By Miguel Ordoñez

Browse Deficiencies
Browse Deficiencies
Browse Deficiencies


Molybdenum deficiency will test the most eagle-eyed of cannabis growers. This one really is tough to diagnose correctly. Troubleshooting molybdenum deficiency will not only cost precious time, but most likely worsen the condition. Chlorosis striking the middle portion of cannabis plants foliage is commonly mistaken for nitrogen deficiency or calcium and magnesium deficiency.

In fairness, there is sound logic behind such assumptions. But don’t assume anything when it comes to unhealthy cannabis plants. Take a closer look. N deficiency tends to creep up a plant from the bottom up. Ca/Mg deficiency is rare in soil grows and more of a mid-late bloom problem in coco and hydro cultivation. Also, take note of the leaf discolouration, which will have brown crispy fringes and orange to pink shades in the centre. Eventually in a week or so, you will notice it is highly mobile as new growth begins to wither and curl.

Molybdenum deficiency cannabis plantation


Beginner hydroponics growers can potentially run into this problem quite easily. The lower pH range of 5.5-6.0 required for hydro cultivation can be tricky for novices using starter kits and pH pens for the first time. Dialling in pH to the optimal level for every feeding of nutrient solution takes practice to perfect. Unfortunately, hydroponics is unforgiving. Precision is a necessity. PH below 5.5 will cause a molybdenum lock-out.

Coco and soil growers are not exactly in the clear, although these cultivation styles are less prone to molybdenum deficiency. Peat and coco coir-based soil and soilless mix substrates act as a buffer for the root zone. 6.0-6.5pH is preferred. However, should the pH of nutrient solution be administered too low, too often a molybdenum deficiency can and likely will develop due to nutrient lockout.


Catch molybdenum deficiency early and it’s a simple 1-2 solution. Step one to remedy molybdenum deficiency and most cannabis ailments is a cleansing flush of the medium with pure 6.0pH water. The micronutrients the roots need are locked-out and the excess fertilisers need to be leached.

Step two is making sure the pH is perfect, per growing medium, for the follow-up feed of nutrient solution. Direct supplementation is not really an option as only trace amounts of molybdenum are required.

Molybdenum deficiency cannabis cultivation


For whatever reason, if you are delayed treating molybdenum deficiency, expect some permanent damage to your cannabis plants. In addition to the above 1-2 solution, a third, less pleasant step is required.

Step three is pruning away the necrotic growth. If plants are still in vegetative growth, it’s not the end of the world. Top plants and remove the dead and dying leaves. 2-3 weeks recovery will be required, depending on how far chlorosis spread. On the other hand, if you must prune during bloom, make sure to remove leaf stems when pruning flowers to avoid bud mould. Yield will be reduced. But a smaller stash is better than no stash.


As is the case with the majority of micronutrient deficiencies, the best way to avoid the headaches later is to invest in high-quality substrates and nutrients in the beginning. Using cannabis-specific growing mediums and fertilisers is recommended.

Furthermore, the grower must take responsibility and ensure the root zone is healthy at all times. Careful monitoring and adjustment of pH throughout the cannabis lifecycle are essential. Get a pH pen or pH-perfect nutrients. Either way, stay in control of feeding. If you can, your marijuana will avoid molybdenum deficiency. And most other nutrient deficiencies altogether.

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