Problem: A cannabis nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away, and eventually die.
The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of âfoldâ in, before turning crispy and falling off on their own.
If the yellowing leaves are at the top of your plant or the yellow leaves are mostly new growth, then you probably donât have a nitrogen deficiency. Nitrogen deficiencies always affect the oldest, lowest leaves first.
Nitrogen is a mobile nutrient, which means it can move through the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. all new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant âwantsâ to give those leaves property for getting light.
If new leaves arenât getting enough nitrogen, the plant will start to âstealâ nitrogen from the older, lower leaves, so that it can give it to newer leaves. This is what causes the yellowing and wilting of a nitrogen deficiency.
Itâs relatively normal for your cannabis plantâs leaves to start turning yellow towards the end of your flowering cycle as the plants becomes nitrogen deficient while creating buds.
However, if your cannabis plant is losing leaves fast due to yellowing (if yellowing and dying leaves is âclimbingâ up the plant from the bottom), especially in the vegetative stage before the plant is making buds, you have a problem that you will need to fix as soon as possible.
You donât want a nitrogen deficiency in the vegetative stage!
If you notice your lower cannabis leaves turning yellow in the vegetative stage or in the beginning part of the flowering stage, your plan may be experiencing a nitrogen deficiency which will need to be treated.
It is not good if your cannabis plant is showing signs of an advanced nitrogen deficiency while still in the vegetative stage. Itâs normal to lose a few yellow leaves off the bottom of your plant here and there, especially with very big plants. But if you are losing a significant amount of yellow leaves, and the yellow seems to be moving up the plant quickly, then you have a problem.
As a grower, youâre interested in how much nitrogen to give your plants at what time. The ratio of nitrogen to other nutrients has a huge effect on growth and bud formation.
Vegetative Stage â higher levels of nitrogen (pretty much any plant food will do)
Most complete plant foods that you get at a gardening store contain high levels of nitrogen (N). These nutrient systems tend to work well in the vegetative stage.
Some examples of cannabis-friendly one-part vegetative nutrient systemsâŚ
Dyna-Gro âFoliage Proâ
General Hydroponics âFloraNova Growâ
Pretty much any complete plant food
Flowering Stage â lower levels of nitrogen (use âBloomâ or Cactus nutrients)
Itâs extra important to find nutrient system with lower levels of nitrogen for the last part of your plantâs life. Many âBloomâ or âFloweringâ style base nutrients are just the ticket.
Some examples of good one-part Flowering nutrient systemsâŚ
General Hydroponics âFloraNova Bloomâ
If you canât order online and canât find a good one-part bas Bloom formula locally, you do have other choices. Though this is not an ideal choice, most Cactus plant foods will contain good nutrient ratios for growing cannabis during the budding stage. So in a pinch, you can use the cactus nutrient that can be found at most gardening stores.
The first cannabis plants pictured below is showing signs of nitrogen deficiency late in flowering; nitrogen deficiency in late flowering is completely normal and even desired. The last picture is an infographic about nitrogen and your marijuana plant.
Itâs normal for plants to show signs of a nitrogen deficiency as the plant gets close to harvest. This is actually a good thing! Too much nitrogen can actually prevent proper budding, and can reduce the overall taste and smell of your plant. This is why all âbloomâ and flowering nutrient formulas are relatively low in nitrogen.
So donât swear it if you see your cannabis show some signs of nitrogen deficiency late in the flowering stage! Relatively low levels of nitrogen in the late flowering stage helps promote proper cannabis bud development and will increase your yields!
Donât worry about yellow leaves close to harvest!
Solution: You can find many pre-mixed nutrients from the store which contain nitrogen or you could use nitrate of soda or organic fertilizer which are both good sources of nitrogen. In fact almost all plant nutrients of any kind will include nitrogen. If you havenât been providing any nutrients to your plants, try supplementing your regular nutrients with a bit more nitrogen and see if the plant starts recovering.
