Emerald Harvest Cal-Mag, 55 gal

Calcium-Magnesium Supplement with Kelp for Any Growing Medium, 55 Gal

Fast-draining media like coco coir and soilless mixes flush calcium and magnesium out of the root zone faster than a standard base nutrient replaces them, which is where deficiency symptoms tend to show up first. Emerald Harvest Cal-Mag is a calcium-magnesium supplement built with kelp to close that gap in any growing medium, not just coco. Calcium supports cell wall structure and new tissue development, while magnesium sits at the center of the chlorophyll molecule and drives the enzyme activity involved in nutrient uptake. Kelp contributes naturally occurring plant compounds that complement the mineral supply rather than replacing it.

The 55-gallon size is built for commercial coco and soilless operations that supplement calcium and magnesium on every feeding.

Key Features & Benefits

• Calcium and magnesium supplement — targets the two secondary macronutrients most prone to deficiency in fast-draining media.
• Kelp-derived additive — naturally occurring plant compounds complement the mineral supply.
• Reduces deficiency risk in coco coir — coco's fast drainage and cation exchange behavior flush cal-mag faster than many base nutrients replace it.
• Magnesium for chlorophyll and enzyme activity — supports light capture and the enzymatic processes involved in nutrient uptake.
• Works with any base nutrient — layers onto Grow/Micro/Bloom, Cali Pro, or any other feeding program.

Who Should Use Cal-Mag

Cal-Mag fits any grower running coco coir, rockwool, or another fast-draining soilless medium where calcium and magnesium deficiency is common. It's also useful in soil-based programs using RO or soft water that carries little natural calcium or magnesium.

About Emerald Harvest Cal-Mag

Emerald Harvest, based in Santa Rosa, California, added Cal-Mag as a supplement rather than one of its original three-part base formulas, aimed specifically at the gap that shows up most often in coco coir and other soilless media.

Frequently Asked Questions

Why does coco coir need cal-mag supplementation?

Coco coir's cation exchange behavior binds calcium and magnesium out of solution more readily than soil does, and its fast drainage carries unused nutrients out of the root zone quickly. A standard base nutrient often doesn't replace calcium and magnesium fast enough to keep pace, which is where a dedicated cal-mag supplement fills the gap.

What deficiency symptoms does Cal-Mag address?

Calcium deficiency typically shows up as distorted new growth or weak cell walls, while magnesium deficiency appears as interveinal chlorosis — yellowing between the leaf veins while the veins stay green. Cal-Mag supplies both minerals together since the two deficiencies often overlap.

How is Cal-Mag added to a feeding schedule?

Add it to the reservoir or feeding solution alongside your base nutrient at every feeding, or on the schedule your growing medium requires. Coco coir and rockwool typically need it more consistently than soil.

Does Cal-Mag work with base nutrients other than Emerald Harvest's own line?

Yes, it's formulated to supplement any base nutrient program, not just Emerald Harvest's Grow/Micro/Bloom or Cali Pro lines. Follow label rates since dosage can vary depending on how much calcium and magnesium your base formula already supplies.

What does the kelp in Cal-Mag contribute?

Kelp adds naturally occurring plant compounds that complement the calcium and magnesium supply rather than replacing it. It's included as a supporting ingredient in the same bottle rather than as a separate additive.