (Only mixing at ½ strength when using chemical nutrients, or it will cause nutrient burn!) as well and blood meal! If you need to give your plants a quick solution to nitrogen and you want to use blood meal, I suggest making it into a tea for faster use, where blood meal is slow acting, but when made into a tea it works quicker! Other sources of nitrogen are dried blood, Cotton seed meal which is slow acting, Insect eating bat guano which is fast acting. Bone meal which is a gradual absorption when not made into a tea.( also excellent source of phosphorus). Fish Meal Or Fish Emulsion is a good source of nitrogen and is medium acting. Worm castings, which is gradual absorption. Seabird guano, All purpose Millennia Seabird guano, Orginal Seabird guano All Purpose, Crabshell ,which is slow absorption. Fox Farm Grow Big, which is fast acting. ( can bring down your ph as well)
Here are a list of things that help fix a Nitrogen Deficiency:

Chemical Nutrients

Advanced nutrients Grow (2-1-6)
Vita Grow (4-0-0),
BC Grow(1.2-3.2-6.5)
GH Flora Grow (2-1-6)
GH Maxi grow (10-5-14)
GH floraNova grow (7-4-10),
Dyna gro Grow (7-9-5)

Organic Nutrients

Dr. Hornby’s Iguana Juice Grow (3-1-3)
Advanced Nutrients Mother Earth Grow (1.5-.75-1.5)
Earthjuice Grow (2-1-1),
Pure Blend Pro (3-1.5-4)
Bone Meal(0-10-0)
Blood Meal(12-0-0)
Fish Emulsion (5-1-1)
Seabird Guano (11-13-3)
Crab Shells(2.5-3.0-.5)
Pure Blend Grow (0.4-.01-.5)
Marine Cuisine (10-7-7)
MaxiCrop Seaweed (1-0-3)
Super Tea (5-5-1)
Mexican Bat Guano (10-2-0)
Sea Island Jamaican Bat Guano (1-10-0)
Kelp Meal (1-0-2)
Seaweed Plus Iron
Neptune’s Harvest (2-4-0.5)
Alaska Start-Up(2-1-2)
Bio-Grow (1.8-0.1-6.6)
Age old Grow (12-6-6)
AGE Old Kelp (.30-.25-.15)
Neptune’s Harvest (2-4-1)
Maxicrop Seweed(.1-0-1)
METANATURALS Organic grow (3-3-3)
METANATURALS Organic nitrogen (16-0-0)

So adding anyone of these above should fix up your nitrogen deficiency! Nitrogen deficient plants usually recover in about a week, affected leaves will not recover.

Now if you added to much chemical nutrients and or organics, (which is hard to burn your plants when using organics) you need to flush the soil with plain water. You need to use 2 times as much water as the size of the pot, for example: If you have a 5 gallon pot and need to flush it, you need to use 10 gallons of water to rinse out the soil good enough to get rid of excessive nutrients. Soluble nitrogen (especially nitrate) is the form that’s the most quickly available to the roots, while insoluble N (like urea) first needs to be broken down by microbes in the soil before the roots can absorb it.

Note: Blood Meal, Dried Blood, Guanos, Kelp Meal, Cotton Seed Meal, Peat Moss, Sulfur and fish meal are all acidic and can bring your ph down, so if you add these please monitor your ph when using those.

Note: Bone Meal, Rock Phosphate, Wood Ashes pretty much all ashes, Shellfish Compost and Crab Meal are all alkaline and can make your ph go up, so if you add any of these please monitor your ph.

Hope this helps



It looks perfect for flowering. Keep the leaves from turning blue from adding Nitrogen. I am finding plant color to be a very good indicator of heath, as @garrigan62 mentioned above. In the beginning of flower I have read here, yellowing at the bottom leaves and a bright green leaf means you are headed for some good tasting herb. I am in the 6th week of flower on these Water Water everywhere how are we doing? These plants have received no nutrients until the plants color and “look” indicated it needed nutrients. There was no need for any until just before flowering. The medium was sufficient. It has been getting 2-7-7 since and just went to 4-14-14, because yellowing was progressing up the center slowly. I believe it is better to be easy on the nitrogen (safe than sorry). Per @MacGyverStoner 's suggestion I am gently going to hold the nitrogen at 4-14-14 to give it just a bit more for a short while. Any “blueing” of the leafs at this point in flowering would probably be very bad for taste. Watch out for granular slow release. To much nitrogen in the flowering stages is a bad thing! Make sure you know what you are putting on it in flower. Low or no N, Higher P and K. Excellent search engine here. Look for why they turn yellow at flower.

