Hey, check out this thread
Northern Lights/Deciduous Azalea Thread for the most information. Having said that, I bought a Northern Hi-Lights Azalea last year and it's doing pretty good one year later. What I've found/done is that I will wait for them to finish flowering and then I will do a big repot and a big prune all at once. It's stressful on the plant, and I lose one of the three azaleas from last year (Electric Lights - Red) doing the repot and big prune, but my other two survived and are doing well this year.
Repot - I repotted mine into training boxes filled with Kanuma with some japanese moss on top and mixed in to the Kanuma mix at the top to help the roots along.
Big Prune - I pruned my Northern Hi-Lights back to just the branches, all the leaves gone, and in a couple of weeks it had grown all new leaves. So, moving forward, when I big prune an Azalea I'm training for bonsai, I plan to prune all the way back to the good structured branches. Keep the good structure to build off of, prune off all the rest, and just set yourself up to get a little better year by year.
One one of my plants I didn't do a "Big Prune", and I did a 50% prune instead, and the plant didn't really shoot out any new growth, it just rode the remainder of the year out with what it had. Which was kind of disappointing. I will be doing a big prune on that plant this year and essentially taking it down to the Trunk.
Good luck and keep us posted on your progress on that other thread!
