The enemy of pollen is moisture; contained in the atmosphere, as well as the tissues of anthers and pollen sacs, and which can condense during freezing and thawing.
I've read a lot of stories outlining extremely tedious storage methods involving gelatin capsules, cotton balls and paint brushes or Q-Tips, but have had very good luck with a very simple method.
I used 35mm film containers, which are always handled and stored upside down, so that the lid functions as the pollen tray, and the body acts as a cap.
I place pollen sacs on sheets of paper to dry for a day, then label the film canister with the name of the pollen. The film canister lid and body are placed in the freezer, and left opened to chill and simultaneously dry. (The air inside a modern freezer is quite dry)
After 5-10 minutes, I put the dry pollen sacs inside the lid of the canister, then close the freezer door So that they will quickly freeze. After another 5 minutes, I crack open the freezer, and quickly put the body of the canister over the lid, and snap it closed. This helps to ensure that warm moist air isn't trapped inside the canister.
When it's time to use the pollen, I take the canister out of the freezer, let it reach room temperature, then open it. The pollen sacs are easily reached, and easy to handle with small hemostats. I've used the pollen a year later, and it is as fertile as if it were fresh.
Since film canisters aren't readily available anymore, a similar small container would need to be found.
