Cold weather crops like your broccoli and cabbage dont really like heat mats : )

Rule of Thumb: if it can take some frost or you plant it out earlier then tomatoes, it doesn't need heat.

Keriann~

I started mine on a mat but watched them very closely. They were breaking through in 36 to 48 hours, at that point i took them off the heat and placed under lights.

This is my first year using heat so I know little about it, but all is well so far. My Royal Hillbilly Tomatoes did not come up but all others did. I expect bad seed.

Most mats are controlled at 70 degrees and the temperature is not the problem, the time is. Gardeners read the packet which says germination should take up to 21 days, and are not prepared for many seeds starting in 3 days, when they should be taken off the heat. Al

Thanks for all the advice. Maybe I'll pop the broccoli and cauliflower on the heat mat briefly and keep a close watch on them.

Yep, the heat should be turned off as soon as germination takes place.