I have a small paved front garden,with Aliums in pots placed around it, I'd like to know,is what's best for them once the flowers have faded,do I leave them in the pots,put the pots in the back garden,let them die down,& put them back out next year,if so will I be able to get seeds scattered from them around the back garden,or do I need to take them out of the pots.Any answers would be much appreciated