What is the best time to plant sunflower seeds outside? Do I have to wait
until after last frost or can I plant them sooner, like when soil is
workable? I'm pretty far up north and still easily hit -5°C at night but
getting up into high teens during the day now... finally!!
Any suggestions appreciated.

I'm down in Zone 6, SW Ohio USA and our sunflowers started coming in a few
weeks ago. They were all "volunteers" though -- apparently the birds didn't
quite eat all the seeds in the feeders after all. We must have had a
million seedlings under the feeders. Chuckle FWIW, we ended up mowing
them down since it was kinda in the lawn, but a few were also dropped in my
planters under the tree so we'll probably transplant those. By the time
they started growing, temps were consistently above freezing every night
(although we've had a snap to a few degrees F below freezing, but not often
or by much).

James