Gardening observations - flowers in the sidewalk cracks?

This weekend I put in about 3 hours planting caladiums and annuals in our front flowerbed.  I had my IPhone tuned to Pandora in my shirt pocket, and my mix is a lot of piano jazz, so it was a lovely breezy morning, not too hot yet.  I had to do a lot of bed cleanout, pruning, and leaf raking too (filling almost a whole trash bag).  One thing I noticed was how easily weeds grow in those little grooves between the sidewalk and the curb.  Just little bits of soil and moisture get in there, but those weeds just really root down and get well-established (and hard to pull out).  Which leads me to a hypothesis that if I wanted to start some flowers or vegetables from seed in the spring, I should skip all those special seed-starter pots and systems, and just dribble those little seeds in those cracks by the road side, and just see what happens!