It grows well, albeit kind of slow in my experience. It grows like a stem plant, as you can cut off the top and multiple new shoots will come up from that point. It doesn't spread via runners, but you can clip and replant if you want it to cover more area. It works great as a transition plant (not sure if that's the proper terminology) --- basically saying that instead of having a short foreground plant (HC, glosso) moving right into stem plants or taller plants like blyxa japonica, you can use the lobelia cardinalis as a transition. One of the uses it has is to cover up roots of plants behind it.
They do grow medium slow and is a nice fore to mid ground plant (transitional is a good description). Not too hard to grow, as long as basics are there - CO2, ferts, enough light. I have some two or three month old small forms (from cuttings) well over 3 inches tall.