Calcium Magnesium Questions

[SundayGardener]

Hello,
Thanks to the helpful experienced orchid experts, I discovered that I needed to add cal mag when using distilled water, especially for cattleyas.

I'm able to get RAW Cal Mag locally, but it seems pricey. Searching around, it seems Peters Excel Cal Mag 15-5-15 is popular (but not necessarily easy to get?). My question is, is this used in place of a fertilizer, or in addition to fertilizer? My impression is in place of a fertilizer, in which case, my next questions are is it a good fertilizer for orchids (aside from the cal mag) and should it be avoided for paphs and other calcium sensitive plants? I think I saw in another thread that H&R nurseries uses it, but I believe they grow mainly catts and dens, and species (but not paphs?).

Finally, has anyone ever just used powdered calcium and magnesium? For instance NOW Foods label sells both in a powder as a human supplement.

Then there is the amount. RAW Cal Mag says 1/8 tsp per gallon, but I don't think this is enough for catts. I've seen improvement but still think I see signs of calcium deficiency and I've been supplementing for 6 or 8 weeks now, or longer. I use it for all waterings, although now I'm using up 1/4 tsp for catts and encyclias only.

Thanks for any input! I'd really love to get at least one cattleya bloom this year

[Optimist]

I'm using K-Lite orchid and epiphyte fertilizer which has calcium and magnesium in it. It's worth the cost because it means less guesswork, less buying of multiple products, etc.

I actually had no idea that Paphs were calcium sensitive. I will have to look that up. From what I have seen many of the strap leaf types live as lithophytes, and also the SE Asia types usually live over limestone caves and outcroppings, meaning they live in close proximity to a lot of Calcium.

What is your take on what calcium deficiency looks like?

You could use bone meal on orchids-- it has a tendency to mold though. Better yet there is chicken oyster shells used by chickens to develop better egg shells. It's basically a 5 lb bag of crushed oyster shell (sanitized). You buy it at a farm store like Tractor Supply. I put a loose sprinkle on my orchids (cattleyas and paphs) twice a year.

I hope you get some flowers too! Good luck!

[Roberta]

In powder form, Ca and Mg have to be combined with something else. The "what else" will identify the conditions under which it is soluble. If it is designed to dissolve in stomach acid, it will be pretty insoluble in water. If your tap water is "hard" - containing calcium and magnesium carbonates, have you considered just mixing some tap water in with your pure water? The average amounts of those minerals in your tap water should be available from your water company.

[Dollythehun]

I hesitate to stick my toe into this water (pun intended). My water is very hard. (I filter it or use rain water now). It binds up the calcium and magnesium and my phals eventually showed symptoms, as did one of my Catts. I was advised to put eggshells in my Catt medium, and I switched to a monthly Cal mag supplement from Amazon. Once in awhile a symptom will arise and I give the plants a shot of epsom salts. That usually takes care of the problem. I don't have a scientific formula for this, I go by instinct and it's working.

Others will have a formula for you.

[Ray]

All plants need a steady supply of calcium while they are actively growing. Unlike most other minerals, calcium is not easily translocated within plant tissues, so if the plant is deficient in calcium, the newest growth, usually the tips if the leaves, or in the case of sympodial plants like cattleyas, the tips of newly growing pseudobulbs, will die and turn black, which is often mistaken for a fungal rot.

I have no scientific basis for this, but it appears (from reading fertilizer labels) that the proper amount of calcium is somewhere around 50% or more of the nitrogen concentration. K-Lite, for example, has 12.9% nitrogen and 10% calcium, while MSURO has the same nitrogen levels and 8% calcium.

Magnesium can be shared among plant tissues, so adding a tablespoon per gallon once a month is sufficient.

Most water supplies provide a sufficient level of both, so supplements are unnecessary.

[SundayGardener]

Thanks everyone!

My water is really hard. There is a lot of limestone in the area and it comes through the water supply. It leaves white deposits on everything. It's also pretty heavily chlorinated. We also have a water softener (although I'm not convinced it does anything) so that's also a potential problem for orchids. Anyway, I can always tell when I travel because the "foreign" water is so much easier on hair and skin.

I did start out using tap water, then spring water.

What I think are signs of calcium deficiency are purpling leaves and black spots of leaves (cattleyas only). I read the St. Augustine articles on calcium and cattleyas (here's one of the links:
https://staugorchidsociety.org/PDF/C...ySueBottom.pdf
.

I do use K-Lite. I think there is information on paph sensitivity to calcium on the slipperorchid.org, with a list. I DO have either oyster or crab shell on hand--ready for all contingencies!--so I'll try that! I bet I can get my hands on chicken oyster shells as well at the same place where I got cherrystone to make "gritty mix" for potting succulents and such.

[Dollythehun]

Is it possible for you to catch rainwater? Our members have several ingenious methods for doing that and storing it.

[Ray]

Originally Posted by SundayGardener

Thanks everyone!

My water is really hard. There is a lot of limestone in the area and it comes through the water supply. It leaves white deposits on everything. It's also pretty heavily chlorinated. We also have a water softener (although I'm not convinced it does anything) so that's also a potential problem for orchids. Anyway, I can always tell when I travel because the "foreign" water is so much easier on hair and skin.

I did start out using tap water, then spring water.

What I think are signs of calcium deficiency are purpling leaves and black spots of leaves (cattleyas only). I read the St. Augustine articles on calcium and cattleyas (here's one of the links:
https://staugorchidsociety.org/PDF/C...ySueBottom.pdf
.

I do use K-Lite. I think there is information on paph sensitivity to calcium on the slipperorchid.org, with a list. I DO have either oyster or crab shell on hand--ready for all contingencies!--so I'll try that! I bet I can get my hands on chicken oyster shells as well at the same place where I got cherrystone to make "gritty mix" for potting succulents and such.

Do not use softened water on your plants.

If your water is hard, and you use K-Lite, DO NOT add any of the other supplements.

[Orchid Whisperer]

Sunday Gardener:

If you have hard water, it is likely that you have enough calcium and magnesium in your water and do not need CalMag at all. Ask your local water utility if they have a complete analysis of your city tap water. That provides a lot of useful information on nutrients and macronutrients that you can safely omit from your plant's nutritional supplementation.

I would avoid using crab she'll on any plants that you may want to bring indoors. There is a lot of organic matter in the shell, and they will stink like dead sea creatures. Cleaned oyster and clam shells may be ok. You may not need the shell material in any case.

To avoid using softened water, try taking water for your orchids from any hose bibb outside your house. If your plumbing was done properly, the hose bibbs should tap into pre-softener water, rather than after. If you feel that it is necessary to reduce the hardness and dissolved solids, you can mix rain water or distilled water with your city water.

[SundayGardener]

OK, so with K-Lite, I don't add additional cal mag (or anything else).

We do have softened water, it is supposed to be just the hot water that is softened. Our water is high in calcium (54 mg/L) magnesium (32 mg/L), iron and manganese. Water hardness is 265 mg/L, total inorganic solids 300 mg/L. That's from the city. From the tap may be different, given the age of the plumbing and construction activity which causes interesting things to happen with the water.

I only have one orchid outside. I know the wisdom of putting them outside. However, "walk aways" are common in my area and I'm also losing my annual war with the japanese asian beetles and they are relentless. I'm plotting some sort of screened in, not easily accessible solution.