EH Cal-Mag - Quart - Case of 12Grow Lush, Green Plants Keep your plants productive and green in any growing medium with Cal Mag, a calcium and magnesium supplement from Emerald Harvest. Emerald Harvest Cal Mag is more than just a calcium magnesium supplement. In contrast to competing products, EH Cal Mag contains kelp extract, a natural source of nitrogen and other helpful compounds, making it different from standard products of its kind. Containing top quality ingredients, Cal Mag