dahlias, previously started indoors, to the garden outside? Are they super delicate?
In my experience, they are pretty tough and handle transplanting really well.
depends on, how pampered they where. If they never got direct sunlight their older leaves might get burnt, but they should produce new ones really fast.
I transferred some Dahlias 2 days ago, about 4-8 inches high, they looked fine yesterday. I had put them on the balcony frequently, when the weather wasnt too cold.
Just mind the slugs, then everything should be fine.
They are pretty dang tough. I always bury mien deeper in the ground then I grew them in their starting pots and they looked sad for about a day and the next they looked great.
Hardening off is another subject. Like said above, a few leaves might get burned, but very unlikely you will loose a plant. Just and FYI, if you snap off new growth by accident, try putting it in the ground too, you may get it to root and have more plants!