And… Welcome Aboard!

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Check it out.


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Garrigan, bmorgil and MacG, thank you guys so much for your responses!

After reading, reading and reading some more I think I misdiagnosed the issue. As mentioned in Garrigan’s post, Magnesium and Nitrogen deficiency have similar symptoms. After initially thinking it was an N deficiency I think lack of Magnesium is to blame. Below is a pic of one of the fan leaves starting to turn. Does it look like a M deficiency to you guys?

Maybe. Also maybe zinc, iron, sulfur and/or calcium. It could be more than one thing. And they all could be related to a pH too far out of range.

Check out the rest of or guides on nutrient problems. It also has other sections to consider, including pH.


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@Merk, If your soil mix was good, and since it is an outdoor grow, I would wonder about that. You can test for nutrients, though it is out of my area. I think if the moisture is right let the N shot you just gave it have a chance. Just remember, it is supposed to yellow the big fan leaves as it flowers. To much nutrient is very hard to come back from. To little is much easier to control. Leaf color is key. My thoughts!


Yes it dose. Here are a few pic’s of Magnesium

There are several ways to resolve magnesium deficiency, but one of the better options is a product called Marijuana Booster. This is one is very popular amongst marijuana growers because it is great for enhancing the quality of yields and provides a good balance of nutrients.

More options are:

Dolomite lime
Magnesium sulfate
Garden lime
Worm castings
Epsom salts
Since both Epsom salt and Magnesium sulfate (wiki) are water soluble, they work the best. For hydroponics systems, Epsom salts are by far the simplest solution. For every gallon of water in your tank add a teaspoon of Epsom salts. Give it a quarter of the initial dosage for every consecutive treatment. If you like, you can even add Calcium-Magnesium (available at this link for only $20)

Magnesium and pH levels
Magnesium ph levels weed

If the pH of your plants roots get too low, the marijuana plant could display signs of magnesium deficiency, even more so in hydro (check these hydro ph levels). This occurs as a result of the pH of the roots not being at the right ratio, which causes the plant to not properly receive magnesium from the roots.

Usually with this deficiency, the magnesium is there, but the roots are not able to receive the magnesium efficiently because of the wrong pH. This is why it is necessary to keep the right pH so as to prevent magnesium deficiency.

Download my free marijuana grow guide at this link for more growing tips

Providing additional magnesium to a system that has a pH lock-out will most likely not help since the plant can’t take in any magnesium until the pH is made right. If your plant has plenty of magnesium, giving it more could result in the development of other deficiencies by shutting out other nutrients the plant needs.

If you’re growing marijuana in soil, magnesium is better received by the roots in the 6.0 – 7.0 pH rate. If your’re growing marijuana in hydro, magnesium is better received by the roots in the 6.0 – 6.5 pH rate.

Try Flushing

If suspicion sets in and you begin thinking you plant has a magnesium deficiency, flush the system with pure, pH’d water that has a normal dose of marijuana-friendly nutrients in it which should include magnesium. This serves to get rid of all nutrient salts that are may have damaged the plants ability to absorb magnesium and help replenish the pH to the right ratio.

Read the article How to rinse a hydro system for more information about flusing

Back to top
List of marijuana plant symptoms
Leaf Color:
– Edges Look Brown or Burnt
– Pale Color Leaves
– Lower and Older Leaves Turn Yellow
– Yellowing Between Veins
– Veins of Leaves Stay Green
– Brown or Dark Spots
– Speckled / Patchy Pattern

Leaf Symptoms:
– Lower Leaves and Older Leaves Damaged
– Leaf Tips Look Burnt
– Leaf Tips Die
– Yellowing Between Veins
– Veins of Leaves Stay Green
– Spots
– Speckled / Patchy Pattern
– Old Leaves Dropping Off
– Twisted Growth
– Leaves Curl Under
– Leaves Curl Upwards
– Withering / Drooping

Plant Symptoms:
– Old Leaves Dropping Off
– Twisted Growth
– Leaves Curl Under
– Leaves Curl Upwards
– Plant Withering / Sagging

Prevent magnesium deficiency weed

If you properly resolve the issue, the yellowing and discoloration of the leaves should cease almost instantly. Some damaged leaves could bounce back to a certain extent, but what matters the most is that you ensure the issue is not still spreading to the other leaves on the plant.

