Emerald Harvest - Cal-Mag


Size: 0.95 Litre
Sale price£19.99

Boosts Photosynthesis Rates and Nutrient Transport for Enhanced Growth

Cal-Mag, from California's Emerald Harvest, maintains optimal growth rates by providing a source of calcium and magnesium - two secondary macro nutrients that play hugely important roles in plant health. Cal-Mag will assist with the transport of other nutrients and increase photosynthesis rates, while helping to get the best out of your other boosters during peak flower. Essential stuff! For more information take a look at our Emerald Harvest Blog.

How Cal-Mag Works

Cal-Mag delivers a rich source of calcium and magnesium, two secondary macronutrients that are essential for plant health and vitality. If plants don't get an adequate supply of calcium and magnesium, then you'll start to notice some very negative consequences. Growth can slow down to a crawl and you'll see clear signs of deficiencies, like yellowing between the veins on leaves (magnesium) and dark brown spots (calcium), as well as an overall paleness.

Cal-Mag is particularly useful for growers who live in soft water areas. Soft water has lower levels of dissolved minerals, resulting in lower starting EC levels. The dissolved minerals in tap water tend to be made up of a large proportion of calcium and magnesium, which makes it all the more important for those in soft water areas to supplement with Cal-Mag.

But it's not just those in soft water areas who need to pay attention. High levels of potassium can lock out calcium and magnesium. Potassium is needed in larger amounts during the bloom phase, which is great for flowers and fruits, but it can also trigger deficiencies if you don't keep an eye on it. This is also worth noting for those running coco coir - one of the UK's most popular mediums. Coco naturally releases excess potassium as it degrades, which can trigger issues with nutrient lockout. Cal-Mag is exactly what you need to keep you growing sweetly.



1 x bottle of Emerald Harvest Cal-Mag. Choose from the following sizes: 0.95 litre, 1.89 litre, 3.79 litre


  • Part of the Emerald Harvest range - California's finest
  • Brings the best out of your other nutrients, especially PK boosters
  • Maintains optimal plant growth
  • Particularly important for those in soft water areas (with low levels of calcium and magnesium)
  • Encourages cell division and strengthens cell walls (calcium)
  • Activates enzymes required to increase growth rates, while assisting in protein synthesis (magnesium)
  • Formulated after years of research and development
  • Brings the best out of coco coir (or any situation where there's an excess of potassium)
  • Produces amazing results in any grow medium or system

How To Use

How to Use Cal-Mag

Add Cal-Mag to your reservoir at rate of 1.3ml per litre of nutrient solution. Start using Cal-Mag once your seedlings and cuttings are properly rooted and keep using it until week 6 of flower (assuming you are on a 9 week cycle). Never pre-mix nutrients - always fill the reservoir first and then add nutrients, stirring vigorously each time. A copy of the Emerald Harvest feedchart can be found by clicking the link below this description.

As with all nutrients, boosters and additives, never mix them together in their concentrated form (i.e. straight out of the bottle). Always add each nutrient, booster or additive to your reservoir or feed water in turn, giving the solution a good stir to mix it in before adding the next one.

Cal-Mag is highly effective in any growing medium or system. The ideal pH range after mixing nutrients is 5.8 to 6.3. Keep water temperatures between 18° and 21°, using a chiller, if necessary.

Guaranteed analysis: 2-0-0

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