I always used egg shells in my potting soil for houseplants and outdoor plants. But orchids aren't grown in potting soil, and I found that they weren't working for the orchid media. I can't say if they did any good, so I stopped using them.

My Cat. and other orchids grow in bark /fern/perlite soil which I bought from local orchids store. Over the time, I put aayer of egg shell or tea bag on top of the soil loosely. but it seems to me the egg shell/tea bag does not have either positive or negitve effect on the grows of my orchids. They flower as usuall, grow new plant as usuall. I just curiouse if anyone out there has done what I did and can share either positive or negtive results. Does orchids need calcium to grow better at all?

I think there are some paphs (Brachys and Parvis mainly) that defintely like a more 'calcified' mix. The 'norm' is to use crushed oyster shells, but egg shells work also.

If you use a balanced fert, the general feeling is that additional calcium is not needed for most other orchids.

Bob