Hi Duke105077,
I don't grow
Anise Hyssop (Agastache foeniculum) but I'd think pruning in spring after all chance of frosts and freezes would be the best time.
I googled to see if I could find any information about pruning and found this article that says to prune a young plant in spring for a bushier specimen or cut the plant back in late winter to allow new stems to emerge the following spring.
http://www.gardeningknowhow.co... and on this page it says to cut back as needed and to cut back to 1" above the soil in fall.
http://www.seattleurbanfarmco....
This page says if you plan to dry the leaves, snip them 6" above the ground:
http://naturehacks.com/tips-fo...
Hopefully members who grows these beauties will pop in with advice!
