I did not use a heat mat either and mine were up in about two weeks. I am going to start some more in the closet. The seeds and seedlings are so small I would have a hard time keeping up with them outside!
I have a VERY old heat mat that I still use for some of the seeds that take longer. However, the mat is not necessary after that and only make the seedlings leggier. Some of my seeds did not need the heat mat, so it's really just a matter of patience!
Today they have tiny leaves. Since before this spring I never grew any flower from seed I am in complete fascination of the growing process. I have begun a journal to keep track of what I do right- and wrong so I don't do it again. My biggest problem is with hardening off. Quite windy here - never really noticed it till I set 2 flats out- put them in a shady corner against a north fence yet found them later flattened by the wind. Put them in the garage under the shop light- hope they will recover. Guess I'll have to devise a cold frame. Wish I had room for a greenhouse but have so many trees where there is actually room for it. Any other suggestions out there? Thanks, Susan