If youâve already been using nutrients, then you probably donât have a nitrogen deficiency. If youâre seeing the signs of spreading nitrogen deficiency even a week or two giving nitrogen to your plants through nutrients, then you need to figure out what else is causing the yellowing so you can stop it.
More About Nitrogen and Your Marijuana Plants
Sometimes you can get the signs of a cannabis nitrogen deficiency if the pH at the plant root zone is too low, even if the nitrogen is there. This is because when the pH at the roots is not right, your plant roots canât properly absorb nutrients. If you arenât sure about your root pH, learn more about pH & growing cannabis plants.
Nitrogen is especially important during the vegetative stage of your cannabis plants. As your plants start flowering, they will need lower amount of nitrogen.
Nitrogen is one of the 3 nutrients that is included in almost every kind of plant food.
When looking at plant nutrients, youâll almost always see 3 numbers listed, like 3-12-6 or 5-10-5. These number represent the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K) contained in the bottle. Just about all plant life on Earth needs these 3 elements to grow.
The very first number, â3â in the case of the picture above, always displays the proportion of nitrogen in this nutrient bottle compared to the other 2 nutrients (Phosphorus and Potassium respectively).
The reason nitrogen is in all plant nutrient formulations is because itâs vital to plant processes.
Note: During the last few weeks before harvest, marijuana plants start pulling all the remaining nitrogen from her leaves as part of the bud-making process. This causes yelling leaves starting towards the bottom of the plant. This is part of the natural flowering process and you donât need to fight it. You may notice that marijuana leaves are yelling in almost all pictures of marijuana plants with big buds that are close to harvest. You tend to get smaller yields from nitrogen-toxic plants with dark green leaves at harvest.
Remember: Itâs normal for marijuana leaves to start turning yellow as harvest time approaches.
Occasionally a nitrogen toxicity is mistaken for a deficiency. Could your plant actually be nitrogen toxic? (pictured below)
Leaf Colour: Pale colour leaves, yellow leaves â lower, older leaves, yellowing between veins.
Leaf Symptoms: Lower leaves/Older growth affected, yellowing between veins, old leaves dropping off, wilting/drooping
Plant Symptoms: old leaves dropping off.
Problem: Dark green leaves, weak stems, and overall slow growth. Marijuana leaves that are nitrogen toxic often get âThe Clawâ or talon-like leaves that are bent at the ends. They also do an odd curving (or cupping) that is often mistaken for overwatering, but is unique to nitrogen toxicity. You can see a âclawingâ leaf pictured below.
Leaves that turn into claws often start turning yellow and dying if the nitrogen toxicity is not treated, much like a nitrogen deficiency, only the leaves will continue to get more and more clawed. Leaves eventually turn yellow or brown and fall off. You can tell if yellowing is cause by too much nitrogen because the rest of the plant will be dark green, and the yellowing leaves will turn into claws first.
The majority of times that growers encounter problems with nitrogen, itâs from giving too much of it to their plants.
Many new growers accidentally give their plants too much Nitrogen, especially in the flowering stage.
Your plant needs a lot of nitrogen in the vegetative stage, and itâs generally hard to give too much as long as youâre not going completely overboard with nutrients. Nitrogen is a big part of what makes leaves green, and is incredible important to the process of photosynthesis (making energy from light).
But cannabis plants need relatively low levels of Nitrogen in the second half of the flowering/budding stage. While your plants still need N (Nitrogen) during flowering, too much N at this stage will prevent your plants from forming buds properly, resulting in lower yields, less potency and possibly inferior buds.
This is why itâs important to avoid any type of âtime-releaseâ nutrients or soil (for example, standard Miracle-Gro soil) as they will keep giving your plants a lot of N even after its started flowering.
When it comes to nitrogen, this is what your plant needs:
Vegetative Stage â higher levels of Nitrogen (pretty much any plant food will do)
Most complete plant foods that you get at a gardening store contain high levels of nitrogen (N). These nutrient systems tend to work well in the vegetative stage.
