Ensuring your marijuana plants receive the proper nutrients is crucial for strong, healthy growth.
Cannabis nutrient deficiencies often stem from soil, water, or fertilizer imbalances and can severely impact yields and quality if left unaddressed.
Different cannabis strains have different ideal nutrient ratios, but they all require vital nutrients to grow healthy and strong.
Unfortunately, many growers do not provide their plants with the right mix of nutrients, leading to deficiencies that can stunt growth, lower yields, and cause other problems.
This guide covers the most common nutrient deficiencies in cannabis, including signs to watch for, correction methods, and how to prevent further damage.
We’ll also discuss cannabis nutrient deficiencies and excesses, show you a cannabis nutrient deficiencies chart, and provide practical tips for testing and adjusting nutrient levels.
Table of Contents
Nitrogen deficiency
This is one of the most common cannabis nutrient deficiencies. Cannabis plants need nitrogen for growth and development, so lacking this nutrient can lead to stunted growth, yellowing leaves, and slow development.
Other symptoms of nitrogen deficiency include small leaves, fewer leaves, and a general lack of vigor.
However, don’t be confused with nitrogen toxicity, which can also cause leaves to turn yellow.
The difference is that with nitrogen toxicity, the new growth at the tips of the leaves will be yellow, while with nitrogen deficiency, the older leaves will turn yellow first and then progress up the plant.
Run some tests on your water and soil to see if nitrogen is low, and then fertilize accordingly. Be careful not to overdo it, as too much nitrogen can harm your plants.
Also, ensure you use a fertilizer high in nitrogen, as other nutrients will not do much to alleviate the deficiency.
Phosphorus Deficiency
Phosphorus is another essential nutrient for cannabis plants, and it is often one of the first nutrients to become depleted in soil.
Phosphorus is responsible for energy transfer and storage in plants, so a deficiency can lead to stunted growth, slow development, and reduced yields.
Plants with a phosphorus deficiency may also have purplish or reddish and small, dark-green leaves.
As with nitrogen, too much phosphorus can be as harmful as too little. If you suspect your plant has a phosphorus deficiency, test the soil and water to see if they are low in this nutrient.
You can also try preventing the deficiency by using a fertilizer high in phosphorus, but be sure not to overdo it. A natural way to add phosphorus to the soil is by using bone meal. To do this, mix bone meal into the soil around your plants.
Potassium Deficiency
Potassium is one of the most essential nutrients for cannabis plants, and a deficiency can cause several problems.
This nutrient helps with photosynthesis, water uptake, and the movement of nutrients throughout the plant.
A potassium deficiency can cause leaves to be yellow or brown and curl at the edges. It can also lead to stunted growth and smaller yields.
To correct a potassium deficiency, growers can use a potassium-based fertilizer or add potassium sulfate to their soil. However, before fixing a deficiency, it is always best to test the soil to ensure potassium is the problem.
But why is testing essential? First, over-fertilizing with potassium can cause problems, such as root burn, so it is essential to ensure that the problem is indeed a deficiency.
Calcium Deficiency
Calcium is essential for developing strong cell walls, and a deficiency can lead to stunted growth and problems with the roots.
Symptoms of a calcium deficiency include yellowing leaves (usually starting at the bottom of the plant), small or stunted leaves, and leaf tips that curl downwards.
Unfortunately, these symptoms can also be caused by other problems, so it is essential to look for other signs of a calcium deficiency, such as soft or spongy stems.
Providing your plants with the right calcium is crucial to prevent deficiencies. The best way to do this is to use a calcium-rich fertilizer, such as bone meal or limestone.
Like any other deficiency, it is essential to catch a calcium deficiency early, as it can be difficult to correct once the plant is already stunted.
Magnesium Deficiency
Magnesium plays an important role in photosynthesis, and a deficiency can lead to yellowing leaves (starting at the bottom of the plant).
Unlike with a calcium deficiency, the leaves will not curl downwards.
Magnesium deficiency is also often accompanied by a potassium deficiency, as these two nutrients work together in the plant.
A magnesium deficiency can be corrected using a magnesium-rich fertilizer, such as Epsom salt. It is important to ensure that your plants get enough water, as magnesium is water soluble and can be easily washed away.
Sulfur Deficiency
Sulfur may seem unlikely to be deficient, but it’s pretty common, especially in hydroponic systems.
In addition, sulfur is necessary to produce chlorophyll, so a deficiency will lead to yellowing leaves (between the veins) and slow growth.
