How to Spot and Correct a Cannabis CalMag Deficiency
If you want to grow the terpiest, tastiest, and most potent cannabis in town, you’ve come to the right place!
I’ve been working with the formulation and testing of cannabis nutrition and supplements for years and I think one of the supplements that every grower needs to have in their arsenal is a good CalMag product.
Cannabis CalMag deficiency is a very common problem for growers and it can wreak havoc on entire harvests. In this article, I want to show you how to spot a CalMag deficiency early and teach you how to correct it before it destroys your product.
If you already know you have a deficiency, view our CalMag for cannabis here.
(Ca Mg) CalMag: is short for Calcium & Magnesium fertilizer supplements. Calcium and Magnesium are essential nutrients for healthy growth and development in your plants.
Calcium helps fortify cell walls which in turn helps your plants transport nutrients. Calcium deficiency results in weak stems, curled leaves, and overall poor plant stability.
Magnesium plays an important role in photosynthesis (the process by which plants produce energy from sunlight) by stabilizing the chlorophyll molecule. Magnesium deficiency results in yellow and lackluster leaves.
Micronutrient: Absorbed in small to minute quantities. They are generally less well known than the macronutrients since most plant foods don’t contain them.
Symptoms of Cannabis Cal Mag Deficiency
It’s fairly easy to diagnose a Cal Mag deficiency but you need to know how to spot the early symptoms in order to treat it quickly, effectively, and definitively. If left untreated or treated too late, a CalMag deficiency will cause all kinds of issues to everything from the roots to the flowers.
- The first signs of a CalMag deficiency can be spotted in the new growth coming from the plant. If new leaves show signs of yellowing between the leaf veins with brown spots, curling (or parachuting) of the leaf tips, and stunted growth, you should suspect a CalMag deficiency.
- After that, you will start seeing interveinal chlorosis on new leaves as the low magnesium levels inhibit photosynthesis and chlorophyll molecules break down. The low levels of calcium will lead to weak stems and poor root development making the entire plant lose structure and posture.
- Finally, the nutrient deficiency during the flowering stage will lead to poor bud development, less flowering, and rotting.
Keep in mind that CalMag deficiency symptoms can be easily confused with other nutrient issues. Don’t worry – we’ll explore this further in the next section!
Possible Confusion with Other Symptoms
CalMag deficiency in weed plants can be easily confused with nitrogen deficiency, zinc deficiency, and silica deficiency. To accurately diagnose a cal-mag issue you need to consider these factors before jumping to any conclusions.
- Location of symptoms – Cal Mag deficiencies typically only affect new growth in the early stages. Nitrogen deficiency on the other hand impacts older growth that can be found lower down, towards the base of the plant.
- Pattern of chlorosis – Interveinal chlorosis is a telltale sign of CalMag deficiency, while nitrogen deficiency result in overall yellowing.
- Leaf curling with brown tips – Zinc deficiency can also result in curling leaves and interveinal chlorosis bit it differs in that it has more defined browning of the leaf tips.
- Early root issues – Silica deficiency also has leaf yellowing, curling tips, and spots on the leaves but it has more defined symptoms of poor root development and susceptibility to disease.
What Causes a Cal Mag Deficiency?
CalMag deficiencies are usually due to pH imbalances that inhibit the transportation of Calcium and Magnesium to the extremities of the cannabis plant. It normally only happens if your medium is too rich in phosphorous or when soil, that is treated with RO water, is too coarse and sandy.
There are 5 main factors that you should consider if you suspect a cannabis CalMag deficiency or if you consistently suffer from the same CalMag issues.
- Acidic or alkaline soil – Extreme pH levels can affect nutrient availability, leading to deficiencies. If your soil (or other medium) has a pH that is off, it is common to experience a CalMag deficiency. Cannabis plants absorb all nutrients most efficiently when the growing medium has a pH between 6.0 and 7.0 (slightly lower for hydroponics 5.5-6.5).
- Nutrient imbalance – Over-fertilization or the presence of other nutrients may hinder calcium and magnesium uptake. Use a cannabis-specific nutrient solution that is easy to use and that provides your plants with a balanced mix of macro and micronutrients.
- Treated water – Most tap water contains calcium and magnesium so it’s uncommon for beginners to suffer from CalMag deficiencies because they tend to start with tap water. If you are using RO (reverse osmosis) or distilled water you need to add all the nutrients back into the solution yourself and you may be underfeeding CalMag
- Soft water – Depending on where you live, you may have soft water in your tap. Soft water has lower levels of calcium and magnesium which can lead to deficiencies.
- Sandy coarse soil – Sandy soil drains very quickly and may not hold enough nutrients for your plants to efficiently take in sufficient nutrition.
How to Correct a Cannabis Cal-Mag Deficiency
Calcium and Magnesium are essential for cannabis plants so a deficiency needs to be corrected as soon as it has been diagnosed. If not, the plants will not grow into their complete form and will look wilted and weak (they end up looking quite sad and pathetic to be honest).
Perform the steps below and your plants should start to show signs of improvement on new growth. Depending on when you spot the deficiency, the plant should get back to normal in around 10-15 days.
- Adjust your pH – Ensure your growing medium has a pH between 6.0 and 7.0 for optimal nutrient uptake. CalMag deficiencies have a tendency to show up when the soil is too alkaline so you may need to add lime to your soil in order to raise the acidity slightly.
Use a pH meter and keep records of your soil pH to make sure you are not adjusting incorrectly.
If the pH is way off, you need to flush the system with clean RO water and reapply all the nutrients and supplements in balanced ratios. This is how you do a flush. - Use balanced cannabis nutrients – Use balanced nutrients that is not too heavy on phosphorus. This is especially important in the vegetative stage when your plants are too young to flower.
You may need to flush the system with clean RO water and reapply all the nutrients and supplements in balanced ratios if you have a nutrient balance that is out of control. - Supplement with Cal Mag – Add a high-quality CalMag supplement to your feeding regimen to provide the necessary calcium and magnesium that your plants need. Follow the instructions on the label.
- Check your water – If you consistently suffer from CalMag issues and you are using treated, distilled, or soft water you need to consider switching to a different source completely.
How Long Does It Take for a Plant to Recover from a CalMag Deficiency?
Recovery time depends on the severity of the deficiency and the overall health of the plant. In most cases, you can expect to see improvements within 10-15 days after addressing the issue. New growth will start to come out healthy but old growth will remain with symptoms until it falls or is cut off.
Severely hurt plants may never recover.
Why are Calcium and Magnesium Important to Cannabis Plants?
Calcium and magnesium play vital roles in the health and development of cannabis plants with Calcium mainly playing a key role in strengthening cell walls, supporting root development, and aiding in nutrient transport. Magnesium on the other hand is a key component of chlorophyll and helps during photosynthesis and energy production in the plant.
Together, CalMag is an essential blend for robust growth, healthy bud formation, and a bountiful harvest.
Can you overdose CalMag?
While it’s important to address CalMag deficiencies, it’s equally important to avoid CalMag toxicity. Overdoing it with Calcium and Magnesium can lead to nutrient lockout and may cause more harm than good. Signs that you are using too much Cal-Mag include.
- Leaf tip burn
- Reduced growth
- Nutrient imbalances
When to Stop Using Cal Mag
The use of cal mag during flower is essential for healthy bud development. However, as you approach the final week of flowering and the flush, you should stop using your cal mag suppliment.
Taper off your cal mag supplementation during the last 2-3 weeks of flowering to avoid potential nutrient imbalances and over-fertilization.
