How to use eggshells for calcium supplement in potting mix?

[Dr. Dave 4u]

First, I wish to thank everyone who has responded to my beginner questions....it's been very helpful...thanks again!

OK, I'm asking about using eggshells for indoor orchids.

I have been watching some videos and searching the posts on here about using egg shells for a mineral supplement. I kind of like the idea to recycle them but is it really a good idea?

My questions are as follows....

- If they are from hard boiled eggs they would be sterilized, correct?- Some folk recommend*you bake the shells at 300 for about 20 min, is this necessary?

- What about the membranes on the inside of the shell....would they cause problems with any indoor pests, bugs, FUNGUS GNATS etc? If so, the best way to remove the membranes?

- Some say grind them coarsely with mortar and pestle and work into your potting mix, some say grind to fine powder in spice grinder and shake on a few times per year. I assume the coarser grind would hold more in the potting mix and the powder wash through? Thoughts?

- How much eggshell per orchid would be good to use?
Say in a quart of orchid mix how many Tbsp's would you suggest?

[Mr.Fakename]

What orchids do you intend on using the eggshells on?

If your fertiliser solution is already balanced and the plants don't need a calcium boost, there's no reason torturing yourself with so many questions!

[estación seca]

Egg shells have been suggested for years but they don't really provide extra calcium unless you use very acidic water. Calcium has low solubility in water. The protein in the shell feeds soil organisms, which can be beneficial. Also eggshells in your pots attract attacks by fungus gnats, cats and dogs.

[Dr. Dave 4u]

I'm glad I asked first, seems the eggshell thing is more of a "growth rumor" than actual fact.
I was not even sure which orchids to use it on.
I do have a balanced urea free orchid fertilizer which should be fine.
Thanks

[Ray]

Dr. Dave - first of all, what makes you think you need to add calcium? Most water supplies have plenty, but that depends upon your water source - collected rainwater, snow melt, reverse osmosis system, well, or municipal supply.

Where do you live? Have you checked with your municipal water provider (if applicable)?

Then, after that, if you DO need to add calcium, it can better be handled through selection of fertili9zer or additives. As was stated above, eggshell is not particularly water soluble.

Take a look at THIS.

[Dr. Dave 4u]

Hi Ray,
Your right, I never checked the calcium in my water supply. I think my water is pretty hard so probably have enough.
I am currently using Sun Bulb Company 8303 Better Gro Orchid Plus 20-14-13 mildly diluted.
I had seen some youtube videos, by amateurs of course, stating how they get their orchids to bloom again sooner by using eggshells for calcium supplementation. Of course one does not know how deficient their watering water is. Also could be their imagination, maybe they are doing all the other things correctly and thus happy blooming orchid?!!
I think someone started the eggshell myth as if its a magic bloomer formula for all orchids all times. Now that you got me doing some critical thinking I of course see the fallacy in this.
Please excuse my ignorance as I am new to this hobby.
As a side note this reminds me when I was actively seeing patients they would tell me some miracle thing/product they used for some great benefit. Then I'd ask some questions to find out that they had changed their lifestyle in many ways that could be benefiting them but they paid total homage to the miraculous product and not the lifestyle changes!!
Human nature and lack of critical thinking I guess.....

[Ray]

Dr. Dave - the way you’re asking questions rather than blindly jumping into doing things says a lot of good things, in my mind.

Of course, you Did jump into orchid growing, and that’s going to “dog” you for the rest of your life! (Just like the rest of us.)

[Dr. Dave 4u]

Help me Ray!!!! Help me.........

I just boosted US economy by dropping some bucks on more orchids!!

I am running out of growing room....wife may throw me out and keep the orchids!

Some from seedlings and a few in spike...if they survive may have some pics to post as a proud new orchid stepdad!

[Leafmite]

I am a believer in eggshells. The problem with using them is that people expect instant results and it takes some time for them to decompose enough to begin leeching Calcium to provide a steady source for the orchids. In the meantime, one must provide the orchids with another source. Not all orchids need the extra Calcium but I find Cattleyas and Angraecums definitely benefit from it. I wash the eggshells I use in cooking and use those. During the summer, when the plants are outside, I add powdered milk to my watering can.

The reason I am committed to extra Calcium is because I lost many very nice Cattleyas, many years ago, to Calcium deficiency. Unfortunately, at the time, there was no information about Calcium deficiency with orchids online and it was a terrible experience. I deduced what was happening from one of my houseplant books and experience with growing tomatoes. The extra Calcium ensures that I never really need to worry about fungus issues, even if it rains for three weeks and the temperatures are in the mid-sixties 'F.