Add a sulfur-based fertilizer to your nutrient solution to correct a sulfur deficiency. However, be careful not to overdo it, as too much sulfur can harm plant growth.
Iron Deficiency
Iron is another nutrient that is essential for chlorophyll production. An iron deficiency will lead to yellowing leaves (between the veins), stunted growth, and weak stems.
Yellowing leaves have other causes, so check for other cannabis nutrient deficiencies before assuming it’s iron.
You can use an iron-based fertilizer or chelate to correct an iron deficiency. Iron can also be applied as a foliar spray, but avoid getting any on the leaves as this can cause burning.
Cannabis Nutrient Deficiencies Chart
Below is a quick reference for identifying and fixing cannabis nutrient deficiencies.
This cannabis nutrient deficiencies chart provides a snapshot:
| Nutrient | Symptoms | Remedy |
| Nitrogen (N) | Older leaves yellow first, stunted growth | High-nitrogen fertilizer (e.g., fish emulsion) |
| Phosphorus (P) | Purple stems, slow growth, dark-green leaves | Add bone meal, guano, or P-rich fertilizer |
| Potassium (K) | Brown/yellow leaf edges, curling tips | Use potassium sulfate or a K-based supplement |
| Calcium (Ca) | Lower leaves curl, soft stems, yellow edges | Gypsum, dolomite lime, or calcium-based fertilizers |
| Magnesium (Mg) | Yellowing between veins on older leaves | Epsom salts, magnesium sulfate, balanced watering |
| Sulfur (S) | Overall leaf yellowing, weak growth | Sulfur-based amendments, check pH levels |
| Iron (Fe) | Yellowing in new leaves between veins | Iron chelates, iron sulfate, adjust pH |
Cannabis Nutrient Deficiencies and Excesses
Nutrient deficiencies aren’t the only cause of plant problems.
Excesses or toxicities can also lead to discolored leaves, weak stems, and reduced bud production.
For instance, excess nitrogen can cause leaf burn, while too much phosphorus may lock out other nutrients.
Always test your soil before applying additional fertilizers, and follow dosage instructions to prevent nutrient burn.
Testing & Adjusting Nutrient Levels
Soil & Water Testing
Use pH and EC meters or test kits to identify which nutrients are low or excessive.
Adjust pH
Cannabis grows best in a pH range of 6.0–6.8 for soil. If pH is off, nutrients can become locked out regardless of how much you feed.
Use Quality Fertilizers
Select balanced formulas with essential micros. Try targeted amendments (like bone meal, Epsom salts, or K boosters) for specific deficiencies.
Monitor & Evaluate
Check new growth weekly. If the deficiency persists, pH, feeding routine, and possible root issues should be reevaluated.
Frequently Asked Questions (FAQ)
Q1: How can I prevent cannabis nutrient deficiencies in my cannabis plants?
A: Maintain a balanced feeding schedule, test soil pH regularly, and use quality fertilizers designed for cannabis to ensure your plants get all essential nutrients.
Q2: Can I correct cannabis nutrient deficiencies with homemade solutions?
A: Yes. For example, Epsom salts fix magnesium issues, and bone meal boosts phosphorus. However, always confirm the deficiency and avoid over-fertilizing.
Q3: Should I flush my plants if I suspect a nutrient imbalance?
A: A flush with pH-balanced water can help remove excess salts or nutrients, resetting the root zone. Ensure the deficiency isn’t a toxicity before flushing.
Q4: What if multiple nutrient deficiencies appear at once?
A: Multiple deficiencies often indicate pH imbalances or overwatering. Check your pH first; consider cal-mag supplements or a complete nutrient formula if that’s on track.
Q5: Why are my leaves yellowing even though I’m fertilizing?
A: Over-fertilization can lead to lockout, where an excess of one nutrient prevents the uptake of others. Test both soil and run-off to diagnose accurately.
Conclusion
Addressing cannabis nutrient deficiencies early on is crucial for maximizing yields and ensuring vigorous plant growth.
Keep a close eye on leaf coloration, growth rates, and overall plant health.
Always test soil or hydro solutions, maintain proper pH, and use targeted fertilizers to correct nutrient imbalances—whether you’re dealing with cannabis nutrient deficiencies or cannabis nutrient deficiencies and excesses.
Using the cannabis nutrient deficiencies chart above, you can quickly identify and remedy issues to keep your plants on track. With the right approach and consistent monitoring, you can ensure your nutrient deficiencies in cannabis never get out of control.
Happy growing!
