You can't. They will wilt and die every single time. The best time to do it is in the house or in a greenhouse. They will do alot better. If you have to do it outside, do it in a pot at first. That way you can move them out of the heat if you have to.
this is how you propagate hydrangea it likes heat around 70- 75 and where the roots are it should stay around 60 if you want to do stem cutting to replant more cut around 2 inches off
