Is the moss growing "on" anything for the wreath base? I build outdoor garden fairy houses and tried to get moss to live on them, but so far it always goes brown and dies. Haven't quit trying yet. When I have settled for using dead moss I get fluorescent green spray paint and spray paint the moss - it sounds too vivid, but it is the right color once it is applied. Then, although it dies it looks alive... so it is a compromise you can perhaps make for your wreaths. I have a 10 x 15 ish foot moss garden where moss grows beautifully and here I have been able to squish dirt onto crevices of a log and on rocks and get moss to take off and multiply, so perhaps you just need to figure out the right base for the wreath for the moss to cling to and actually live on.