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DIY Cal-Mag Recipe

Heather has been showing signs of a beginning magnesium deficiency. You can spot a magnesium deficiency when the fleshy part of your leaves turns yellow, but the veins of the leaves stay dark green. (Shout out to @str8outthepot for helping me with this!)


Heather's bright yellow leaves and green veins indicate a magnesium deficiency.

If you follow the #GrowLikeChef grow guide, you know that we use advanced Nutrients Cal-Mag, which contains both calcium and magnesium. These two nutrients are often paired together because they help eachother out. Plants eat up magnesium quickly and easily, but not calcium. So if you give your plant magnesium alone, you run the risk of burning the plant if it takes in too much. On the other hand, calcium is absorbed quite slowly by your plants. When you pair them together, the magnesium helps your plant take in more calcium, and the calcium helps slow down the absorption of magnesium. Essentially, they regulate each other.


Instead of using a bottled nutrient to fix this problem, I'm using a recipe to make my own Cal-mag at home. It's really cheap and easy, but this process does last a couple of days so try to make it in advance if you can so you always have it ready.


Essentially, you’re going to boil egg shells and Epsom salts in a gallon of water, then strain it out. The egg shells seep calcium into the water, providing your cal. Epsom salts are made of magnesium sulfide, which provide the mag part of your cal-mag. When you boil all of these together, they create a nutrient dense water that you can add to your plants for a boost.


The green color is returning to her leaves after I watered her with the cal-mag solution.

And this formula really works! I watered Heather with 2 cups of this cal-mag mixture and 4 days later she was back to turning dark green and lush. I’m so happy with how fast this formula turned her deficiency around.


So here’s the recipe!

You'll need:

6 large eggs

Epsom Salts

1 Gallon Water

Large stock pot with a lid

Super simple - only 3 ingredients

1. Crack all of your eggs and rinse out the shells. Leave the washed shells out to dry overnight.

2. The next day, take a rolling pin and crush your dried eggshells into small pieces.

3. Weigh your crushed eggshells with a kitchen scale. This recipe calls for 30 grams of dried egg shells. Discard any extras.

4. Measure out 15g of epsom salts.

5. Take your large stock pot, add 1 gallon of water, 30g of dried eggshells and 15g of Epsom Salts. Place on your stovetop and turn your burner to high. Bring this mixture up to a boil and keep it boiling for about 5 minutes.

6. After a few minutes, turn off your burner and cover your pot with the lid. Let this sit for at least 24 hours. The eggshells and epsom salts will release their nutrients into the water during this time.

7. Strain any eggshells or debris out of the mixture.

8. Water your plant with 2 cups of this mixture to give your plant a boost of calcium, magnesium and sulfur. This recipe makes 1 gallon of cal-mag booster, which is enough for 8 treatments. Store the remaining to use later.


This recipe was made by combining these two DIY tutorials: Wikihow & SFGate

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