Roots Organics CalMag – 1 Quart

Roots Organics CalMag is a liquid calcium, magnesium, and sulfur supplement derived from natural mineral sources — Kieserite and Gypsum. It is formulated without added nitrogen, phosphate, or potassium, giving growers precise control over secondary nutrient supplementation without shifting the primary fertility ratios already dialed in through a base fertilizer program. It is designed for fast-growing, heavy-feeding plants and is recommended for use alongside base nutrients like Roots Organics Buddha Grow and Buddha Bloom.

Roots Organics CalMag – 1 Quart Specifications

The table below summarizes the key product specifications drawn from the manufacturer’s product information and shipping data.

Specification	Value
Brand	Roots Organics
Product Name	CalMag
Size	1 Quart (32 fl oz / approximately 946 mL)
Formulation Type	Liquid concentrate
Primary Mineral Inputs	Calcium, Magnesium, Sulfur
Derived From	Kieserite, Gypsum
Added N-P-K	None (free of added nitrogen, phosphate, and potassium)
Shipping Weight	6.0 lb

Why Choose Roots Organics CalMag

Calcium and magnesium deficiencies are among the most common secondary nutrient problems in controlled-environment growing, particularly in systems that rely on reverse osmosis water, coco coir, or high-frequency fertigation. Most CalMag products on the market include significant amounts of nitrogen, which can make it difficult to supplement secondary nutrients without also pushing nitrogen levels beyond the target. Roots Organics CalMag is built around a different formulation approach: it supplies calcium, magnesium, and sulfur without adding any nitrogen, phosphate, or potassium to the mix.

This means you can use CalMag as a targeted corrective tool throughout the entire crop cycle — including late bloom, when most growers want to reduce nitrogen input — without being forced to work around excess primary nutrient loading. The product derives its calcium and magnesium from Kieserite and Gypsum, both naturally occurring mineral sources with established use in organic and conventional agriculture.

It integrates cleanly into the Roots Organics nutrient program, where it is specifically recommended for use alongside Buddha Grow and Buddha Bloom base fertilizers. Growers running those programs can add CalMag to the reservoir at any stage without recalculating their primary NPK targets. Growers on other base programs will find the nitrogen-free formulation equally useful for the same reason.

• Provides calcium, magnesium, and sulfur without any nitrogen, phosphate, or potassium — useful at all growth stages, including late bloom
• Derived from natural mineral sources (Kieserite and Gypsum) rather than synthetic chelates
• Maintains existing base fertilizer NPK ratios when added to an established program
• Suited for fast-growing and heavy-feeding plant varieties that consume secondary nutrients more rapidly
• Recommended pairing with Roots Organics Buddha Grow and Buddha Bloom for a complete nutrient program

Best Uses for Roots Organics CalMag

CalMag is a supplemental product used to address or prevent secondary nutrient deficiencies. The following scenarios represent the most common use cases based on the product’s formulation and category.

• RO and soft-water feeding programs: Reverse osmosis water strips out naturally occurring calcium and magnesium. Growers running RO systems typically need to add back these minerals before mixing nutrients, and a nitrogen-free CalMag source makes that straightforward without affecting NPK ratios.
• Coco coir cultivation: Coco is known to bind and hold calcium ions, which increases the plant’s calcium demand. Supplementing with a dedicated calcium and magnesium product is standard practice in coco grows, and the absence of added nitrogen in this formulation gives growers flexibility across the whole schedule.
• Fast vegetative growth: During periods of rapid shoot and leaf expansion, plants draw on secondary nutrients at a higher rate. Adding CalMag to the reservoir during the vegetative stage supports cell wall development and chlorophyll synthesis.
• Heavy-fruiting and late-bloom cycles: Plants pushing large, dense fruiting bodies need reliable calcium availability for cell division and structural integrity. Since this product contains no nitrogen, it can be added during late bloom without interfering with the standard late-cycle nitrogen reduction strategy.
• Correcting visible deficiency symptoms: Interveinal chlorosis (often a magnesium deficiency) and blossom end rot or tip burn (often linked to calcium deficiency or uptake issues) are among the early signs that CalMag supplementation may help. Apply as a soil drench or reservoir addition at the first sign of deficiency.
• Pairing with Roots Organics base nutrients: The product is specifically designed to complement Buddha Grow and Buddha Bloom, making it a natural fit for growers already using the Roots Organics line.

Roots Organics CalMag vs Similar Products

The CalMag category is crowded with products that bundle calcium and magnesium with nitrogen. These formulations typically carry an NPK of around 2-0-0 or higher, meaning that every milliliter of CalMag you add also adds a measurable amount of nitrogen to the reservoir. For many growers, this creates a tradeoff: correct the deficiency and accept elevated nitrogen, or hold back on CalMag to control nitrogen and risk letting the deficiency worsen.

Roots Organics CalMag avoids this tradeoff by delivering calcium, magnesium, and sulfur without any added N, P, or K. Growers using nitrogen-bearing CalMag alternatives during late bloom often have to reduce their base nutrient dose to compensate — a workaround that adds complexity and can cause its own imbalances. With a nitrogen-free formulation, the secondary nutrient supplement does not interfere with the primary nutrient program, and dose adjustments to the base fertilizer are not required.

