How can I motivate the tyme (moss) in my yard to grow?

Question:I have flagstone in my front yard and my parents planted moss in-between the cracks. they've been growing a little but not enough to fill in the cracks. how can we "motivate" them to grow the way we would like with out a landscaper?

Answers:
When trying stimulate growth.Moss is a very slow growing plant(lichen)Although slow growing,it propagates quite quickly.Need to be careful not walk(crush)on it.It thrives on dampness.So at nightfall it is good to spray with water,liberally.Does'nt like direct sunlight