How to Spot a Nutrient Deficiency in Your Cannabis Plant

Cultivators can spot a nutrient deficiency by monitoring their plants for discoloration and structural issues, says Advanced Nutrients’ Michael “BigMike” Straumietis, allowing them to diagnose and correct common deficiencies such as nutrient lockout and phosphorus toxicity. Here, he offers insight on symptoms of these nutrient deficiencies, so cultivators can catch them early.

Cannabis Business Times: How can you spot a nutrient deficiency in plants?

BigMike: You can typically see there are problems due to color, stunted growth or other leaf problems. 

CBT: What should you be looking for in terms of color?

BM: Foliage will often turn shades of yellow. Regardless of color, plants don’t look healthy. They look sick.

CBT: What should you be looking for in terms of structure?

BM: You might notice your leaves becoming limp and lifeless looking. You may also see brown necrosis spots. Typically, these areas will be larger than pest damage and it’s easy to tell what your problem is.  

CBT: If you spot a deficiency, is there any point where it would be deemed too late to correct? 

BM: Obviously, you can wait too long, and your plants will die. One thing to watch out for, though, is misdiagnosing your plants.

Nutrient lockout can often be a problem. It occurs because during the growing process, your growing medium, over time, can accumulate excess nutrient salts and other substances. These can build up and raise the pH of the growing environment. This causes nutrient lockout because the pH is too low. The plants can’t feed off the nutrients you give them, causing more excess nutrients to build up, essentially causing a snowball effect. If you misdiagnose this as too few nutrients (because your plants look like they’re starving), then you can make the problem worse by feeding them more nutrients. Instead, you should flush your crops to clear out the excess nutrients.

CBT: How can you sample your products for deficiencies?

BM: While labs are able to perform tissue analysis and soil sampling, it’s often better to look at what plants are being fed and try to understand why those nutrients are not making it into the plant.

CBT: What’s the most common deficiency you see cultivators experience? 

BM: Besides nutrient lockout, I see phosphorus toxicity from growers who don’t use Advanced Nutrients fertilizers and supplements. In short, excess phosphorus affects the plant by locking out other elements, like calcium, copper, iron, magnesium and zinc. We specifically use lower amounts of phosphorus to avoid this problem. It was very controversial when we implemented our low-phosphorus policy years back, yet it has been proven correct, time and time again. 

CBT: What can we learn from traditional agriculture about nutrient deficiencies?

BM: The biggest thing we can learn from traditional agriculture is that cannabis plants are unique and require exacting amounts of specific nutrients almost totally unlike other traditional big agriculture crops like corn, soybeans and wheat.

Top image courtesy of Advanced Nutrients