Gypsum 101

succulent_succotashJuly 9, 2013

I am a newbie gardener and need some help understanding gypsum in Al's Gritty Mix. My intention is to use the complete gritty mix in small pots for succulents. But, I'm sure this applies for all container gardening.

I bought all the ingredients for the gritty mix with the exception of gypsum.

Questions about Gypsum:
1. Is it absolutely necessary to add gypsum to the gritty mix?
2. Can you mix gypsum into the entire batch and let it sit? Or should I add on an need-more-soil basis? (I have a non-sifted 50lb bag of Turface, 75lb granite, 1.5cut ft bag of fir bark)
3. How often do you need to add gypsum to the gritty mix?
4. When "refreshing" soil, do you simply add to existing mix, or do you have to dump out old soil and replace with new mix with gypsum?
5. Do you have to use epsom salt in gritty mix, too?
6. What are some common brands of gypsum? Based on other threads: CalMag, B-1, Foliage Pro...


Here is the information I gathered from other threads to consolidate:

-1 tablespoon of gypsum per gallon of gritty mix
-Gypsum is Calcium Sulfate (CaSO4)
-It is not the same as Epsom salt (magnesium)
-It serves as a fertilizer in the gritty mix
-You can buy at select nurseries, big box stores, and, hydroponics stores
-Some may use Plaster of Paris as a substitute, but opinions are split on this


Definition: Gypsum is a mineral consisting of hydrous calcium sulfate that is used as a soil amendment to add sulfur and calcium and counteract salt damage. It is added to cement to regulate setting.


It is also used to loosen up stubborn, compacted or clay soils. Gypsum works by pulling together clay particles in the soil to make bigger particles, creating porous spaces for air, water and plant roots. For saline-infused soil, gypsum removes sodium and replaces it with calcium. For all soil types, gypsum adds calcium and sulphur, which are necessary elements for plant growth. Gypsum also helps soil retain water and helps decrease soil erosion.



Thank you :)

Thank you for reporting this comment. Undo
shazaam(NC 7B)

Here are answers to a several of your questions...

1. No. Gypsum is only necessary if your fertilizer doesn't supply calcium.
2. You can go ahead and mix the full batch and let it sit.
5. No. Like with gypsum, epsom salt is only necessary if your fertilizer doesn't supply magnesium.
6. Brands will probably vary regionally. Try the lawn fertilizer section at Lowes -- the bags will be big, but they're very affordable. Foliage-Pro isn't gypsum. It's a soluble fertilizer that provides all the macro and micronutrients (including calcium and magnesium).

    Bookmark   July 9, 2013 at 8:52PM
Thank you for reporting this comment. Undo
fireduck(10a) are on the right track. We are all doing science experiments...but often times these issues are not clearly defined scientific formulas. If you know what I mean....Certain potting ingredients (like bark and peat) make the mix acidic. Calcium neutralizes the acidity for plants not wanting an acidic medium. Hope this helps.

    Bookmark   July 10, 2013 at 12:27PM
Thank you for reporting this comment. Undo
shazaam(NC 7B)

While what fireduck says is true with regard to adding lime to the 5-1-1 (bark/peat/perlite) mix, it doesn't apply to the gritty mix (turface/granite/bark). Al's gritty mix has a pH that's suitable for most plants, which is why he uses gypsum (a calcium source that, in this context, doesn't affect pH) rather than lime (a calcium source that raises pH).

    Bookmark   July 10, 2013 at 1:21PM
Sign Up to comment
More Discussions
Help! My kumqat is dying
Hello everyone, I am hoping to get some help related...
Need help!..white spots on my lemon seedlings!!
I recently found white spots on the leaves of my lemon...
Kavitha Raghunath
Long Term Potting Mix Recipe - Alternative to Gritty Mix
Hi everyone, I'm a new gardener from Perth, Western...
Avocado as a Container Plant III
Well, another wonderful Summer is passing, and there...
greenman28 NorCal 7b/8a
PVC liner OK for growing food?
A contractor friend of mine made me a planter box to...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™