As a novice cannabis grower, you might be very puzzled when you discover that your marijuana plants are not thriving. Not all cannabis plant problems are brought about by diseases and insects. Sometimes it is something as simple as a nutrient deficiency or overload. When a plant is experiencing a nutrient deficiency, you will often notice discoloration as well as distortion of its leaves and stems. 

Before you kill your plant with too much love, read nutrients, ensure that you have properly diagnosed the problem and eliminated other factors.

How best can you deal with a deficiency of magnesium in your cannabis plants?

Magnesium is integral in encouraging the development of veins that are strong and healthy, and also providing stimulus for the creation of marijuana leaves. It also helps in the production of chlorophyll as well as breaking down enzymes. 

Magnesium deficiencies in weed are most prevalent indoors and in hydroponic systems growing. Not dealing with magnesium deficiency in weed on time could have detrimental effects on your cannabis plants including stunted growth. We have prepared some tips to help you avoid and overcome magnesium deficiency in weed. 

What is Magnesium Deficiency in Cannabis?

As we have mentioned, magnesium is an essential nutrient that is an important part of the chlorophyll molecule. Chlorophyll gives plants their green color and is used to convert sunlight to energy through the process called photosynthesis. 

Magnesium deficiency occurs when the plant is not getting enough chlorophyll and results in leaching it from other parts of the plant.

Magnesium is a mobile nutrient in plants. Therefore, when deficiency occurs, the chlorophyll in older leaves gets broken down to be transported to the plants’ new growth. It could also be described as the plant pulling magnesium out of the older leaves to the newer leaves. This is the reason why chlorosis symptoms manifest first in the older leaves.

However, if the deficiency does not get corrected in time, the chlorosis slowly spreads upwards eventually taking over the whole plant, including the new growth. This later leads to leaf necrosis, which leads to the dropping off of older leaves.  

As we have earlier mentioned, magnesium activates various enzymes. A deficiency therefore means that there will be a decrease in enzyme activity which will have disastrous effects on the plants. 

Magnesium also stabilizes the ribosome structures. Breakdown of these structures will cause the cannabis plant to experience premature aging. 

Other important roles magnesium plays that can be affected by deficiency are: 

• Nutrient uptake control.
• Plant fat and oil formation.
• Increases iron utilization.
• Sugar synthesis.
• Starch translocation.

Luckily, plant magnesium deficiency is easy to fix once you have identified it. Read on to learn how.

What Puts Your Plants at Risk of Magnesium Deficiency?

As we mentioned at the start of this article, marijuana magnesium deficiency is more common on weed grown hydroponically and that grown indoors. This is because soil is a much better medium for adding, maintaining, and dispensing magnesium and other nutrients. Let us see how some mediums disadvantage plants as far as magnesium is concerned. 

Coco coir: This is a great growing medium that is most often used in indoor marijuana growing. It however sometimes leads to problems as far as micronutrient uptake is concerned.  The adsorption of magnesium, as well as iron and calcium is usually a bit difficult for plants grown in coco coir. 

Incorrect PH in Hydroponic systems: When growing your cannabis hydroponically, if you let your nutrient solution slip to 5.0 or below, your cannabis plants will most likely experience magnesium deficiency.  Water with a PH that is too low usually leads to micronutrient lockout.

Overwatering: When cannabis plants are grown indoors, the chances of over watering are even higher as the rate of evaporation is slower than that of cannabis plants grown outdoors. Overwatering leads to soggy roots, which inhibits the absorption of nutrients including magnesium. 

Use of lightly fertilized soils:  These soils which are usually fertilized with liquid nutrients often lack the trace elements of vital nutrients. This often leads to the cannabis plants unexpectedly experiencing a magnesium deficiency especially during mid-late bloom. As the weed plant matures, the roots essentially take up all the micronutrients that were available in the medium and without adequate supplementation, the marijuana plant experiences magnesium deficiency.

What are the Symptoms of Magnesium Deficiency in Weed?

Like with other micronutrient deficiencies, the symptoms of magnesium deficiency will start from the roots and work their way upwards towards the rest of the plants and eventually into the new shoots. Though the symptoms of different nutrient deficiencies might often appear similar, those of magnesium deficiency are distinct in both appearance and method. 

We will discuss some of these symptoms:

 Yellow Leaves

One of the very first magnesium deficiency symptoms in cannabis is chlorosis. Chlorosis is when the leaf structure that is found between the veins yellows, giving the leaf a “marbled appearance”, as the veins still maintain their green color or turn red. Another indication that your cannabis plant is undergoing chlorosis is if the margins of its leaves begin to turn a red-brown-purple color.

The edges of the cannabis leaves may also become bright green or yellow and may feel slightly crispy to the touch. While nutrient burn may also inspire crispiness around the edges, it is different in that nutrient burn does not cause a change of color in the margins within the leaves.  

Red Stems

Though this symptom does not appear in every case of magnesium deficiency, red stems are usually a good indicator of cannabis magnesium deficiency.

How to Tell if you Have Cal Mag or Mag Deficiency?

In cannabis plants, Calcium and magnesium deficiencies usually appear together. This is why more often than not, you will find a cannabis grower buying a Calcium-Magnesium (or just Cal-Mag) supplement in case their plants start experiencing any one of these deficiencies.

To better understand how cal-mag deficiency in weed occurs, we must first understand nutrient mobility as a concept. Once plants absorb nutrients for consumption, some are immobile, while others are mobile. 