We suggest not getting rid of the discolored leaves until you are certain the issue is totally resolved and is not spreading to the newer leaves. It is better if any continued discoloration occurs on the leaves that were already damaged.

Download my free marijuana grow guide at this link for more growing tips

All in all, pay close attention to the growth of your plant and if you suspect any issues use the list of symptoms to determine if there is a deficiency. Once you have followed the proper steps to restore balance, remember that it may take a few days before the deficiency is completely cleared up.

And remember that plants with strong genetics have less change of getting sick. Make sure you buy marijuana seeds from a trusted seedbank.

Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible
Robert Bergman
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@garrigan62, It seems like the leaves are all yellow with no spotting or green left in the “veins”. Couldn’t it be N or, normal for flowering?

Thanks again guys for all the info, much appreciated!

I’ve been running good soil from the start (Roots Organic 707) and picked up some Cal Mag + (Calcium/Magnesium/Iron) to address this issue. It’s only been a couple of days but I think I’m on the right track.

Obviously different plants, different genetics need different things. Only 2 of my ladies (same strain) are having this issue. The rest of them (2 other strains) couldn’t be doing any better. They are all on the same nute schedule in the same soil and obviously the same environment.

The PH of my water straight out of the tap around here sits at about 7. No one I know around here, or otherwise, PH’s their water in outdoor grows. I’ve done a few outdoor grows here and never ran into this issue.

I’m going to give it 3-4 more days. If I don’t see any improvement, I think it’s time to flush (w/ ph’d water) and go from there.

Pic’s below of my to afflicted ladies, they just started week 3 of flower today. As you can tell they look pretty good.


Nice! I think they look pretty good. You sure you want to mess with that crop?

I was thinking the same thing @bmorgil but the water he is using should be P H at 6.3 6.5
But ya they do look nice !

By the way you ask an early question about yellowing n flower ( seems like the leaves are all yellow with no spotting or green left in the “veins”. Couldn’t it be N or, normal for flowering? )
Ya sure, but how much depended on how far in flower they are…to early something’s wrong late in floiwer alls good… Don’t figure dose it…lol



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Gentleman, I’m at a bit of a loss on this one. A quick recap: Initially I thought it was an N deficiency. I picked up some N boost and supplemented their nutes with it. (Started w/ about 1/4 dosage, worked my way up to full dosage over a weeks time and didn’t see improvement)

After posting here and reading your responses (thanks again btw) I was convinced I had confused a N deficiency with a Magnesium one. “Nitrogen deficiency starts around the tips and works its way to the back of the leaves, where a magnesium deficiency will cover the entire outer part of the leave and make the entire leaves yellow.”

So I picked up some Cal-Mag +. So here I am 5 days later and I’m still seeing yellow leaves and some of them are creeping up mid to high plant. However all the flowering sites look perfect, and pretty impressive for only 3 weeks into flower.

I’m no expert but leaves yellowing this early in flower is abnormal, no? Could giving them bloom nutes, and maybe more specifically no grow nutes, too early in flower cause this?

How should I proceed guys? Is it flush time?

@Merk, I am certainly no expert either but, yours look awesome to me Just like mine did as far as the coloring and lower yellow leaves. I am now in the 7th week of flower and most of my Large fan leaves have all fallen off now. Just like yours it started from the bottom up. Mine started yellowing on the bottom the day they started to flower. I think I have read here that if you don’t have this natural yellowing during flower, the smoke could be harsh from to much N. Maybe we can get @garrigan62 to give us an opinion.


I answered to your question is in a post just above these four posts.
Ya gota read my friend! :wink:


Same happened with my outdoors last year and its all to do with ph… Im sure you could continue and finish your grow without ph’ing the water, leaves would keep on yellowing, but the plants could finish nicely still possibly… But if you want your crop to be the very best it can, you gotta get the PH right. Can be the difference between a good, and a great crop.

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@garrigan62, sorry Will… gotta pay attention to what I read! :blush:

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@BondPacker, what is a reliable inexpensive way to check the PH on an outdoor grow?

I’ve been PH’ing the water to 6.3 - 6.5 every time now. It is rather odd as none of my other ladies are having this issue. Maybe this variant (Jillybean) is more susceptible/finicky…

Or maybe I stumbled upon the first auto defoliating plant. LOL (sarcasm)

It does seem odd for leaves yellowing this early (halfway through week 3). However none of the flower sites have any yellow, at all.

Thanks again to everyone that has helped me out!