Sorry if My Id is correct as this is a weed, but it can be eaten sparingly as a green in salad or steamed it is supposively rich in Iron and Omega 3, but I've never tasted it.
Michael M, I have doubts about this being Portulaca oleracea, which grows in my garden and is an annual and doesn't reach the stage seen above until summer. I think this is Lythrum hyssopifolia, especially since it is growing near a dam an is partly erect.
Lythrum hyssopifola has narrow to very narrow leaves. When it has has red stems it is obviously stressed and the leaves are red also. The stems of the plant in this photo look fleshy, true for Portulaca, untrue for Lythrum.
I'm sorry to contradict you Betty, but it is virtually impossible for it to be Portulaca oleracea in October. Also Look at the following sightings, which have fleshy looking leaves of similar shape: http://canberra.naturemapr.org/Community/Sightings/Details/34758 http://canberra.naturemapr.org/Community/Sightings/Details/31544
I am sorry, don't trust my memory in that respect...Lythrum h. did cross my mind but the leaves seemed extremely round for that. I will see if I can find it again this season, but it might well be too dry. Is it possible that the extreme rain last year might have had this grow much earlier than usual?
This is not very scientific, but googling Lythrum hyssopifolia does yield a number of images that are identical to mine (e.g. http://calphotos.berkeley.edu/cgi/img_query?enlarge=0000+0000+0411+1060) and they seem to be taken in very wet spots. Maybe the thing is that the Lythrum h. was looking unusual due to the heavy rains?