Posted: 19/07/2012 at 09:48
Sorry, Lorelei. I originally asked whether there was any justification for the American advice (they referred to preventing fungal attack and reducing seed-set) and proposed a simple experiment to see whether dead-heading would make any physiological, as opposed to cosmetic, difference to the plant.
Losing interest in the thread, I inadvertently wrote 'pruning' rather than 'dead-deading'. Needless to say, I do know the difference!
Thanks for Millais's advice, Grandma. Again, it would be interesting to know if it's backed up by any objective research. Obviously, they have an interest in offering plants that look good.