Problem:A cannabis nitrogen deficiency makes older, lower leaves turn yellow and wilt. They will die off. The plant looks pale or lime-colored.
The yellow leaves may also show brown spots. They become soft and fold in. Then, they turn crispy and fall off.
Example of cannabis Nitrogen deficiency yellow bottom leaves. Almost all plant nutrients contain Nitrogen
Nitrogen-deficient plants look pale or lime-colored. The leaves on this marijuana plant are pale all over. They look almost lime green.
The light-colored leaves show the plant needs more Nitrogen. Plants with too much Nitrogen turn dark.
If the yellowing leaves are at the top of your plant or the yellow leaves are mostly new growth, then you probably don’t have a nitrogen deficiency. Nitrogen deficiencies usually affect the oldest, lowest leaves first, or the entire plant becomes light.
Nitrogen is a mobile nutrient. It can move throughout the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. New leaves get plenty of nitrogen to stay green and help with photosynthesis.
The leaves that get the most light are the newest, youngest leaves. So, the plant ‘wants’ to give those leaves priority for getting light.
If new leaves aren’t getting enough nitrogen, the plant will start to ‘steal’ nitrogen from the older, lower leaves. This is what causes the yellowing and wilting of a nitrogen deficiency.
It’s relatively normal for your cannabis plant’s leaves to start turning yellow towards the end of your flowering cycle. This is because the plant becomes nitrogen deficient while creating buds.
However, if your cannabis plant is losing lower leaves fast due to yellowing, especially in the vegetative stage before plant is making buds, you have a problem. You will need to fix this as soon as possible.
You don’t want a nitrogen deficiency in the vegetative stage!
IfIf your cannabis leaves turn yellow, it might mean your plant lacks nitrogen. This is a problem that needs fixing.
Seeing many yellow leaves on your cannabis plant is not good. Losing a few leaves is normal, especially with big plants. But losing lots of leaves fast is a sign of trouble.
As a grower, knowing how much nitrogen to give is key. The right mix of nutrients affects growth and bud formation.
Vegetative Stage needs more Nitrogen (use any plant food)
Most plant foods at gardening stores have lots of nitrogen. They work well when your plant is growing.
Some good one-part Vegetative nutrient systems for cannabis are:
- Dyna-Gro Foliage Pro
- General Hydroponics FloraNova Grow
- Any complete plant food
Flowering Stage needs less Nitrogen (use ‘Bloom’ or Cactus nutrients)
Finding the right nutrient mix for the end of your plant’s life is crucial. ‘Bloom’ or ‘Flowering’ nutrients are perfect for this.
Some good one-part Flowering nutrient systems are:
- Dyna-Gro Bloom
- General Hydroponics FloraNova Bloom
- If you can’t find the right nutrients online, you can use Cactus plant foods. They’re not the best, but they’ll do in a pinch. You can find them at most gardening stores.
The first cannabis plant shown 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.
It’s 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 ‘bloom’ and flowering nutrient formulas are relatively low in nitrogen.
Don’t worry about yellow leaves close to harvest!It’s normal to see a few Nitrogen-deficient leaves in the flowering stage. Nothing to worry about unless you see the yellowing leaves start climbing up the plant.
So don’t sweat it if you see yourcannabisshow some signs ofnitrogen deficiency late in theflowering stage! Relatively low levels of nitrogen in the late flowering stage help promote proper cannabis bud development and will increase your yields!
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 haven’t been providing any nutrient to your plants, try supplementing your regular nutrients with a bit more nitrogen and see if the plant starts recovering.
If you’ve alreadybeen using nutrients, then you probably don’t have a nitrogen deficiency. If you’re 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 can’t properly absorb nutrients. If you aren’t sure about your root pH, learn more about pH & growing cannabis plants here.
Nitrogen is especially important during the vegetative stage of your cannabis plants. As your plants start flowering, they will need lower amounts of nitrogen.
Nitrogen is one of the 3 nutrients that is included in almost every kind of plant food.
When looking at plant nutrients, you’ll almost always see 3 numbers listed, like 3-12-6 or 5-10-5. These numbers represent the percentage of Nitrogen (N), Phosphorous (P) and Potassium (K) contained in the bottle. Just about all plant life on Earth needs these 3 elements to grow.
The 3 numbers on the front of plant nutrient bottles list the amount of Nitrogen, Phosphorus, and Potassium.
The very first number,’3′ in the case of the picture to the right, always displays the proportion of nitrogen in this nutrient bottle compared to the other 2 nutrients (Phosphorus and Potassium respectively).
Nitrogen is in all plant nutrient formulations because it’s 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 yellowing leaves starting towards the bottom of the plant. This is part of the natural flowering process and you don’t 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 from nitrogen-toxic plants with dark green leaves at harvest.
Remember: It’s Normal For Marijuana Leaves To Start Turning Yellow As Harvest Time Approaches
