This forum is reserved for plant swaps. The best forum for you question would be the Geranium Forum. Surely there would be many experts, with loads of experience, that could answer your questions in detail there. Actually, if you searched the forum first, you'd probably find that your question had been asked and answered there multiple times.

Oops, sorry, I jumped forums some way. I didn't realize what forum I was in! You should still check the Geranium Forum, but I'm sure people here could help too.

To try to make up for my mistake, I will give you some links to previous answers to this question:

http://forums.gardenweb.com/forums/load/geranium/msg101622205552.html?10

http://www.gardengatemagazine.com/extras/77overwintering.php

http://forums.gardenweb.com/forums/load/geranium/msg061206128403.html?4

http://forums.gardenweb.com/forums/load/geranium/msg1011423219429.html?5

http://forums.gardenweb.com/forums/load/geranium/msg0803310932087.html?5

There's quite a bit of info in those posts, but if you still have questions, the posts above are just "the tip of the iceburg" in the Geranium Forum.

in my zone 5 ... i have NEVER succeeded in this.. and gave up ....

my uncle had a MICHIGAN BASEMENT at his cottage.. and did it all the time ...

i presumed that the dirt floor and natural stone somehow tempered the heat and humidity of winter ... in a way that i could not duplicate in my cement, furnace blasting basement.. no matter how i tried to manipulate the variables...

i gave up .. good luck to you ... ken

The only way I know of is to just keep them growing