Eucalptus, Silver Dollar

I have planted several Silver Dollar Eucalyptus plants in our garden in Brooks, Alberta, Canada for the second year in a row. The plants are doing quite nicely and we would like to harvest the branches for decoration this winter.
My questions are:
1. When should the branches be harvested?
2. What type and what amount of preservative is used to maintain the foliage?

You can harvest branches as soon as the trees are large enough to have enough leaves so that the loss of a few won't set them back too badly. The leaves are so succulent that they don't need to be preserved to retain their shape for quite some time even if kept out of water. To retain the best shape for dried arrangements, bury the branches in kitty litter in the shape you want them to rhave when dry. Check for dryness once a week by carefully removing the top of the kitty litter.
You can also dry the branches by suspending them top down with some string in a dry, airy, preferably dark place.