hey summer ....

no one has replied .... i dont know the answer ...

but do you have a greenhouse for this job ???

i see this as a full sun [not inside a window] plant that needs high humidity ....

rooting it .. might be the least of your problems.. should you succeed ... if you are simply playing around in the house ....

ken

I have a small backyard greenhouse that was built by a building contractor. I've heated it the past two winters. It heats with one or two small electric heaters. It's just a slightly expensive hobby for me--not a money making venture. I'm just going to have to experiment and see what works for petunias.

i googled : propagating petunia by cuttings

which led me to the link below ..

wherein it is said:

PROPAGATING PETUNIAS FROM CUTTINGS

Named varieties of petunias, especially the doubles, may be propagated by inserting cuttings in pots of sandy soil in a cold frame in September.

The rooted cuttings must be wintered in a greenhouse with a minimum temperature of 45 degrees

===>>> otherwise it seems that most peeps do it from seed ....

ken

Here is a link that might be useful: link