Keep your plants productive and green in any growing medium with our top-quality calcium-magnesium supplement.

  • Guards against deficiencies in the growing medium
  • Supports your plants in vibrant growth
  • Helps plants bloom and develop weighty, quality harvests

What is Cal-Mag?
Under normal growing conditions, the core Emerald Harvest product line supplies ample calcium. Our calcium-magnesium supplement supports plants grown in coco coir and other holding mediums, guarding them against calcium or magnesium deficiencies. It also helps plants grow extensive root systems that can reach and absorb the required amounts of nutrients for vibrant growth. So, any garden can benefit from Cal-Mag.

Why purchase ours?
There are numerous cal-mag-type products on the market. The main difference with Emerald Harvest Cal-Mag:

  • formulated from the highest-quality ingredients – high-quality minerals mean low or no heavy metals or impurities
  • contains kelp for rapid growth and increased quality
  • works in harmony with the rest of the Emerald Harvest line – a perfect balance of the right nutrients without overfeeding

PLUS: Deficiencies might occur when growers use a competitor’s base nutrient or supplement in combination with Emerald Harvest products, misbalancing the concentrations and ratios of other essential nutrients.

Calcium (Ca) in Cal-Mag 

  • Essential for growth and plant tissue strength
  • Aids in cell formation & strengthens cell walls
  • Regulates transport of other nutrients
  • Activates certain enzymes & phytohormones
  • Supports Nitrogen utilization
  • Guards against Nutrient Deficiencies

Magnesium (Mg) in Cal-Mag 

  • Forms the central atom of chlorophyll
  • Helps plants utilize Phosphorous (P) & Iron (Fe)
  • is important for certain enzyme processes like photosynthesis and respiration


  • Only Emerald Harvest Cal-Mag contains Kelp – a sea algae
  • Kelp is known as nature’s fastest-growing “plant”
  • delivers auxins which stimulate plant and root-tip growth
  • provides cytokinins to make plants bushier and help preserve quality after harvest
  • has other phytohormones and biocatalytic effects
  • the aminos in kelp also function as chelators for optimal nutrient uptake

Feature Sheet