That's a good idea about letting the container cool down before snapping the cap on it. Great idea!
I am going to try my hand at freezing pollen again because the order I received recently from Maryott's has several of the cultivars sending up scapes. I want to have that pollen to use in the Spring. So I will be trying my hand at it again. I plan to take some notes this time as to what I did and whether is was successful (in pollinating some Spring blooms).
