I thought they should Barbara, but I dead head mine so they keep flowering. I suppose you could scatter seed in spring where you wouldn't mind them growing. My MiL's neighbour sprinkled some mixed seeds back in spring and she has got cosmos triffids!
‘The secret of being happy is being obsessed by something’ – David Bellamy
Interesting JasmineBarbara, I've never been able to grow them by scattering the seeds either and we dead head as well to keep the flowers coming for as long as we can.
Go placidly amidst the noise and the haste, and remember what peace there may be in silence.
I didn't do any /much dead heading of them this year, so maybe that's the reason they're still going strong, I'll have to put the wallflowers somewhere else this year.
maybe life didn't turn out to be the party you thought, but while your here you may as well dance