And this is the condition of my Costco tulips three weeks after the first bloom - and as it appeared in my 11/6/06 PAD http://www.pbase.com/ed_k/image/69918414
This is essentially straight from the camera (except for some dodging of the background to get it completely white). It was getting dark (note the 20 sec exposure time) and I silhouetted the tulip against the sky that still had some light in it. Next I spot metered on the darkest part of the flower - guaranteeing that it would be properly exposed and the background highlights blown out to pure white. Finally for good measure I over exposed (EV+1.5) further guaranteeing a white background (and with all of this there were still a few light gray areas from trees in the distance - but I dodged these to pure white). More than you wanted to know....
I guess the easier way to do this is to just put something white behind the tulip - but then it wouldn't be an experiment.