Ludwigia Repens-How close to plant?

I have a moderately planted 29 gal tank, and recently recieved 50 stems of ludwigia repens to add to it. I want to add it on the right wall, in a diagonal, beginning at the front corner & ending 1/3 of the way across the back, just behind a piece of driftwood. (I hope that makes sense...) I know this is a very common plant, but I've never had ludwigia in my tank before, so how close should I plant them? I would like a thicket of them, but will the roots rot if I put them too close together?

Thanks in advance!