Cal Mag Deficiency - How to Identify and Treat Symptoms

A Cal Mag deficiency will almost certainly result in a diminished harvest. As a result, it is very important to address this issue as soon as you notice symptoms. Luckily, a cal mag deficiency is easy to spot and fix.

Calcium Deficiency

Calcium is fundamental for cannabis growth. Early signs of calcium deficient plants include: leaves that contort and curl and yellow/brown spots on leaves. Calcium deficient plants generally grow slow and have a diminished harvest. When compared with soil grows, hydroponic gardens tend to require more cal-mag fertilization.

Calcium Overdose

Too much calcium can also have a profound impact on your harvest. However, identifying a calcium overdose is somewhat difficult because of the subtle symptoms. Calcium overdose symptoms include stunted growth and minor leaf wilt. Lastly, excess calcium blocks the intake of other fertilizers and elements such as iron, potassium, manganese and magnesium.

Magnesium Deficiency

Cannabis requires a great deal of Magnesium for a bountiful harvest. Cannabis plants suffering from a deficient amount of Magnesium usually begin to show symptoms between weeks 4 and 7. Spots usually appear and leaves turn yellow/brown. Finally, the bottom leaves usually dry, curl and fall off.

Magnesium overdoses on the other hand are rare and tough to identify. Leaves tend to darken and growth is slowed.

Cal Mag Deficiency Products

Just like any issue you encounter in your garden, it is super important to address these issues as soon as possible. Luckily, Cal Mag fertilizers are cheap, work fast and easy to apply. Here are couple quality brands:

Botanicare Cal-MAG Plus Plant Supplement 2-0-0 Formula, 1 Quart – This Cal Mag fertilizer is a great buy. You can get 1 quart for less than $20. Botanicare 2-0-0 has calcium, magnesium, iron and trace minerals.
General Hydroponics CALiMAGic Quart – General Hydroponics is an OG when it comes to fertilizers. They are always reasonably priced despite being high quality. This Cal Mag fertilizer is formulated to assist fast growing plants by preventing secondary nutrient deficiencies.
Fox Farm Gringo Rasta Cal-Mag Quart – You’ll have to fork out a little more cash for this Fox Farm Gringo Rasta, but I think it is worth it. This Cal Mag fertilizer helps strengthen cell walls and aid in fruit development. It is also OMRI Listed^® and registered CDFA Organic Input Material.

How Much Cal Mag per Gallon

For best results, refer to the directions on your particular Cal Mag fertilizer. However, before applying flush your soil with clean water to remove excess salts.

For general instructions I would shake well before use. Mix between 1/2 tsp (2.5 mL) and 1 tsp (5 mL) per gallon (4 L) of water. Begin use when symptoms are present or just before bud development.

When to Stop Using Cal-Mag

Continue use as needed, though not more than once per week. Also, maintain a stable pH range between 5.5 – 6.8. Stop using Cal Mag when symptoms seize and plant resumes normal growth.

Final Thoughts

I hope this short blog helped! If you have any questions, please post them in the comment section. If you are interested in learning more about growing cannabis, please check out my blog. Here are a few of my most recent: