Adjust pH of agar????
 

Total noob here. Basic question is, do I need to adjust the pH of agar when flasking seeds, and if so, how and to what pH? Details - I have a couple of pink and yellow ladyslipper pods from plants that grow on my property in central Virginia USA. I plan to use distilled water with T849 with coconut water, and M551 with sucrose. I can't seem to find out much about this pH question when kicking around this forum. Details about me - I love native plants and enjoy growing them on my place. In the last couple of years I also started the hobby of cloning and growing local and gourmet mushrooms, raising them in sawdust bags in my basement. Growing mushrooms turns out to use most of the same equipment and skills that propagating orchids from seed uses. Anyway, I'd greatly appreciate any advice I can get here - thanks!

Media formulations are generally buffered to a specific range - 4.25 ± 0.5 for M551 and 5.25 ± 0.5 for T849, according to the Phytotech website. Other sources might vary somewhat. They may come with a certificate of analysis that tells what pH was found in testing. Unless you have an additive with a very strong pH or buffering of its own the buffering of the media should hold.

You can prepare the media and test/adjust pH before dispensing and sterilizing. Most often 1N HCl or 1N NaOH would be used to adjust pH, or somewhat more or less dilute solutions would obvious also work. What pH you want for your use is harder to say, and I'm sure there are divergent recommendations. Since both media are intended for terrestrial orchids they are probably reasonable for your use as they are. Even better if you can test them and confirm the pH so at least you know what you have as a basis for future adjustments based on success.

It's better to adjust pH between 5.5 - 5.8 in tissue culture. For terrestrial orchids, some prefer Terrestrial Orchid Medium w/out NH4NO3.

See the following link for more information:
About Orchids