There are several invasive species of sedum. You might check on google; search on sedum invasive, and you will get numerous links with pictures.

Thanks! I have only 5 or so that I've seen...they almost look like the one's I just put out in my rock garden that I collected from a friend.

Vera

Sounds like purslane (a weed)???

Marie

Here is a link that might be useful: Pic of Purslane

Oh no it's definatley not purslane...yuck! This looks exactly like a sort of sedum..growns in a cluster like round shape and is a succulent....

Vera

I was searching and searching to find a variety of sedum I have seen in a nursery lately, but could not find it. It sounds like what you are describing. However, I did find this great site for rock garden plants, that has an amazing list of sedum...

Here is a link that might be useful: rock garden plants -- sedum