Should I begin already to prune to encourage the eventual hedge shape?

They will look best with a prune every year, but when young the lighter the better, until they get very well established root systems. Let them build up some strength first. The best hedges I have seen get pruned hard every year, down to about 18". This after they have settled in for two or three years. Then after every flush of bloom cut them back lightly but evenly for the hedge effect. You can use hedge trimmers if they produce a clean cut.

Hard pruning I would not do to any other rose. 'Iceberg' seems to take it just fine, in Southern California.

These get pruned to 12-18" every January:

What is your climate zone?

What do you have in mind by "eventual hedge shape"? The natural form of Iceberg is somewhat arching and wide, generally considered an attractive feature/

I'm in zone 6b I believe.

I'm not looking for these to grow into a well-manicured hedge. I have them along a picket fence now, so I'm hoping to get them to look like the picture posted by hoovb above.

I guess what I wondered simply how long to wait to get them established before I do any "real" pruning.

All of my plants are about knee to thigh high, but have many very thin canes.

In zone 6 I wouldn't do any pruning now. In the spring just take out dead/damaged wood and let them grow some more. You can always prune for shaping during the season when you dead head. Then, maybe, the following spring take them down some and let them grow back and fill in more. They need some time to establish themselves and grow some good healthy root balls before you do any deep pruning.

I have a row that I planted last year from 1g pots that I plan to use as a loose informal hedge. I do not think I will do any pruning on them this year. After that I will probably only prune out anything dead or too tall and pretty much let them be.

Around here the shopping centers mow-blow guys leave about 18" to 2 feet when they prune and they sure bounce back well to about 36"

Understood about the not pruning now. I was planning on spring for maintenance, as this is normally when I prune my roses.

I was just looking at them the other day as was thinking "hmmmm I wonder what to with them this spring." And so, I posted the question.

Thanks for all the replies!

I agree with the feed and water the first year before heavy pruning in later years. Enjoy your plants. Iceberg should get a So. CA flower special award. It has a huge popularity here.