Hi Ned I believe this is the native Cenchrus purpurascens. You said 5 plants. I would appreciate some photos of the other plants growing nearby, especially photos showing the whole plant, so we can see the habit. It is similar to C. setaceus, a nasty weed.
Thanks Michael, I'll go get some more photos now. I counted five of the heads as a rough count in a couple of metres squared in the reeds at the edge of the wetland. I'll do a proper count today of how many actual plants there were because I think some of the heads came from the same plant. Thanks, Ned