The mineral source is also relevant. Kieserite is a naturally occurring hydrated magnesium sulfate mineral, and Gypsum is a naturally occurring calcium sulfate mineral. Both have a long record of use in organic agriculture. Growers preferring naturally derived inputs over synthetically chelated mineral compounds may find this formulation more consistent with their program goals.

For growers looking to pair CalMag with a biological root inoculant, Advanced Nutrients Tarantula is a microbial root enhancer that works alongside supplemental mineral programs in the same Nutrients & Additives category.

Compatibility

Roots Organics CalMag is a liquid concentrate designed to be added to the nutrient reservoir or mixed into water for soil or media application. The following notes cover the most common compatibility considerations based on the product’s formulation.

Growing media: Compatible with all standard growing media including soil, coco coir, perlite, rockwool, and hydroponic or aeroponic systems. Particularly well-suited to coco coir and hydroponic applications where natural calcium and magnesium are absent from the growing medium.

Water source: Appropriate for use with RO water, soft municipal water, and well water. Growers using hard water with significant existing calcium and magnesium levels should test their source water before adding CalMag to avoid excess mineral accumulation.

Nutrient programs: Designed specifically to integrate with the Roots Organics Buddha Grow and Buddha Bloom base fertilizers. The nitrogen-free formulation means it is also compatible with most other base nutrient programs without requiring NPK ratio adjustments. It is generally added before or after the base nutrients are mixed, with thorough agitation between additions.

pH range: As with all liquid nutrient supplements, the final pH of the solution should be verified after mixing. Target pH is typically 5.8–6.2 for hydroponic systems and 6.0–6.8 for soil and coco applications. Adjust pH after all nutrients are added and the solution is fully mixed.

For growers running a complete soil-health-focused program, Earth Juice Hi-Brix Molasses is a carbohydrate supplement in the same product category that pairs well with organic mineral inputs.

Dosing Guidelines

Roots Organics CalMag is a liquid concentrate. General dosing guidance for nutrient supplements of this type follows the standard practice outlined in the Roots Organics nutrient program documentation. Always shake or stir the bottle thoroughly before measuring, as natural mineral formulations can settle.

General starting point: Typical use rates for liquid CalMag supplements in this category range from 1–5 mL per gallon of water, adjusted based on plant size, growth stage, media type, and source water mineral content. Begin at the lower end of the recommended range and increase based on plant response and runoff EC readings.

Vegetative stage: Start at the low end of the dose range and monitor new growth for signs of calcium or magnesium deficiency (yellowing between leaf veins is a common early magnesium indicator; tip burn or spotting can indicate calcium issues). Increase incrementally if symptoms appear.

Bloom and fruiting stage: Calcium demand often increases during heavy fruit set and development. Because this product contains no nitrogen, the dose can be maintained or increased during late bloom without concern about excess nitrogen interfering with ripening. Check EC after adding CalMag and adjust base nutrient dose if total EC exceeds the target range.

Corrective application: For visible deficiency symptoms, apply at the upper end of the recommended range for 1–2 feedings, then assess plant response before adjusting further. Foliar application of diluted CalMag solution can accelerate correction of visible leaf symptoms, though root-zone supplementation is the primary delivery method.

EC and testing: After mixing nutrients and CalMag together, verify EC is within the target range for the current growth stage before irrigating. Adjust the base nutrient dose, not the CalMag dose, if EC runs high — since the primary goal of CalMag is to address a specific mineral gap, hold the CalMag dose steady when possible.

For specific dose tables and mixing schedules when using CalMag alongside the full Roots Organics line, refer to the nutrient schedule published on the manufacturer’s website.

How to Use Roots Organics CalMag

The steps below describe standard procedure for incorporating a liquid CalMag supplement into a hydroponic reservoir or hand-watering program. Specific dose rates are found on the product label and in the Roots Organics feed chart.

1. Shake the bottle thoroughly. Natural mineral formulations can settle during storage. Invert and shake well before each use to ensure an even, consistent mixture.
2. Measure your water volume. Determine the total gallons or liters in your reservoir or watering can before adding any nutrients. Accurate water volume is the basis for all dose calculations.
3. Fill reservoir or container with your water source. Start with fresh RO, soft, or otherwise pre-treated water as required for your system. If using a recirculating reservoir, note the existing EC and mineral content before adding new nutrients.
4. Add CalMag first (if using with other nutrients). When combining multiple liquid nutrients, add CalMag to the water before adding base nutrient concentrates. This helps prevent potential precipitation that can occur when concentrated calcium solutions contact concentrated phosphate or sulfate solutions directly.
5. Add base nutrients and any other additives. Follow the Roots Organics feed chart or your own program schedule. Mix thoroughly between each addition.
6. Check and adjust EC. After all inputs are added, test the electrical conductivity of the solution with a calibrated EC meter. Verify it falls within the target range for the current growth stage.
7. Check and adjust pH. After mixing, test solution pH and adjust to 5.8–6.2 for hydroponics or 6.0–6.8 for soil and coco. Always adjust pH last, after all nutrients are fully mixed.
8. Apply to plants and observe response. Irrigate as usual. Within a few feedings, monitor new growth for improvement in any deficiency symptoms. Adjust dose for the next feeding based on plant response.

If running a multi-part program, Heavy 16 Roots is a root development supplement in the same Nutrients & Additives category that some growers pair with secondary mineral supplements during early establishment.

Sources & Further Reading