Once immobile nutrients are deposited in a certain part of a plant, it cannot be moved for use elsewhere in the plant, however much the other parts of the plant require it.

Mobile nutrients on the other hand can easily be transported between different parts of the plant even after being deposited. 

While magnesium is a mobile nutrient, Calcium is immobile. Cannabis plants that experience calcium deficiency exhibit in the opposite way magnesium deficiency shows. Calcium deficiency first affects the tips of young leaves, young buds, and young fruit unlike magnesium deficiency which affects the older parts of the plant, especially leaves first. 

Calcium deficiency also leads to localized rot. 

A common symptom of both calcium and magnesium deficiency are stunted growth.  

While calcium deficiency leads to root rot, magnesium deficiency in marijuana leads to the yellowing of leaves and the eventual aging and death of cannabis plants.

How to Differentiate Between Magnesium Deficiency and other Nutrient Deficiencies

The main differentiator between mag deficiency and other nutrient deficiencies is the breaking down of chlorophyll. Because magnesium is the main ‘building block’ of chlorophyll which gives the cannabis plant its vibrant green color, the absence of it will lead to a pale or faded green, which later turns to yellow. 

This process is called chlorosis. Although other deficiencies could also lead to chlorosis, in magnesium deficiency it will first show in between the leaves’ veins and around the edges, rather than from the stems outwards, from the tips inwards, or just all over.

Mg deficiency in cannabis also manifests from the lower leaves, upwards. The first leaves to discolor will be the ones that are oldest and closest to the bottom as the plant tries to extract the magnesium and transport it to the younger leaves and buds in a bid to keep itself alive (in the same way the human body will pull blood from the extremities to keep the vital organs warm during extreme cold weather). If this is unchecked though, it will spread to the whole cannabis plant. 

In mag deficiency in cannabis, the leaves may also start feeling crunchy and dry, which might not happen with other deficiencies. 

How to Fix Magnesium Deficiency in Cannabis

Though several correctional options exist that can be used to correct magnesium deficiencies in weed plants, we will discuss two that involve flushing:

Flush your Plant and Upgrade your Nutrients 

You might be wondering how to “flush” your cannabis plants.

It’s very simple, really.

Solving the magnesium deficiency in your cannabis plants should begin with “a flush” of 6.0 pH water. This should be optimal for all substrates. After you have flushed the substrate, you can now adjust the PH to the required level, which is 6.0-6.5 for soil and 5.5-6.0 for hydro.

Once your PH is correctly adjusted, you can now add the usual mix of required supplements, ensuring to incorporate a high quality magnesium supplement that is cannabis-specific.

Flush your Plant and add Supplements 

Rinse out the substrate with the 6.0 PH water as described above. Now, instead of adding a supplement, carry out a nutrient upgrade.

For this you can use specific nutrient lines that are customized to soil, hydro grows, or coco. This will make life so much easier for you. Some premier brands base nutrients are formulated to contain the complete micro and macronutrients needed for your cannabis plants. 

How to Fix Magnesium Deficiency in Weed Plants

Cannabis tends to have a higher demand for magnesium, which is why symptoms of magnesium deficiency will appear in them faster than in other plants. To avoid this deficiency, growers need to increase the amount of magnesium available in their irrigation water and growing mediums to ensure that this deficiency does not set in, causing irreparable damage to their cannabis plants. 

Magnesium Deficiency in Cannabis Q&A

What is magnesium deficiency in cannabis?

Magnesium deficiency defines the lack of sufficient magnesium that is characterized by a bottom to top leeching of the mineral. This leads to unhealthy looking growth in the lower part of the plant. At the start, the bottom leaves will yellow and become pale, while the tips will dry out and become a crunchy brown. 

Because magnesium is a mobile nutrient, magnesium deficiency is also mobile. If left unchecked, it will spread to the rest of the plant with dire consequences. As the deficiency gets to the shoots, they will become purple as the leaf chlorosis accelerates. 

How fast a grower will react will become a determining factor in whether the plants can be saved. 

A big mistake often made by novices is mistaking magnesium deficiencies for nitrogen starvation. This makes them increase nutrient dosing, which could lead to nutrient lockout. 

No matter the stage your cannabis plants are at, yellowing leaves from the bottom and brown spots, also starting from the bottom are a red flag signaling magnesium deficiency. 

How do you fix magnesium deficiency?

Fixing magnesium deficiencies is fortunately quite easy. Apart from flushing the soil and adjusting the minerals, another simple solution is using Epsom salts. But before you embark on a treatment method, always make sure that you have diagnosed the problem correctly. If you apply excess nutrients that the plant does not need, you might trigger a whole other plethora of problems. 

How to use Epsom salts: This quick-fix emergency measure is carried out by mixing water with magnesium sulfate to create a foliar spray that is often effective. The commercial name for Magnesium sulfate is Epsom salts, which is easy to purchase online as well as from large pharmacies.

The ratio of making a foliar spray is mixing one tbsp of Epsom salts to four liters of water. This mixture can then be sprayed onto the plants once every three days, A clean water spray can be applied every ten days to make sure no residue builds up on the cannabis leaves.

In summary, magnesium deficiencies can be fixed by:

• Flushing the soil/other medium
• Testing the pH level
• Supplementing the medium
• Dolomite lime
• Magnesium sulfate
• Garden lime
• Epsom salts
• Worm castings.