Ok so I'm on my 3rd year of trying to establish a flourishing bed of moss in between my flag stones.

The first year went decent but a LOT of handpicking of weeds!!! Last year the moss grew great...however the weeds were worse. They grew though all of the moss beds and made it look downright ugly. I made the HUGE mistake of using round up (read somewhere a certain roundup worked on weeds and would leave the moss) and it killed everything. On the bright side some Moss seed I laid down came back and as of right now I have some decent growth starting already.

I also bought more young moss plants and have just planted them in the more bare spots.

Now onto my question. I want to prevent weeds from growing before they become a problem this year. I've been told Preen will do the job. It will not harm any of the existing plants and will only interfere with germination of seeds. I'm assuming the moss will still spread but any seeds given off won't grow. That's fine.

But is this true? Does anyone else use this tactic with preen?

In any case how do you all prevent weeds in your moss besides having to hand pick. Hand picking is tiresome. I lost the battle last year when I was out of town for 5 days and came back to see the weeds had taken foothold. Then the round up came and blah. :(

Any help would be great! Overall I'm thinking about laying down some Preen right now. I figure once the Preen wears off weed season will be almost over and I can lay down moss seed. Once they moss seed grows decent I can put down a little more Preen.

Please advise!