Well, They do have plastic peices just for that type of thing, but have never used it. How about stone, or concreat? They have those pre-cast reatining wall blocks. Not real cheep, but would last FOREVER. Or if you don;t mind rebuilding it every few years, just use pine and replace it alot. Or bite the bulit and use the cypress. She will be happy, [remember, she's happy, your happy ] and it would last a LONG time. That stuff is awsome. To bad I can't get it where I am.