yes, those crystals do work in hanging pots, but not for 3 weeks.
INgrid

You can actually buy large quantities and put them in the ground.... What that
does to the environment I have no clue but it is possible to do. I love them in
my window boxes, the plants bake out there in the sun all day, and I can get
away with watering every other day if I need to, other wise they need it twice
a day... admittedly I have a little more then suggested in my pots lol. I have
to water my boxes because the rain doesn't reach.
Colleen
zone 5 Connecticut