Per special request...
I was going to do a more formal write up but meh, too much going on and lack of motivation LOL.
Prior to freezing pollen I dehydrate it. This removes most of the moisture, preventing much of the damage associated with the process.
Now, Ill be honest... I've not done any controlled experiments to see if this if it is really required. I just know it works and works well.
So far I have frozen pollen for over 16 months and proven it is still viable. Luca has pollenated one of his helis using pollen of mine that was in excess of one year old.
Its very, very simple :-)
After harvesting the pollen, I immediately place it into micro-centrifuge tubes. I then take the tubes and place them (tops open) into a container of Silica desiccant. I then place the desiccant container in the fridge for two days. (tubes open, desiccant closed)
Then, I open the desiccant container and immediately close the micro centrifuge tubes and place those into another container and place in the freezer.
Residential refrigerators go through a defrost cycle every day or two. Placing the micro-centrifuge tubes into a larger container gives them added temp buffering during this defrost cycle.
Tubes in desiccant:
Notice in the picture I use two types of desiccant. The orange changes color when it's time to recharge them. They turn from orange to green. The white desiccant is not color indicating.
The container I use for the freezer is the same thing, just no beads. I just toss the tubes into it and close up the lid.
Be sure to mark the tubes.... its easy to forget what is what very quickly.
Oh and prior to opening the tubes for use.... let them gently come up to room temperature or you will get condensation on the pollen grains, which is not good at all.
I'll add the details of growing pollen tubes in a few days...