Some examples of cannabis-friendly one-part Vegetative nutrient systemsâŚ
Dyna-Grow âFoliage Proâ
General Hydroponics âFloraNova Growâ
Pretty much any complete plant food
Flowering Stage â lower levels of Nitrogen (use âBloomâ or Cactus nutrients)
Itâs extra important to find a nutrient system with lower levels of nitrogen for the last part of your plantâs life. Many âBloomâ or âFloweringâ style base nutrients are just the ticket.
Some examples of good one-part Flowering nutrient systemsâŚ
General Hydroponics âFloraNova Bloomâ
If you canât order online and canât find a good one-part base Bloom formula locally, you do have other choices. Though not an idea choice, most Cactus plant foods will contain good nutrient ratios for growing cannabis during the budding stage. So in a pinch, you can use the cactus nutrients that can be found at most gardening stores.
Different strains react differently to nitrogen toxicity. Some plants get dark green leaves with no clawing. Some strains will get leaves that do the weird 90 degree bend at the tips, while other strains or individual plants start curling like claws and then turn yellow/brown and fall off like a deficiency. Yet these are all signs of too much nitrogen.
Signs of Nitrogen Toxicity
Dark green leaves and foliage
Leaf tips may turn down, without signs of overwatering.
You may notice yellowing on the affected leaves or other signs of nutrient deficiencies as time goes on
Nitrogen toxicity is often but not always accompanies by nutrient burn
The Claw often seems random, affecting leaves here and there
Heat and pH problems will make the clawing worse, as they stress out the plant and lower her defences, and cause her to drink more water (and uptake more N).
As time goes on, the claw leaves will eventually start turning yellow, getting spots, and drying.
Solution: Reduce the Nitrogen your plant is getting!
Reduce the amount of nitrogen that is being fed to the plants. If you are feeding extra nutrients, cut down that amount. If you are in the flowering/budding stage, make sure youâre using a formal thatâs specifically meant for flowering, or else it could have too much nitrogen.
If you are not feeding extra nutrients, you may have âhotâ soil that has been giving your plants extra nutrients. In that case, flush your plants with filtered, pHâed water to help clear out the extra nitrogen.
Effected leaves likely wonât recover, but you should see the problem halt with no new leaves being affected.
Wait! Iâm not sure if itâs Nitrogen Toxicity!
Ok, you ruled out overwatering, now what?
When I first got started growing, everyone kept telling me that this particular kind of leaf claw was caused by under or overwatering my plants, pH problems, or heat problems.
Yet in my case, I knew that I wasnât over or under watering (I was growing in hydro, where roots grow directly in water and air stones are constantly adding oxygen). I knew it wasnât pH (my reservoir water had the right pH) and I knew it wasnât heat since the grow area was slightly cooler than room temperature.
So then what was really causing my claw leaves?
Itâs understandable that other growers were mistaken. It is true that many stresses will make any other problem worse.
Plus overwatering can cause a similar kind of leaf clawing (learn more below). And if you do have nitrogen toxicity, then heat or pH problems will make the problem much worse.
Now, you may or may not know that marijuana (or any plant) needs an element known as âNitrogenâ to grow.
In fact, Nitrogen is one of the 3 nutrients that are included in almost every kind of plant food.
When looking at plant nutrients, youâll almost always see 3 numbers listed, like 3-12-6 or 5-10-5. These numbers represent the ratio of Nitrogen (N), Phosphorus (P), and Potassium (K) contained in the bottle. Just about all plant life on Earth needs these 3 elements to grow.
The very first number, â3â in the case of the picture below, always displays the proportion of the Nitrogen to this nutrient bottle compared to the other 2 nutrients (Phosphorus and Potassium respectively).
The reason nitrogen is in all plant nutrient formulations is because itâs vital to plant processes.
For marijuana plants, when they donât get enough nitrogen, the bottom leaves starting turning yellow and dying. Left unchecked, a nitrogen deficiency can cause the whole plant to eventually die.
However, this time weâre dealing with the opposite problem: nitrogen toxicity, or too much nitrogen.
