I think I read somewhere that they need to be about 6' apart, but I'm not sure.  I don't know how you could be sure they aren't cross-pollinated when you have flying insects flying all around your yard. 

I have 2 JMGs that I started indoors.  They're growing in small pots and vining up my shelf.  The first one has gotten all the way to the top of the shelf and it opened it's first bloom this morning!  It's a white one.  It think it's supposed to have a pale yellow throat, but I didn't have a chance to inspect it closely this morning.  The other one sprouted a lot later, so it's just now starting to vine.  But it has variegated leaves and is supposed to have blue flowers.  I can't wait to see it!  My red ones didn't sprout.  :(  I've got a couple more seeds of that one, so it's time to try again!

I planted a bunch of different regular MGs and Moonflowers outside over the weekend.  I had so many that I planted what I could in the few spots in my yard where they'll be able to climb, then planted all the rest in the weedy area across the street.  Since they do grow like weeds here, I'm hoping they'll take over that area, & I'll have a curtain of MGs by summer!  It'll be so much prettier to look at instead of all the ugly weeds that normally grow there.  I put some in the ground, then tossed the rest into the weeds, so hopefully at least some of them grow.
--Sharry