Just like any other plants, marijuana requires adequate amounts of macro-nutrients as well as primary minerals for optimum growth and health. Magnesium (Mg) is one of the essential nutrients for cannabis plants. Since this element is one of the central components of chlorophyll, it plays the role of facilitating light absorption during photosynthesis. What’s more, magnesium helps to neutralize acidic substances and toxic compounds as well as utilization of plant energy. It is also a major supporting nutrient for a number of additional metabolic processes that are essential for the proper growth of marijuana plants.
When there is a deficit of adequate amounts of magnesium in marijuana crops, certain disorders may start to form. However, the onset of symptoms may not be noticeable right away because it takes 4-6 weeks for visible signs to start manifesting. Magnesium deficient marijuana leaves normally start to develop tiny necrotic spots that have a rust brown hue which is accompanied with a cloud like chlorosis that mostly affects middle aged foliage. As the deficiency progresses, the brown spots may spread to other leaves while the edges of leaves begin to turn bright green or pale yellow. At this point, the marijuana plants appear visibly sick due to the blatant chlorosis of foliage. When left unattended, magnesium deficiency can spread to young leaves and eventually causing the entire plant to die off.
There are many factors that may contribute to decreased root absorption of magnesium in marijuana plants. Contrary to popular belief, soil infertility is not always the reason behind most plant nutrient disorders. In fact, lack of magnesium in cannabis plants can occur when levels of this mineral are normal within the soil or when they are above the required range. An undeveloped root system can contribute to this problem or even when the root environment is too cold, acidic or extremely wet. In other cases, magnesium deficiencies occur when levels of ammonia, calcium and/or potassium reach toxic levels. Although quite rare, magnesium toxicity can also inhibit intake of this mineral along with other ions in the growth medium used for cultivating marijuana plants.
Once a proper diagnosis has been made based on the symptoms present, there are several methods available to help cannabis plants recover from a magnesium deficiency. The solution however will mostly depend on the underlying cause. Any attempts to correct the problem with the wrong measures can lead to further mineral intake problems, which ultimately slows down growth. It is therefore important to carefully establish the actual cause of the magnesium deficiency disorder in cannabis.
If you have been following a proper nutrient feeding schedule, then make sure to check whether there is a pH problem before adding more magnesium enriched fertilizers so as to avoid intoxicate your plants. Make sure to adjust your pH if it is too acidic or alkaline. On the other hand, if there is an apparent lack of adequate magnesium in the growth medium, you can make use of soil additives that contain Mg compounds, but be certain no to over fertilize your marijuana plants.