It's an eight petal motif, and it's either joined by long chains or a chain type of motif. The link below is for joining motifs, I think the second set of instructions applies to this one. ;0)

As for hard to do, nope pretty easy, you just have to crochet a lot of motifs and either join as you go or wait until you get the amount you want done and join after.

Here is a link that might be useful: how to join crochet together