Botanicare Cal-Mag Plus – Quart

Botanicare Cal-Mag Plus is a highly fortified calcium, magnesium and iron plant supplement formulated to correct common nutrient deficiencies. It is especially useful when working with reverse osmosis water or growing in coco coir media, where natural calcium draw can leave plants deficient. The quart size delivers a practical volume for home and small commercial growers, and the liquid concentrate can be added to your nutrient program or applied directly as a foliar spray.

Cal-Mag Plus Specifications

Specifications below are drawn from the canonical product data. The weight figure is the shipping weight for the quart bottle.

Why Choose Cal-Mag Plus

Calcium and magnesium deficiencies are among the most common problems growers encounter, particularly in hydroponic and coco coir systems. Cal-Mag Plus addresses this directly with a fortified liquid formula that delivers three essential elements — calcium, magnesium and iron — that are frequently missing or locked out in purified water systems or high-calcium-demand media.

• Formulated for RO water users: Reverse osmosis filtration strips virtually all minerals from water. Cal-Mag Plus is specifically recommended to rebuild the calcium and magnesium baseline before adding your primary nutrient program, helping avoid mid-cycle deficiencies that affect yield and quality.
• Addresses coco coir’s calcium draw: Coco coir has a well-known tendency to bind calcium, making it unavailable to plant roots. Supplementing with Cal-Mag Plus compensates for this natural draw without requiring a full media replacement.
• Iron inclusion: Many basic cal-mag products stop at calcium and magnesium. Cal-Mag Plus includes iron, which supports chlorophyll production and reduces the risk of interveinal chlorosis that can stall plant growth.
• Foliar application option: For fast-acting correction of visible deficiency symptoms, Cal-Mag Plus can be diluted and sprayed directly onto foliage. This provides a quicker uptake pathway than root-zone feeding alone when symptoms are acute.
• Compatible with existing programs: The product is designed to supplement — not replace — your current nutrient line. It can be added to most hydroponic, coco, and soil feeding programs without reformulating the rest of your schedule.

Best Uses for Cal-Mag Plus

Cal-Mag Plus is a broadly applicable supplement, but it delivers the most consistent benefit in specific growing scenarios where calcium and magnesium availability are structurally limited by the water source or growing medium.

• Hydroponic systems using reverse osmosis water: RO water has near-zero mineral content. Adding Cal-Mag Plus before your base nutrients helps establish the calcium and magnesium levels plants expect, preventing early deficiency symptoms in the root zone.
• Coco coir grows: Whether running a full coco medium or a coco-blend substrate, the medium’s natural cation exchange characteristics make calcium supplementation an ongoing necessity rather than an occasional fix. Cal-Mag Plus integrates cleanly into weekly feeding schedules.
• Correcting deficiency symptoms mid-cycle: When plants show classic calcium deficiency signs — brown leaf tips, stunted new growth, blossom end rot in fruiting crops — Cal-Mag Plus can be applied via root drench or foliar spray to begin correcting the imbalance quickly. For products to support overall nutrient health, consider pairing with Earth Juice Hi-Brix Molasses as a complementary biological amendment.
• Soft water regions: Growers in areas where municipal water supply is naturally soft (low dissolved minerals) benefit from calcium and magnesium supplementation even without using RO filtration.
• Seedling and clone programs: Young plants with limited root systems benefit from having calcium and magnesium readily available in the nutrient solution at appropriate rates for the growth stage.
• Foliar recovery applications: Spraying diluted Cal-Mag Plus directly on leaves provides a quick corrective dose when plants show interveinal chlorosis or other visible deficiency signs that need faster correction than root feeding alone can provide.

Compatibility

Cal-Mag Plus is designed as a supplement to your existing nutrient program and is broadly compatible with hydroponic, coco coir, and soil growing systems. It can be used alongside most base nutrient lines. Always mix Cal-Mag Plus into your reservoir or foliar spray tank before adding other concentrated nutrients to avoid precipitation or pH swings. When mixing with other additives, verify the final pH is in range (typically 5.5–6.5 for hydroponics, 6.0–7.0 for soil) after all products are combined.

For growers running biological programs or microbial additives alongside their nutrient program, Cal-Mag Plus is compatible with most beneficial microorganism products. If you are using a product such as Advanced Nutrients Tarantula to boost root-zone microbiology, add Cal-Mag Plus to your reservoir feed separately from any live microbial inoculants to minimize contact time between concentrated nutrients and live organisms before dilution.

Manufacturer-published compatibility data and detailed mixing instructions are available via the Hawthorne Garden Company website (see Sources below).

Sources & Further Reading