We have a concrete slab patio in the backyard of our new home. The concrete has several cracks in it. We would like to plant a "crack garden"--plant some creeping thyme or other hardy plants in the cracks, but don't really know how to go about doing that. Do we need to widen the cracks so that we can put in some soil?

Can you think of other plants/flowers that might look good in a crack garden?

TIA