Is it common for marijuana plants?
Magnesium (Mg) deficiency is not common when growing marijuana outdoors. It is common in hydro and all mediums.
This deficieny will start in the lower leaves of the cannabis plant. The leaves turn yellow (exhibiting chlorosis) except for the veins, these remain green. Eventually the leaves curl up and die. The affected leaves experience dryness and become crispy at the edges. The deficiency moves from the lower leaves to the middle and finally the upper half of your cannabis plant. The growing shoots turn from a pale green to a white color, eventually. In the upper leafs the deficiency is quite apparent. The petioles and stems turn purple at the same time.
The mobility of magnesium is normal. It is mobile.
Role in nutrition of the marijuana plant
Healthy veins are supported by magnesium. Magnesium also maintains structure and leaf production. For production of chlorophyll and enzyme breakdowns, magnesium is required.
Solving the problem
To fix the deficiency use water-soluble nutrients containing magnesium. For example use magnesium sulfate (MgSO4, Epsom salts). For fast absorption use Ca-Mg. For a moderate absorption use dolomitic lime, garden lime and worm castings.
In planting mixes and hydro the deficiencies are easily fixed. Use 1 teaspoon of Epsom salts per gallon of water in reservoirs. Use 1 teaspoon per quart of water in planting mixes. After you have done the first treatment, treat with one quarter dose. Use one quarter dose with every change of water reservoir or watering. You can also use calcium-magnesium.
Use 1 teaspoon per gallon of Epsom salts for the fastest action. Use it filially. Also calcium-magnesium can be used filially.
Dolimitic limestone cannot only be uses to raise the pH of the soils and planting mixes but also for magnesium deficiency. It contains a large amount of magnesium. So it can be used for two causes.
Discussion in general
This deficiency is the most easy to diagnose and cure when growing marijuana. If you use tap water and distilled, reverse osmosis water that has a low ppm, it occurs frequently.