Why You Should Treat and Prevent Nitrogen Toxicity
Marijuana plants that get too much Nitrogen in the vegetative stage donât grow as vigorously
Too much nitrogen is especially harmful in the flowering stage, because this will cause your plant to produce much smaller buds.
If you react quickly and reduce your nitrogen levels at the first sign of toxicity, your plant will quickly recover.
Note: Some strains with the word âClawâ in the name tend to do The Claw more easily than others
Problems with excess nitrogen are not common in the wild; itâs a lot more common to see nitrogen toxicity on indoor plants, especially when overzealous growers go overboard with nutrients.
Occasionally youâll come across a strain or particular plant that likes lower levels of nutrients, and when this happens, itâs important to realize the plan is showing signs of toxicity, even if all the other plants in your garden seem fine.
One of the most common signs of too-many-nutrients is ânutrient burnâ, or when the tups of your leaf appear brown or burned. Yet there are specific signals your plant will display when sheâs getting too much nitrogen.
Recap: How You Know You Have A Nitrogen Toxicity
dark green leaves and foliage
leaf tips turned down, without signs of overwatering
You may notice yellowing on the affected leaves or other signs of nutrient deficiencies as time goes on
nitrogen toxicity is often but not always accomplished by nutrient burn
The Claw often seems random, affecting leaves here and there
Heat and pH problems will make the clawing worse, as they stress out the plant and lower her defences, and cause her to drink more water (and uptake more N)
As time goes on, the claw leaves will eventually start turning yellow, getting spots, and dying
The distance between the leaves to the lights or irregular light patterns from reflectors often seem to affect the condition, which is why many growers believe that light is somehow causing the problem.
You may notice this clawing first appears on dark green leaves that arenât getting enough light (they arenât able to use up all their nitrogen and become nitrogen toxic).
The Claw in the Flowering Stage
If you use vegetative plant nutrients during the flowering stage, then theyâll deliver too much nitrogen. This is why you need to get special nutrients for the blooming/flowering stage. Youâll notice that flowering nutrients always contain a smaller percentage of nitrogen (the first number) compared to nutrients for the vegetative stage.
Many growers mistakenly keep raising nutrient levels or adding additional nitrogen when they see yellow leaves in the flowering stage, not realize that itâs natural for plant leaves to start yelling as harvest approaches. Adding too much nitrogen in the flowering stage can cause nitrogen toxicity even then you can see yellow lower leaves. Nitrogen toxicity in flowering results in smaller yields and airy cannabis buds, so make sure to watch out!
Note: During the last few weeks before harvest, marijuana plants start pulling al the remaining nitrogen from her leaves as part of the bud-making process. This causes yellowing leaves starting towards the bottom of the plant. This is part of the natural flowering process and you donât need to fight it. You may notice that marijuana leaves are yellowing in almost all pictures of marijuana plants with big buds that are close to harvest. You tend to get smaller yields at harvest from nitrogen-toxic plants with dark green leaves.
Itâs Normal For Marijuana Leaves to Start Turning Yellow as Harvest Time Approaches, Donât Keep Adding More Nitrogen!
I know a lot of marijuana plant problems can look similar, but now that youâre armed with the right information, youâll know exactly what to do if you see Nitrogen Toxicity affecting your marijuana plants.
Leaf Colour:
Edges appear brown or burnt, yellow leaves â lower, older leaves, dark or purple leaves, brown or dark spots
Leaf Symptoms:
Upper leaves/Newer Growth Affected, Lower Leaves/Older Growth Affected, all leaves seem affected, leaf edges appear burnt, leaf tips appear burnt, spots, leaves curl under, wilting/drooping
Plant Symptoms: Weak stems, leaves curl under, plant wilting/drooping
Other Symptoms: Buds not fattening.
Edit: Article edited for clarity
Source: This article was originally published on http://www.growweedeasy.com by Nebula Haze
Nitrogen Deficiency & Nitrogen Toxicity Nitrogen Deficiency Problem: A cannabis nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away, and eventually die.
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