I've had seeds that have taken less than 12hrs to show root and in one not so great experience, I gave up on germination after 10 days (after 2 days in papertowel and 8 in soil) to toss the soil from abandoned pots out into garden which is about a foot from pavement and discover a couple of weeks later, a nice looking seedling emerging from soil quite happily in full view of anyone who walked past.