The Importance of Calcium and Magnesium
Calcium and magnesium are two secondary macronutrients vital for healthy plant development, acting synergistically to support numerous physiological processes.
Calcium's Role
- Cell Wall Structure: Calcium is the building block of cell walls, providing structural rigidity and strength to the entire plant. A deficiency can lead to weak stems and stems that are susceptible to rot.
- Root Development: It promotes the growth of a robust root system, which is essential for efficient nutrient and water uptake.
- Nutrient Transport: It helps regulate the transport of other nutrients, like potassium and nitrogen, within the plant.
Magnesium's Role
- Photosynthesis: As the central atom in the chlorophyll molecule, magnesium is directly responsible for photosynthesis, the process by which plants convert light into energy.
- Enzyme Activation: It activates many plant enzymes, including those involved in energy transfer and the synthesis of proteins.
- Phosphorus Uptake: Magnesium improves the absorption and mobility of phosphorus, which is critical during the flowering stage.
When to Use CalMag
Supplementing with CalMag is not always necessary, but certain factors make it essential. The timing and approach depend on your growing medium, water source, and your plants' health.
Proactive Prevention
It is often more effective to use CalMag preventatively to avoid deficiencies before they start. This is especially true for specific growing conditions.
- Hydroponic and Coco Coir Systems: In soilless mediums, CalMag is required with every feeding. Coco coir has a high cation exchange capacity and can bind with calcium and magnesium, making them unavailable to the plant. Using reverse osmosis (RO) or distilled water also necessitates supplementation as these water types are devoid of minerals.
- Soft Tap Water: If your tap water has a low mineral content (soft water), regular CalMag application is recommended. Testing your water's electrical conductivity (EC) can help determine if it's soft.
- High-Demand Plants: Crops like tomatoes, peppers, and cannabis are known to be heavy feeders and often benefit from consistent CalMag supplementation throughout the vegetative and flowering stages.
Corrective Application
If you see symptoms of a deficiency, a corrective application is needed. Visual signs will depend on whether the plant needs calcium, magnesium, or both.
Symptoms of Calcium Deficiency
- Stunted growth and poor root development.
- Distorted or curling new leaves (often called "parachute leaves").
- Brown spots or tip burn on the edges of new growth.
- Blossom end rot in fruits like tomatoes.
Symptoms of Magnesium Deficiency
- Yellowing of older leaves, particularly between the veins (interveinal chlorosis).
- The yellowing starts on the bottom leaves and moves up the plant.
Comparison Table: When to Use CalMag
| Factor | Proactive Use (Preventative) | Corrective Use (Reactive) |
|---|---|---|
| Growing Medium | Coco coir, hydroponics, and other soilless mediums | Soil-based growing after a deficiency is confirmed |
| Water Type | Reverse Osmosis (RO), distilled, or soft tap water | Any water type when deficiency symptoms appear |
| Plant Stage | Throughout vegetative and early flowering stages | At any stage, from seedling onward, once a problem is diagnosed |
| Application | Regular, consistent dose with each feeding | Increased dose temporarily to fix the issue |
| Sign of Need | Knowledge of growing medium or water properties | Visible symptoms like yellowing leaves or blossom end rot |
How to Apply CalMag
Regardless of your growing system, proper application is key to success.
- Mixing: Always add your CalMag supplement to your water before adding other nutrients. This prevents potential nutrient lockout caused by imbalances. Give the solution a good stir to ensure even distribution.
- Dosage: Follow the manufacturer's recommended dosage as a starting point. For hydroponics and coco, a typical preventative dose is around 1-1.25 ml per liter, while a corrective dose might be slightly higher. Adjust based on your plant's response.
- pH Management: After adding CalMag, always check and adjust the pH of your nutrient solution. CalMag can affect pH, and an incorrect pH range will prevent plants from absorbing nutrients effectively. The ideal pH range is generally 5.5-6.5 for soilless systems and 6.0-7.0 for soil.
- Foliar Spray: For a rapid fix in severe deficiency cases, a diluted CalMag solution can be applied directly to the leaves. This provides a quick boost but is not a long-term solution. Foliar feeding is most effective when the lights are off to avoid burning the leaves.
- Flushing: Avoid nutrient buildup by regularly flushing your growing medium with plain water. This is particularly important when using corrective doses.
When to Stop or Taper Off CalMag
While essential for most of the growth cycle, CalMag should be tapered off towards the end of flowering. This final period is known as the flushing stage.
- Final Weeks of Bloom: As your plants approach harvest, typically 1 to 2 weeks out, you should stop or significantly reduce CalMag supplementation.
- Flavor and Smoothness: Reducing nutrients during the flush helps remove excess salts and minerals from the plant tissue. This prevents the final product from having a harsh taste.
- Monitoring: Pay close attention to your plants. If a deficiency reappears late in flower after cutting back, you can add a small, gentle dose. However, some deterioration of older fan leaves is normal as the plant directs its energy to the flowers.
Conclusion
Using CalMag is a necessary practice for many gardeners, especially those relying on soilless mediums or soft water sources. The key to successful supplementation is a proactive approach, regular monitoring, and careful attention to dosage and pH levels. By understanding when to use CalMag for both prevention and correction, you can avoid common deficiencies and ensure your plants remain healthy and vibrant throughout their entire life cycle, ultimately leading to a more successful and abundant harvest.
Visit Royal Queen Seeds for more detailed information on CalMag for cannabis plants.
