I thought I was going to have to start a new segment for this one under "Monday Mystery" because when I went on line to read about this plant, what was described and pictured was totally different. However, I've persevered and eventually found the right Dog Bane. I saw it at the Queensland Garden Expo and immediately thought it was fat lavender.
It is called dog bane because dogs don't like it apparently and it can be made into a spray to use as a repellent.